Merge remote-tracking branch 'upstream/main' into dev/dawengie/CodeActionsPart5

eng/Version.Details.xml

@@ -6,9 +6,9 @@
       <Sha>839cdfb0ecca5e0be3dbccd926e7651ef50fdf10</Sha>
     </Dependency>
     <!-- Intermediate is necessary for source build. -->
-    <Dependency Name="Microsoft.SourceBuild.Intermediate.source-build-reference-packages" Version="10.0.0-alpha.1.24521.1">
+    <Dependency Name="Microsoft.SourceBuild.Intermediate.source-build-reference-packages" Version="10.0.0-alpha.1.24530.1">
       <Uri>https://github.com/dotnet/source-build-reference-packages</Uri>
-      <Sha>ccd0927e3823fb178c7151594f5d2eaba81bba81</Sha>
+      <Sha>136e43e45e20bd58bf86eeabba0a0fa7e1a4b3ae</Sha>
       <SourceBuild RepoName="source-build-reference-packages" ManagedOnly="true" />
     </Dependency>
     <Dependency Name="Microsoft.Net.Compilers.Toolset" Version="4.13.0-2.24554.8">

eng/Versions.props

@@ -49,7 +49,7 @@
   <PropertyGroup Label="Automated">
     <MicrosoftNETCoreBrowserDebugHostTransportPackageVersion>6.0.2-servicing.22064.6</MicrosoftNETCoreBrowserDebugHostTransportPackageVersion>
     <MicrosoftNETCorePlatformsPackageVersion>6.0.1</MicrosoftNETCorePlatformsPackageVersion>
-    <MicrosoftSourceBuildIntermediatesourcebuildreferencepackagesPackageVersion>10.0.0-alpha.1.24521.1</MicrosoftSourceBuildIntermediatesourcebuildreferencepackagesPackageVersion>
+    <MicrosoftSourceBuildIntermediatesourcebuildreferencepackagesPackageVersion>10.0.0-alpha.1.24530.1</MicrosoftSourceBuildIntermediatesourcebuildreferencepackagesPackageVersion>
     <MicrosoftSourceBuildIntermediatearcadePackageVersion>9.0.0-beta.24516.2</MicrosoftSourceBuildIntermediatearcadePackageVersion>
     <MicrosoftDotNetXliffTasksPackageVersion>1.0.0-beta.23475.1</MicrosoftDotNetXliffTasksPackageVersion>
     <MicrosoftSourceBuildIntermediatexlifftasksPackageVersion>1.0.0-beta.23475.1</MicrosoftSourceBuildIntermediatexlifftasksPackageVersion>

eng/targets/Services.props

@@ -33,6 +33,7 @@
     <ServiceHubService Include="Microsoft.VisualStudio.Razor.GoToImplementation" ClassName="Microsoft.CodeAnalysis.Remote.Razor.RemoteGoToImplementationService+Factory" />
     <ServiceHubService Include="Microsoft.VisualStudio.Razor.SpellCheck" ClassName="Microsoft.CodeAnalysis.Remote.Razor.RemoteSpellCheckService+Factory" />
     <ServiceHubService Include="Microsoft.VisualStudio.Razor.Diagnostics" ClassName="Microsoft.CodeAnalysis.Remote.Razor.RemoteDiagnosticsService+Factory" />
+    <ServiceHubService Include="Microsoft.VisualStudio.Razor.Hover" ClassName="Microsoft.CodeAnalysis.Remote.Razor.RemoteHoverService+Factory" />
     <ServiceHubService Include="Microsoft.VisualStudio.Razor.Completion" ClassName="Microsoft.CodeAnalysis.Remote.Razor.RemoteCompletionService+Factory" />
     <ServiceHubService Include="Microsoft.VisualStudio.Razor.CodeActions" ClassName="Microsoft.CodeAnalysis.Remote.Razor.RemoteCodeActionsService+Factory" />
   </ItemGroup>

src/Razor/src/Microsoft.AspNetCore.Razor.LanguageServer/RazorLanguageServer.cs

@@ -130,7 +130,6 @@ internal partial class RazorLanguageServer : SystemTextJsonLanguageServer<RazorR
         services.AddDocumentManagementServices(featureOptions);
         services.AddFormattingServices(featureOptions);
         services.AddOptionsServices(_lspOptions);
-        services.AddHoverServices();
         services.AddTextDocumentServices(featureOptions);
 
         if (!featureOptions.UseRazorCohostServer)
@@ -157,6 +156,9 @@ internal partial class RazorLanguageServer : SystemTextJsonLanguageServer<RazorR
             services.AddSingleton<IRazorFoldingRangeProvider, UsingsFoldingRangeProvider>();
 
             services.AddSingleton<IFoldingRangeService, FoldingRangeService>();
+
+            // Hover
+            services.AddHoverServices();
         }
 
         // Other

src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Extensions/ClientCapabilitiesExtensions.cs

@@ -0,0 +1,31 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the MIT license. See License.txt in the project root for license information.
+
+using System;
+
+namespace Microsoft.VisualStudio.LanguageServer.Protocol;
+
+internal static class ClientCapabilitiesExtensions
+{
+    public static MarkupKind GetMarkupKind(this ClientCapabilities clientCapabilities)
+    {
+        // If MarkDown is supported, we'll use that.
+        if (clientCapabilities.TextDocument?.Hover?.ContentFormat is MarkupKind[] contentFormat &&
+            Array.IndexOf(contentFormat, MarkupKind.Markdown) >= 0)
+        {
+            return MarkupKind.Markdown;
+        }
+
+        return MarkupKind.PlainText;
+    }
+
+    public static bool SupportsMarkdown(this ClientCapabilities clientCapabilities)
+    {
+        return clientCapabilities.GetMarkupKind() == MarkupKind.Markdown;
+    }
+
+    public static bool SupportsVisualStudioExtensions(this ClientCapabilities clientCapabilities)
+    {
+        return (clientCapabilities as VSInternalClientCapabilities)?.SupportsVisualStudioExtensions ?? false;
+    }
+}

src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Hover/HoverDisplayOptions.cs

@@ -1,7 +1,6 @@
 // Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the MIT license. See License.txt in the project root for license information.
 
-using System;
 using Microsoft.VisualStudio.LanguageServer.Protocol;
 
 namespace Microsoft.CodeAnalysis.Razor.Hover;
@@ -10,16 +9,8 @@ internal readonly record struct HoverDisplayOptions(MarkupKind MarkupKind, bool
 {
     public static HoverDisplayOptions From(ClientCapabilities clientCapabilities)
     {
-        var markupKind = MarkupKind.PlainText;
-
-        // If MarkDown is supported, we'll use that.
-        if (clientCapabilities.TextDocument?.Hover?.ContentFormat is MarkupKind[] contentFormat &&
-            Array.IndexOf(contentFormat, MarkupKind.Markdown) >= 0)
-        {
-            markupKind = MarkupKind.Markdown;
-        }
-
-        var supportsVisualStudioExtensions = (clientCapabilities as VSInternalClientCapabilities)?.SupportsVisualStudioExtensions ?? false;
+        var markupKind = clientCapabilities.GetMarkupKind();
+        var supportsVisualStudioExtensions = clientCapabilities.SupportsVisualStudioExtensions();
 
         return new(markupKind, supportsVisualStudioExtensions);
     }

src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Remote/IRemoteHoverService.cs

@@ -0,0 +1,19 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the MIT license. See License.txt in the project root for license information.
+
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis.ExternalAccess.Razor;
+using RoslynHover = Roslyn.LanguageServer.Protocol.Hover;
+using RoslynPosition = Roslyn.LanguageServer.Protocol.Position;
+
+namespace Microsoft.CodeAnalysis.Razor.Remote;
+
+internal interface IRemoteHoverService : IRemoteJsonService
+{
+    ValueTask<RemoteResponse<RoslynHover?>> GetHoverAsync(
+        JsonSerializableRazorPinnedSolutionInfoWrapper solutionInfo,
+        JsonSerializableDocumentId documentId,
+        RoslynPosition position,
+        CancellationToken cancellationToken);
+}

src/Razor/src/Microsoft.CodeAnalysis.Razor.Workspaces/Remote/RazorServices.cs

@@ -30,6 +30,7 @@ internal static class RazorServices
         [
             (typeof(IRemoteClientInitializationService), null),
             (typeof(IRemoteGoToDefinitionService), null),
+            (typeof(IRemoteHoverService), null),
             (typeof(IRemoteSignatureHelpService), null),
             (typeof(IRemoteInlayHintService), null),
             (typeof(IRemoteDocumentSymbolService), null),

src/Razor/src/Microsoft.CodeAnalysis.Remote.Razor/Hover/RemoteHoverService.cs

@@ -0,0 +1,215 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the MIT license. See License.txt in the project root for license information.
+
+using System.Diagnostics;
+using System.Linq;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Razor;
+using Microsoft.AspNetCore.Razor.Language;
+using Microsoft.CodeAnalysis.ExternalAccess.Razor;
+using Microsoft.CodeAnalysis.Razor.DocumentMapping;
+using Microsoft.CodeAnalysis.Razor.Hover;
+using Microsoft.CodeAnalysis.Razor.Protocol;
+using Microsoft.CodeAnalysis.Razor.Remote;
+using Microsoft.CodeAnalysis.Remote.Razor.ProjectSystem;
+using Roslyn.LanguageServer.Protocol;
+using static Microsoft.CodeAnalysis.Razor.Remote.RemoteResponse<Roslyn.LanguageServer.Protocol.Hover?>;
+using static Microsoft.VisualStudio.LanguageServer.Protocol.ClientCapabilitiesExtensions;
+using static Microsoft.VisualStudio.LanguageServer.Protocol.VsLspExtensions;
+using static Roslyn.LanguageServer.Protocol.RoslynLspExtensions;
+using ExternalHandlers = Microsoft.CodeAnalysis.ExternalAccess.Razor.Cohost.Handlers;
+using Range = Roslyn.LanguageServer.Protocol.Range;
+using VsLsp = Microsoft.VisualStudio.LanguageServer.Protocol;
+
+namespace Microsoft.CodeAnalysis.Remote.Razor;
+
+internal sealed class RemoteHoverService(in ServiceArgs args) : RazorDocumentServiceBase(in args), IRemoteHoverService
+{
+    internal sealed class Factory : FactoryBase<IRemoteHoverService>
+    {
+        protected override IRemoteHoverService CreateService(in ServiceArgs args)
+            => new RemoteHoverService(in args);
+    }
+
+    private readonly IClientCapabilitiesService _clientCapabilitiesService = args.ExportProvider.GetExportedValue<IClientCapabilitiesService>();
+
+    protected override IDocumentPositionInfoStrategy DocumentPositionInfoStrategy => PreferAttributeNameDocumentPositionInfoStrategy.Instance;
+
+    public ValueTask<RemoteResponse<Hover?>> GetHoverAsync(
+        JsonSerializableRazorPinnedSolutionInfoWrapper solutionInfo,
+        JsonSerializableDocumentId documentId,
+        Position position,
+        CancellationToken cancellationToken)
+        => RunServiceAsync(
+            solutionInfo,
+            documentId,
+            context => GetHoverAsync(context, position, cancellationToken),
+            cancellationToken);
+
+    private async ValueTask<RemoteResponse<Hover?>> GetHoverAsync(
+        RemoteDocumentContext context,
+        Position position,
+        CancellationToken cancellationToken)
+    {
+        var codeDocument = await context.GetCodeDocumentAsync(cancellationToken).ConfigureAwait(false);
+
+        if (!codeDocument.Source.Text.TryGetAbsoluteIndex(position, out var hostDocumentIndex))
+        {
+            return NoFurtherHandling;
+        }
+
+        var clientCapabilities = _clientCapabilitiesService.ClientCapabilities;
+        var positionInfo = GetPositionInfo(codeDocument, hostDocumentIndex, preferCSharpOverHtml: true);
+
+        if (positionInfo.LanguageKind == RazorLanguageKind.CSharp)
+        {
+            var generatedDocument = await context.Snapshot
+                .GetGeneratedDocumentAsync(cancellationToken)
+                .ConfigureAwait(false);
+
+            var csharpHover = await ExternalHandlers.Hover
+                .GetHoverAsync(
+                    generatedDocument,
+                    positionInfo.Position.ToLinePosition(),
+                    clientCapabilities.SupportsVisualStudioExtensions(),
+                    clientCapabilities.SupportsMarkdown(),
+                    cancellationToken)
+                .ConfigureAwait(false);
+
+            // Roslyn couldn't provide a hover, so we're done.
+            if (csharpHover is null)
+            {
+                return NoFurtherHandling;
+            }
+
+            // Map the hover range back to the host document
+            if (csharpHover.Range is { } range &&
+                DocumentMappingService.TryMapToHostDocumentRange(codeDocument.GetCSharpDocument(), range.ToLinePositionSpan(), out var hostDocumentSpan))
+            {
+                csharpHover.Range = RoslynLspFactory.CreateRange(hostDocumentSpan);
+            }
+
+            return Results(csharpHover);
+        }
+
+        if (positionInfo.LanguageKind is not (RazorLanguageKind.Html or RazorLanguageKind.Razor))
+        {
+            Debug.Fail($"Encountered an unexpected {nameof(RazorLanguageKind)}: {positionInfo.LanguageKind}");
+            return NoFurtherHandling;
+        }
+
+        // If this is Html or Razor, try to retrieve a hover from Razor.
+        var options = HoverDisplayOptions.From(clientCapabilities);
+
+        var razorHover = await HoverFactory
+            .GetHoverAsync(codeDocument, hostDocumentIndex, options, context.GetSolutionQueryOperations(), cancellationToken)
+            .ConfigureAwait(false);
+
+        // Roslyn couldn't provide a hover, so we're done.
+        if (razorHover is null)
+        {
+            return CallHtml;
+        }
+
+        // Ensure that we convert our Hover to a Roslyn Hover.
+        var resultHover = ConvertHover(razorHover);
+
+        return Results(resultHover);
+    }
+
+    /// <summary>
+    ///  Converts a <see cref="VsLsp.Hover"/> to a <see cref="Hover"/>.
+    /// </summary>
+    /// <remarks>
+    ///  Once Razor moves wholly over to Roslyn.LanguageServer.Protocol, this method can be removed.
+    /// </remarks>
+    private Hover ConvertHover(VsLsp.Hover hover)
+    {
+        // Note: Razor only ever produces a Hover with MarkupContent or a VSInternalHover with RawContents.
+        // Both variants return a Range.
+
+        return hover switch
+        {
+            VsLsp.VSInternalHover { Range: var range, RawContent: { } rawContent } => new VSInternalHover()
+            {
+                Range = ConvertRange(range),
+                Contents = string.Empty,
+                RawContent = ConvertVsContent(rawContent)
+            },
+            VsLsp.Hover { Range: var range, Contents.Fourth: VsLsp.MarkupContent contents } => new Hover()
+            {
+                Range = ConvertRange(range),
+                Contents = ConvertMarkupContent(contents)
+            },
+            _ => Assumed.Unreachable<Hover>(),
+        };
+
+        static Range? ConvertRange(VsLsp.Range? range)
+        {
+            return range is not null
+                ? RoslynLspFactory.CreateRange(range.ToLinePositionSpan())
+                : null;
+        }
+
+        static object ConvertVsContent(object obj)
+        {
+            return obj switch
+            {
+                VisualStudio.Core.Imaging.ImageId imageId => ConvertImageId(imageId),
+                VisualStudio.Text.Adornments.ImageElement element => ConvertImageElement(element),
+                VisualStudio.Text.Adornments.ClassifiedTextRun run => ConvertClassifiedTextRun(run),
+                VisualStudio.Text.Adornments.ClassifiedTextElement element => ConvertClassifiedTextElement(element),
+                VisualStudio.Text.Adornments.ContainerElement element => ConvertContainerElement(element),
+                _ => Assumed.Unreachable<object>()
+            };
+
+            static Roslyn.Core.Imaging.ImageId ConvertImageId(VisualStudio.Core.Imaging.ImageId imageId)
+            {
+                return new(imageId.Guid, imageId.Id);
+            }
+
+            static Roslyn.Text.Adornments.ImageElement ConvertImageElement(VisualStudio.Text.Adornments.ImageElement element)
+            {
+                return new(ConvertImageId(element.ImageId), element.AutomationName);
+            }
+
+            static Roslyn.Text.Adornments.ClassifiedTextRun ConvertClassifiedTextRun(VisualStudio.Text.Adornments.ClassifiedTextRun run)
+            {
+                return new(
+                    run.ClassificationTypeName,
+                    run.Text,
+                    (Roslyn.Text.Adornments.ClassifiedTextRunStyle)run.Style,
+                    run.MarkerTagType,
+                    run.NavigationAction,
+                    run.Tooltip);
+            }
+
+            static Roslyn.Text.Adornments.ClassifiedTextElement ConvertClassifiedTextElement(VisualStudio.Text.Adornments.ClassifiedTextElement element)
+            {
+                return new(element.Runs.Select(ConvertClassifiedTextRun));
+            }
+
+            static Roslyn.Text.Adornments.ContainerElement ConvertContainerElement(VisualStudio.Text.Adornments.ContainerElement element)
+            {
+                return new((Roslyn.Text.Adornments.ContainerElementStyle)element.Style, element.Elements.Select(ConvertVsContent));
+            }
+        }
+
+        static MarkupContent ConvertMarkupContent(VsLsp.MarkupContent value)
+        {
+            return new()
+            {
+                Kind = ConvertMarkupKind(value.Kind),
+                Value = value.Value
+            };
+        }
+
+        static MarkupKind ConvertMarkupKind(VsLsp.MarkupKind value)
+        {
+            return value == VsLsp.MarkupKind.Markdown
+                ? MarkupKind.Markdown
+                : MarkupKind.PlainText;
+        }
+    }
+}

src/Razor/src/Microsoft.VisualStudio.LanguageServices.Razor/LanguageClient/Cohost/CohostDocumentColorEndpoint.cs

@@ -32,7 +32,7 @@ internal class CohostDocumentColorEndpoint(
 
     protected override bool RequiresLSPSolution => true;
 
-    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, DocumentFilter[] filter, RazorCohostRequestContext requestContext)
+    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, RazorCohostRequestContext requestContext)
     {
         if (clientCapabilities.SupportsVisualStudioExtensions)
         {
@@ -40,9 +40,6 @@ internal class CohostDocumentColorEndpoint(
             {
                 Method = Methods.TextDocumentDocumentColorName,
                 RegisterOptions = new DocumentColorRegistrationOptions()
-                {
-                    DocumentSelector = filter
-                }
             }];
         }
 

src/Razor/src/Microsoft.VisualStudio.LanguageServices.Razor/LanguageClient/Cohost/CohostDocumentCompletionEndpoint.cs

@@ -55,7 +55,7 @@ internal sealed class CohostDocumentCompletionEndpoint(
 
     protected override bool RequiresLSPSolution => true;
 
-    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, DocumentFilter[] filter, RazorCohostRequestContext requestContext)
+    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, RazorCohostRequestContext requestContext)
     {
         if (clientCapabilities.TextDocument?.Completion?.DynamicRegistration is true)
         {
@@ -66,7 +66,6 @@ internal sealed class CohostDocumentCompletionEndpoint(
                 {
                     ResolveProvider = false, // TODO - change to true when Resolve is implemented
                     TriggerCharacters = CompletionTriggerAndCommitCharacters.AllTriggerCharacters,
-                    DocumentSelector = filter,
                     AllCommitCharacters = CompletionTriggerAndCommitCharacters.AllCommitCharacters
                 }
             }];
@@ -188,7 +187,7 @@ internal sealed class CohostDocumentCompletionEndpoint(
                 completionContext.TriggerCharacter);
         }
 
-        return combinedCompletionList; 
+        return combinedCompletionList;
     }
 
     private async Task<VSInternalCompletionList?> GetHtmlCompletionListAsync(
@@ -219,7 +218,7 @@ internal sealed class CohostDocumentCompletionEndpoint(
         return rewrittenResponse;
     }
 
-    private static T? ToVsLSP<T>(object source) where T : class 
+    private static T? ToVsLSP<T>(object source) where T : class
     {
         // This is, to say the least, not ideal. In future we're going to normalize on to Roslyn LSP types, and this can go.
         var options = new JsonSerializerOptions();

src/Razor/src/Microsoft.VisualStudio.LanguageServices.Razor/LanguageClient/Cohost/CohostDocumentFormattingEndpoint.cs

@@ -45,7 +45,7 @@ internal sealed class CohostDocumentFormattingEndpoint(
 
     protected override bool RequiresLSPSolution => true;
 
-    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, DocumentFilter[] filter, RazorCohostRequestContext requestContext)
+    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, RazorCohostRequestContext requestContext)
     {
         if (clientCapabilities.TextDocument?.Formatting?.DynamicRegistration is true)
         {
@@ -53,9 +53,6 @@ internal sealed class CohostDocumentFormattingEndpoint(
             {
                 Method = Methods.TextDocumentFormattingName,
                 RegisterOptions = new DocumentFormattingRegistrationOptions()
-                {
-                    DocumentSelector = filter
-                }
             }];
         }
 

src/Razor/src/Microsoft.VisualStudio.LanguageServices.Razor/LanguageClient/Cohost/CohostDocumentHighlightEndpoint.cs

@@ -38,7 +38,7 @@ internal class CohostDocumentHighlightEndpoint(
 
     protected override bool RequiresLSPSolution => true;
 
-    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, DocumentFilter[] filter, RazorCohostRequestContext requestContext)
+    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, RazorCohostRequestContext requestContext)
     {
         if (clientCapabilities.SupportsVisualStudioExtensions)
         {
@@ -46,9 +46,6 @@ internal class CohostDocumentHighlightEndpoint(
             {
                 Method = Methods.TextDocumentDocumentHighlightName,
                 RegisterOptions = new DocumentHighlightRegistrationOptions()
-                {
-                    DocumentSelector = filter
-                }
             }];
         }
 

src/Razor/src/Microsoft.VisualStudio.LanguageServices.Razor/LanguageClient/Cohost/CohostDocumentPullDiagnosticsEndpoint.cs

@@ -50,7 +50,7 @@ internal class CohostDocumentPullDiagnosticsEndpoint(
 
     protected override bool RequiresLSPSolution => true;
 
-    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, DocumentFilter[] filter, RazorCohostRequestContext requestContext)
+    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, RazorCohostRequestContext requestContext)
     {
         // TODO: if (clientCapabilities.TextDocument?.Diagnostic?.DynamicRegistration is true)
         {
@@ -59,7 +59,6 @@ internal class CohostDocumentPullDiagnosticsEndpoint(
                 Method = VSInternalMethods.DocumentPullDiagnosticName,
                 RegisterOptions = new VSInternalDiagnosticRegistrationOptions()
                 {
-                    DocumentSelector = filter,
                     DiagnosticKinds = [VSInternalDiagnosticKind.Syntax]
                 }
             }];

src/Razor/src/Microsoft.VisualStudio.LanguageServices.Razor/LanguageClient/Cohost/CohostDocumentSpellCheckEndpoint.cs

@@ -31,7 +31,7 @@ internal sealed class CohostDocumentSpellCheckEndpoint(
 
     protected override bool RequiresLSPSolution => true;
 
-    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, DocumentFilter[] filter, RazorCohostRequestContext requestContext)
+    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, RazorCohostRequestContext requestContext)
     {
         if (clientCapabilities.SupportsVisualStudioExtensions)
         {
@@ -39,9 +39,6 @@ internal sealed class CohostDocumentSpellCheckEndpoint(
             {
                 Method = VSInternalMethods.TextDocumentSpellCheckableRangesName,
                 RegisterOptions = new TextDocumentRegistrationOptions()
-                {
-                    DocumentSelector = filter
-                }
             }];
         }
 

src/Razor/src/Microsoft.VisualStudio.LanguageServices.Razor/LanguageClient/Cohost/CohostDocumentSymbolEndpoint.cs

@@ -30,7 +30,7 @@ internal class CohostDocumentSymbolEndpoint(IRemoteServiceInvoker remoteServiceI
 
     protected override bool RequiresLSPSolution => true;
 
-    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, DocumentFilter[] filter, RazorCohostRequestContext requestContext)
+    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, RazorCohostRequestContext requestContext)
     {
         if (clientCapabilities.TextDocument?.DocumentSymbol?.DynamicRegistration == true)
         {
@@ -40,9 +40,6 @@ internal class CohostDocumentSymbolEndpoint(IRemoteServiceInvoker remoteServiceI
             {
                 Method = Methods.TextDocumentDocumentSymbolName,
                 RegisterOptions = new DocumentSymbolRegistrationOptions()
-                {
-                    DocumentSelector = filter
-                }
             }];
         }
 

src/Razor/src/Microsoft.VisualStudio.LanguageServices.Razor/LanguageClient/Cohost/CohostEndpointRegistration.cs

@@ -18,7 +18,7 @@ namespace Microsoft.VisualStudio.Razor.LanguageClient.Cohost;
 #pragma warning restore RS0030 // Do not use banned APIs
 internal sealed class CohostEndpointRegistration : IDynamicRegistrationProvider
 {
-    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, DocumentFilter[] filter, RazorCohostRequestContext requestContext)
+    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, RazorCohostRequestContext requestContext)
     {
         return [
             // Project Context, for the nav bar
@@ -26,25 +26,18 @@ internal sealed class CohostEndpointRegistration : IDynamicRegistrationProvider
             {
                 Method = VSMethods.GetProjectContextsName,
                 RegisterOptions = new TextDocumentRegistrationOptions()
-                {
-                    DocumentSelector = filter
-                }
             },
             // DidOpen, DidChange, DidClose, for document synchronization
             new Registration
             {
                 Method = Methods.TextDocumentDidOpenName,
                 RegisterOptions = new TextDocumentRegistrationOptions()
-                {
-                    DocumentSelector = filter
-                }
             },
             new Registration
             {
                 Method = Methods.TextDocumentDidChangeName,
                 RegisterOptions = new TextDocumentChangeRegistrationOptions()
                 {
-                    DocumentSelector = filter,
                     SyncKind = TextDocumentSyncKind.Incremental
                 }
             },
@@ -52,9 +45,6 @@ internal sealed class CohostEndpointRegistration : IDynamicRegistrationProvider
             {
                 Method = Methods.TextDocumentDidCloseName,
                 RegisterOptions = new TextDocumentRegistrationOptions()
-                {
-                    DocumentSelector = filter
-                }
             },
         ];
     }

src/Razor/src/Microsoft.VisualStudio.LanguageServices.Razor/LanguageClient/Cohost/CohostFoldingRangeEndpoint.cs

@@ -41,7 +41,7 @@ internal class CohostFoldingRangeEndpoint(
 
     protected override bool RequiresLSPSolution => true;
 
-    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, DocumentFilter[] filter, RazorCohostRequestContext requestContext)
+    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, RazorCohostRequestContext requestContext)
     {
         if (clientCapabilities.TextDocument?.FoldingRange?.DynamicRegistration is true)
         {
@@ -49,9 +49,6 @@ internal class CohostFoldingRangeEndpoint(
             {
                 Method = Methods.TextDocumentFoldingRangeName,
                 RegisterOptions = new FoldingRangeRegistrationOptions()
-                {
-                    DocumentSelector = filter
-                }
             }];
         }
 

src/Razor/src/Microsoft.VisualStudio.LanguageServices.Razor/LanguageClient/Cohost/CohostGoToDefinitionEndpoint.cs

@@ -45,14 +45,14 @@ internal sealed class CohostGoToDefinitionEndpoint(
 
     protected override bool RequiresLSPSolution => true;
 
-    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, DocumentFilter[] filter, RazorCohostRequestContext requestContext)
+    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, RazorCohostRequestContext requestContext)
     {
         if (clientCapabilities.TextDocument?.Definition?.DynamicRegistration == true)
         {
             return [new Registration
             {
                 Method = Methods.TextDocumentDefinitionName,
-                RegisterOptions = new DefinitionOptions()
+                RegisterOptions = new DefinitionRegistrationOptions()
             }];
         }
 

src/Razor/src/Microsoft.VisualStudio.LanguageServices.Razor/LanguageClient/Cohost/CohostGoToImplementationEndpoint.cs

@@ -41,14 +41,14 @@ internal sealed class CohostGoToImplementationEndpoint(
 
     protected override bool RequiresLSPSolution => true;
 
-    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, DocumentFilter[] filter, RazorCohostRequestContext requestContext)
+    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, RazorCohostRequestContext requestContext)
     {
         if (clientCapabilities.TextDocument?.Implementation?.DynamicRegistration == true)
         {
             return [new Registration
             {
                 Method = Methods.TextDocumentImplementationName,
-                RegisterOptions = new ImplementationOptions()
+                RegisterOptions = new ImplementationRegistrationOptions()
             }];
         }
 

src/Razor/src/Microsoft.VisualStudio.LanguageServices.Razor/LanguageClient/Cohost/CohostHoverEndpoint.cs

@@ -0,0 +1,119 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the MIT license. See License.txt in the project root for license information.
+
+using System.Collections.Immutable;
+using System.Composition;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Razor;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.ExternalAccess.Razor.Cohost;
+using Microsoft.CodeAnalysis.Razor.Remote;
+using Microsoft.VisualStudio.LanguageServer.ContainedLanguage;
+using Microsoft.VisualStudio.LanguageServer.Protocol;
+using RoslynHover = Roslyn.LanguageServer.Protocol.Hover;
+using RoslynLspFactory = Roslyn.LanguageServer.Protocol.RoslynLspFactory;
+using VsHover = Microsoft.VisualStudio.LanguageServer.Protocol.Hover;
+
+namespace Microsoft.VisualStudio.Razor.LanguageClient.Cohost;
+
+#pragma warning disable RS0030 // Do not use banned APIs
+[Shared]
+[CohostEndpoint(Methods.TextDocumentHoverName)]
+[Export(typeof(IDynamicRegistrationProvider))]
+[ExportCohostStatelessLspService(typeof(CohostHoverEndpoint))]
+[method: ImportingConstructor]
+#pragma warning restore RS0030 // Do not use banned APIs
+internal sealed class CohostHoverEndpoint(
+    IRemoteServiceInvoker remoteServiceInvoker,
+    IHtmlDocumentSynchronizer htmlDocumentSynchronizer,
+    LSPRequestInvoker requestInvoker)
+    : AbstractRazorCohostDocumentRequestHandler<TextDocumentPositionParams, SumType<RoslynHover, VsHover>?>, IDynamicRegistrationProvider
+{
+    private readonly IRemoteServiceInvoker _remoteServiceInvoker = remoteServiceInvoker;
+    private readonly IHtmlDocumentSynchronizer _htmlDocumentSynchronizer = htmlDocumentSynchronizer;
+    private readonly LSPRequestInvoker _requestInvoker = requestInvoker;
+
+    protected override bool MutatesSolutionState => false;
+
+    protected override bool RequiresLSPSolution => true;
+
+    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, RazorCohostRequestContext requestContext)
+    {
+        if (clientCapabilities.TextDocument?.Hover?.DynamicRegistration == true)
+        {
+            return [new Registration
+            {
+                Method = Methods.TextDocumentHoverName,
+                RegisterOptions = new HoverRegistrationOptions()
+            }];
+        }
+
+        return [];
+    }
+
+    protected override RazorTextDocumentIdentifier? GetRazorTextDocumentIdentifier(TextDocumentPositionParams request)
+        => request.TextDocument.ToRazorTextDocumentIdentifier();
+
+    protected override Task<SumType<RoslynHover, VsHover>?> HandleRequestAsync(TextDocumentPositionParams request, RazorCohostRequestContext context, CancellationToken cancellationToken)
+        => HandleRequestAsync(
+            request,
+            context.TextDocument.AssumeNotNull(),
+            cancellationToken);
+
+    private async Task<SumType<RoslynHover, VsHover>?> HandleRequestAsync(TextDocumentPositionParams request, TextDocument razorDocument, CancellationToken cancellationToken)
+    {
+        var position = RoslynLspFactory.CreatePosition(request.Position.ToLinePosition());
+
+        var response = await _remoteServiceInvoker
+            .TryInvokeAsync<IRemoteHoverService, RemoteResponse<RoslynHover?>>(
+                razorDocument.Project.Solution,
+                (service, solutionInfo, cancellationToken) =>
+                    service.GetHoverAsync(solutionInfo, razorDocument.Id, position, cancellationToken),
+                cancellationToken)
+            .ConfigureAwait(false);
+
+        if (response.Result is RoslynHover hover)
+        {
+            return hover;
+        }
+
+        if (response.StopHandling)
+        {
+            return null;
+        }
+
+        return await GetHtmlHoverAsync(request, razorDocument, cancellationToken).ConfigureAwait(false);
+    }
+
+    private async Task<VsHover?> GetHtmlHoverAsync(TextDocumentPositionParams request, TextDocument razorDocument, CancellationToken cancellationToken)
+    {
+        var htmlDocument = await _htmlDocumentSynchronizer.TryGetSynchronizedHtmlDocumentAsync(razorDocument, cancellationToken).ConfigureAwait(false);
+        if (htmlDocument is null)
+        {
+            return null;
+        }
+
+        request.TextDocument = request.TextDocument.WithUri(htmlDocument.Uri);
+
+        var result = await _requestInvoker
+            .ReinvokeRequestOnServerAsync<TextDocumentPositionParams, VsHover?>(
+                htmlDocument.Buffer,
+                Methods.TextDocumentHoverName,
+                RazorLSPConstants.HtmlLanguageServerName,
+                request,
+                cancellationToken)
+            .ConfigureAwait(false);
+
+        return result?.Response;
+    }
+
+    internal TestAccessor GetTestAccessor() => new(this);
+
+    internal readonly struct TestAccessor(CohostHoverEndpoint instance)
+    {
+        public Task<SumType<RoslynHover, VsHover>?> HandleRequestAsync(
+            TextDocumentPositionParams request, TextDocument razorDocument, CancellationToken cancellationToken)
+            => instance.HandleRequestAsync(request, razorDocument, cancellationToken);
+    }
+}

src/Razor/src/Microsoft.VisualStudio.LanguageServices.Razor/LanguageClient/Cohost/CohostInlayHintEndpoint.cs

@@ -30,7 +30,7 @@ internal class CohostInlayHintEndpoint(IRemoteServiceInvoker remoteServiceInvoke
 
     protected override bool RequiresLSPSolution => true;
 
-    public ImmutableArray<VSLSP.Registration> GetRegistrations(VSLSP.VSInternalClientCapabilities clientCapabilities, VSLSP.DocumentFilter[] filter, RazorCohostRequestContext requestContext)
+    public ImmutableArray<VSLSP.Registration> GetRegistrations(VSLSP.VSInternalClientCapabilities clientCapabilities, RazorCohostRequestContext requestContext)
     {
         if (clientCapabilities.TextDocument?.InlayHint?.DynamicRegistration == true)
         {
@@ -38,9 +38,6 @@ internal class CohostInlayHintEndpoint(IRemoteServiceInvoker remoteServiceInvoke
             {
                 Method = Methods.TextDocumentInlayHintName,
                 RegisterOptions = new VSLSP.InlayHintRegistrationOptions()
-                {
-                    DocumentSelector = filter
-                }
             }];
         }
 

src/Razor/src/Microsoft.VisualStudio.LanguageServices.Razor/LanguageClient/Cohost/CohostLinkedEditingRangeEndpoint.cs

@@ -32,7 +32,7 @@ internal class CohostLinkedEditingRangeEndpoint(IRemoteServiceInvoker remoteServ
 
     protected override bool RequiresLSPSolution => true;
 
-    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, DocumentFilter[] filter, RazorCohostRequestContext requestContext)
+    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, RazorCohostRequestContext requestContext)
     {
         if (clientCapabilities.TextDocument?.LinkedEditingRange?.DynamicRegistration == true)
         {
@@ -40,9 +40,6 @@ internal class CohostLinkedEditingRangeEndpoint(IRemoteServiceInvoker remoteServ
             {
                 Method = Methods.TextDocumentLinkedEditingRangeName,
                 RegisterOptions = new LinkedEditingRangeRegistrationOptions()
-                {
-                    DocumentSelector = filter
-                }
             }];
         }
 

src/Razor/src/Microsoft.VisualStudio.LanguageServices.Razor/LanguageClient/Cohost/CohostOnAutoInsertEndpoint.cs

@@ -67,14 +67,14 @@ internal class CohostOnAutoInsertEndpoint(
 
     protected override bool RequiresLSPSolution => true;
 
-    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, DocumentFilter[] filter, RazorCohostRequestContext requestContext)
+    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, RazorCohostRequestContext requestContext)
     {
         if (clientCapabilities.SupportsVisualStudioExtensions)
         {
             return [new Registration
             {
                 Method = VSInternalMethods.OnAutoInsertName,
-                RegisterOptions = new VSInternalDocumentOnAutoInsertOptions()
+                RegisterOptions = new VSInternalDocumentOnAutoInsertRegistrationOptions()
                     .EnableOnAutoInsert(_triggerCharacters)
             }];
         }

src/Razor/src/Microsoft.VisualStudio.LanguageServices.Razor/LanguageClient/Cohost/CohostOnTypeFormattingEndpoint.cs

@@ -46,7 +46,7 @@ internal sealed class CohostOnTypeFormattingEndpoint(
 
     protected override bool RequiresLSPSolution => true;
 
-    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, DocumentFilter[] filter, RazorCohostRequestContext requestContext)
+    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, RazorCohostRequestContext requestContext)
     {
         if (clientCapabilities.TextDocument?.Formatting?.DynamicRegistration is true)
         {
@@ -54,9 +54,7 @@ internal sealed class CohostOnTypeFormattingEndpoint(
             {
                 Method = Methods.TextDocumentOnTypeFormattingName,
                 RegisterOptions = new DocumentOnTypeFormattingRegistrationOptions()
-                {
-                    DocumentSelector = filter,
-                }.EnableOnTypeFormattingTriggerCharacters()
+                    .EnableOnTypeFormattingTriggerCharacters()
             }];
         }
 

src/Razor/src/Microsoft.VisualStudio.LanguageServices.Razor/LanguageClient/Cohost/CohostRangeFormattingEndpoint.cs

@@ -45,7 +45,7 @@ internal sealed class CohostRangeFormattingEndpoint(
 
     protected override bool RequiresLSPSolution => true;
 
-    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, DocumentFilter[] filter, RazorCohostRequestContext requestContext)
+    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, RazorCohostRequestContext requestContext)
     {
         if (clientCapabilities.TextDocument?.Formatting?.DynamicRegistration is true)
         {
@@ -53,9 +53,6 @@ internal sealed class CohostRangeFormattingEndpoint(
             {
                 Method = Methods.TextDocumentRangeFormattingName,
                 RegisterOptions = new DocumentRangeFormattingRegistrationOptions()
-                {
-                    DocumentSelector = filter
-                }
             }];
         }
 

src/Razor/src/Microsoft.VisualStudio.LanguageServices.Razor/LanguageClient/Cohost/CohostRenameEndpoint.cs

@@ -35,7 +35,7 @@ internal class CohostRenameEndpoint(
 
     protected override bool RequiresLSPSolution => true;
 
-    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, DocumentFilter[] filter, RazorCohostRequestContext requestContext)
+    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, RazorCohostRequestContext requestContext)
     {
         if (clientCapabilities.TextDocument?.Rename?.DynamicRegistration == true)
         {
@@ -44,7 +44,6 @@ internal class CohostRenameEndpoint(
                 Method = Methods.TextDocumentRenameName,
                 RegisterOptions = new RenameRegistrationOptions()
                 {
-                    DocumentSelector = filter,
                     PrepareProvider = false
                 }
             }];

src/Razor/src/Microsoft.VisualStudio.LanguageServices.Razor/LanguageClient/Cohost/CohostSemanticTokensRangeEndpoint.cs

@@ -43,7 +43,7 @@ internal sealed class CohostSemanticTokensRangeEndpoint(
     protected override bool MutatesSolutionState => false;
     protected override bool RequiresLSPSolution => true;
 
-    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, DocumentFilter[] filter, RazorCohostRequestContext requestContext)
+    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, RazorCohostRequestContext requestContext)
     {
         if (clientCapabilities.TextDocument?.SemanticTokens?.DynamicRegistration == true)
         {
@@ -55,9 +55,7 @@ internal sealed class CohostSemanticTokensRangeEndpoint(
             {
                 Method = Methods.TextDocumentSemanticTokensRangeName,
                 RegisterOptions = new SemanticTokensRegistrationOptions()
-                {
-                    DocumentSelector = filter,
-                }.EnableSemanticTokens(_semanticTokensLegendService)
+                    .EnableSemanticTokens(_semanticTokensLegendService)
             }];
         }
 

src/Razor/src/Microsoft.VisualStudio.LanguageServices.Razor/LanguageClient/Cohost/CohostSignatureHelpEndpoint.cs

@@ -46,7 +46,7 @@ internal class CohostSignatureHelpEndpoint(
 
     protected override bool RequiresLSPSolution => true;
 
-    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, DocumentFilter[] filter, RazorCohostRequestContext requestContext)
+    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, RazorCohostRequestContext requestContext)
     {
         if (clientCapabilities.TextDocument?.SignatureHelp?.DynamicRegistration == true)
         {
@@ -54,9 +54,7 @@ internal class CohostSignatureHelpEndpoint(
             {
                 Method = Methods.TextDocumentSignatureHelpName,
                 RegisterOptions = new SignatureHelpRegistrationOptions()
-                {
-                    DocumentSelector = filter
-                }.EnableSignatureHelp()
+                    .EnableSignatureHelp()
             }];
         }
 

src/Razor/src/Microsoft.VisualStudio.LanguageServices.Razor/LanguageClient/Cohost/CohostTextPresentationEndpoint.cs

@@ -35,7 +35,7 @@ internal class CohostTextPresentationEndpoint(
 
     protected override bool RequiresLSPSolution => true;
 
-    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, DocumentFilter[] filter, RazorCohostRequestContext requestContext)
+    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, RazorCohostRequestContext requestContext)
     {
         if (clientCapabilities.SupportsVisualStudioExtensions)
         {
@@ -43,9 +43,6 @@ internal class CohostTextPresentationEndpoint(
             {
                 Method = VSInternalMethods.TextDocumentTextPresentationName,
                 RegisterOptions = new TextDocumentRegistrationOptions()
-                {
-                    DocumentSelector = filter
-                }
             }];
         }
 

src/Razor/src/Microsoft.VisualStudio.LanguageServices.Razor/LanguageClient/Cohost/CohostUriPresentationEndpoint.cs

@@ -39,7 +39,7 @@ internal class CohostUriPresentationEndpoint(
 
     protected override bool RequiresLSPSolution => true;
 
-    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, DocumentFilter[] filter, RazorCohostRequestContext requestContext)
+    public ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, RazorCohostRequestContext requestContext)
     {
         if (clientCapabilities.SupportsVisualStudioExtensions)
         {
@@ -47,9 +47,6 @@ internal class CohostUriPresentationEndpoint(
             {
                 Method = VSInternalMethods.TextDocumentUriPresentationName,
                 RegisterOptions = new TextDocumentRegistrationOptions()
-                {
-                    DocumentSelector = filter
-                }
             }];
         }
 

src/Razor/src/Microsoft.VisualStudio.LanguageServices.Razor/LanguageClient/Cohost/IDynamicRegistrationProvider.cs

@@ -9,5 +9,5 @@ namespace Microsoft.VisualStudio.Razor.LanguageClient.Cohost;
 
 internal interface IDynamicRegistrationProvider
 {
-    ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, DocumentFilter[] filter, RazorCohostRequestContext requestContext);
+    ImmutableArray<Registration> GetRegistrations(VSInternalClientCapabilities clientCapabilities, RazorCohostRequestContext requestContext);
 }

src/Razor/src/Microsoft.VisualStudio.LanguageServices.Razor/LanguageClient/Cohost/RazorCohostDynamicRegistrationService.cs

@@ -23,7 +23,7 @@ internal class RazorCohostDynamicRegistrationService(
     Lazy<RazorCohostClientCapabilitiesService> lazyRazorCohostClientCapabilitiesService)
     : IRazorCohostDynamicRegistrationService
 {
-    private readonly DocumentFilter[] _filter = [new DocumentFilter()
+    private static readonly DocumentFilter[] s_filter = [new DocumentFilter()
     {
         Language = Constants.RazorLanguageName,
         Pattern = "**/*.{razor,cshtml}"
@@ -50,10 +50,15 @@ internal class RazorCohostDynamicRegistrationService(
 
         foreach (var provider in _lazyRegistrationProviders)
         {
-            foreach (var registration in provider.Value.GetRegistrations(clientCapabilities, _filter, requestContext))
+            foreach (var registration in provider.Value.GetRegistrations(clientCapabilities, requestContext))
             {
                 // We don't unregister anything, so we don't need to do anything interesting with Ids
                 registration.Id = Guid.NewGuid().ToString();
+                if (registration.RegisterOptions is ITextDocumentRegistrationOptions options)
+                {
+                    options.DocumentSelector = s_filter;
+                }
+
                 registrations.Add(registration);
             }
         }

src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostEndpointTest.cs

@@ -0,0 +1,186 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the MIT license. See License.txt in the project root for license information.
+
+using System;
+using System.Collections.Generic;
+using System.ComponentModel.Composition;
+using System.Linq;
+using System.Reflection;
+using System.Threading;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Razor.Test.Common;
+using Microsoft.AspNetCore.Razor.Test.Common.Mef;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.ExternalAccess.Razor.Cohost;
+using Microsoft.CodeAnalysis.Razor.Workspaces;
+using Microsoft.VisualStudio.LanguageServer.Client;
+using Microsoft.VisualStudio.LanguageServer.ContainedLanguage;
+using Microsoft.VisualStudio.LanguageServer.Protocol;
+using Microsoft.VisualStudio.Razor;
+using Microsoft.VisualStudio.Razor.LanguageClient.Cohost;
+using Microsoft.VisualStudio.Text;
+using Microsoft.VisualStudio.Threading;
+using Newtonsoft.Json.Linq;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace Microsoft.VisualStudio.LanguageServices.Razor.Test.Cohost;
+
+public class CohostEndpointTest(ITestOutputHelper testOutputHelper) : ToolingTestBase(testOutputHelper)
+{
+    [Fact]
+    public void EndpointsHaveUniqueLSPMethods()
+    {
+        var methods = new Dictionary<string, Type>();
+
+        var endpoints = typeof(CohostColorPresentationEndpoint).Assembly.GetTypes()
+            .Where(t => t.GetCustomAttribute<CohostEndpointAttribute>() != null)
+            .Select(t => (t, t.GetCustomAttribute<CohostEndpointAttribute>().Method));
+
+        foreach (var (endpointType, method) in endpoints)
+        {
+            if (methods.TryGetValue(method, out var existing))
+            {
+                Assert.Fail($"Could not register {endpointType.Name} for {method} because {existing.Name} already has.");
+            }
+
+            methods.Add(method, endpointType);
+        }
+    }
+
+    [Fact]
+    public void RegistrationsProvideFilter()
+    {
+        var testComposition = TestComposition.Roslyn
+            .Add(TestComposition.Editor)
+            .AddAssemblies(typeof(CohostLinkedEditingRangeEndpoint).Assembly)
+            .AddAssemblies(typeof(DefaultLSPRequestInvoker).Assembly)
+            .AddAssemblies(typeof(LanguageServerFeatureOptions).Assembly)
+            .AddParts(typeof(TestILanguageServiceBroker2))
+            .AddExcludedPartTypes(typeof(IWorkspaceProvider))
+            .AddParts(typeof(TestWorkspaceProvider))
+            .AddExcludedPartTypes(typeof(ILspEditorFeatureDetector))
+            .AddParts(typeof(TestLspEditorFeatureDetector));
+
+        using var exportProvider = testComposition.ExportProviderFactory.CreateExportProvider();
+
+        var providers = exportProvider.GetExportedValues<IDynamicRegistrationProvider>().ToList();
+
+        // First we verify that the MEF composition above is correct, otherwise this test will be invalid
+        var actualProviders = typeof(CohostLinkedEditingRangeEndpoint).Assembly.GetTypes().Where(t => !t.IsInterface && typeof(IDynamicRegistrationProvider).IsAssignableFrom(t)).ToList();
+        Assert.Equal(actualProviders.OrderBy(a => a.Name).Select(r => r.Name).ToArray(), providers.OrderBy(e => e.GetType().Name).Select(r => r.GetType().Name).ToArray());
+
+        var clientCapabilities = new VSInternalClientCapabilities()
+        {
+            SupportsVisualStudioExtensions = true,
+            TextDocument = new TextDocumentClientCapabilities()
+            {
+                CodeAction = new() { DynamicRegistration = true },
+                CodeLens = new() { DynamicRegistration = true },
+                Completion = new() { DynamicRegistration = true },
+                Definition = new() { DynamicRegistration = true },
+                Diagnostic = new() { DynamicRegistration = true },
+                DocumentHighlight = new() { DynamicRegistration = true },
+                DocumentLink = new() { DynamicRegistration = true },
+                DocumentSymbol = new() { DynamicRegistration = true },
+                FoldingRange = new() { DynamicRegistration = true },
+                Formatting = new() { DynamicRegistration = true },
+                Hover = new() { DynamicRegistration = true },
+                Implementation = new() { DynamicRegistration = true },
+                InlayHint = new() { DynamicRegistration = true },
+                LinkedEditingRange = new() { DynamicRegistration = true },
+                OnTypeFormatting = new() { DynamicRegistration = true },
+                RangeFormatting = new() { DynamicRegistration = true },
+                References = new() { DynamicRegistration = true },
+                Rename = new() { DynamicRegistration = true },
+                SemanticTokens = new() { DynamicRegistration = true },
+                SignatureHelp = new() { DynamicRegistration = true },
+                Synchronization = new() { DynamicRegistration = true },
+                TypeDefinition = new() { DynamicRegistration = true }
+            },
+        };
+
+        foreach (var endpoint in providers)
+        {
+            if (endpoint is CohostSemanticTokensRangeEndpoint)
+            {
+                // We can't currently test this, as the GetRegistrations method calls requestContext.GetRequiredService
+                // and we can't create a request context ourselves
+                continue;
+            }
+
+            var registrations = endpoint.GetRegistrations(clientCapabilities, requestContext: new());
+
+            // If we didn't get any registrations then the test is probably invalid, and we need to update client capabilities above
+            if (registrations.Length == 0)
+            {
+                Assert.Fail($"Did not get any registrations from {endpoint.GetType().Name}. Client capabilities might be wrong?");
+            }
+
+            foreach (var registration in registrations)
+            {
+                var options = registration.RegisterOptions as ITextDocumentRegistrationOptions;
+                if (options is null)
+                {
+                    Assert.Fail($"Could not convert registration options from {endpoint.GetType().Name} to {nameof(ITextDocumentRegistrationOptions)}. It was {registration.RegisterOptions?.GetType().Name}");
+                }
+            }
+        }
+    }
+
+    [Export(typeof(ILanguageServiceBroker2))]
+    private class TestILanguageServiceBroker2 : ILanguageServiceBroker2
+    {
+        public IEnumerable<ILanguageClientInstance> ActiveLanguageClients => throw new NotImplementedException();
+        public IEnumerable<Lazy<ILanguageClient, IContentTypeMetadata>> FactoryLanguageClients => throw new NotImplementedException();
+        public IEnumerable<Lazy<ILanguageClient, IContentTypeMetadata>> LanguageClients => throw new NotImplementedException();
+
+        public event EventHandler<LanguageClientLoadedEventArgs> LanguageClientLoaded { add { } remove { } }
+        public event AsyncEventHandler<LanguageClientNotifyEventArgs> ClientNotifyAsync { add { } remove { } }
+
+        public void AddCustomBufferContentTypes(IEnumerable<string> contentTypes) => throw new NotImplementedException();
+        public void AddLanguageClients(IEnumerable<Lazy<ILanguageClient, IContentTypeMetadata>> items) => throw new NotImplementedException();
+        public Task LoadAsync(IContentTypeMetadata contentType, ILanguageClient client) => throw new NotImplementedException();
+        public void Notify<T>(Notification<T> notification, CancellationToken cancellationToken) => throw new NotImplementedException();
+        public Task NotifyAsync(ILanguageClient languageClient, string method, JToken parameters, CancellationToken cancellationToken) => throw new NotImplementedException();
+        public Task OnDidChangeTextDocumentAsync(ITextSnapshot before, ITextSnapshot after, IEnumerable<ITextChange> textChanges) => throw new NotImplementedException();
+        public Task OnDidCloseTextDocumentAsync(ITextSnapshot snapShot) => throw new NotImplementedException();
+        public Task OnDidOpenTextDocumentAsync(ITextSnapshot snapShot) => throw new NotImplementedException();
+        public Task OnDidSaveTextDocumentAsync(ITextDocument document) => throw new NotImplementedException();
+        public void RemoveCustomBufferContentTypes(IEnumerable<string> contentTypes) => throw new NotImplementedException();
+        public void RemoveLanguageClients(IEnumerable<Lazy<ILanguageClient, IContentTypeMetadata>> items) => throw new NotImplementedException();
+        public IAsyncEnumerable<(string client, TResponse? response)> RequestAllAsync<TRequest, TResponse>(Request<TRequest, TResponse> request, CancellationToken cancellationToken) => throw new NotImplementedException();
+        public Task<(ILanguageClient?, JToken?)> RequestAsync(string[] contentTypes, Func<JToken, bool> capabilitiesFilter, string method, JToken parameters, CancellationToken cancellationToken) => throw new NotImplementedException();
+        public Task<(ILanguageClient?, JToken?)> RequestAsync(string[] contentTypes, Func<JToken, bool> capabilitiesFilter, string clientName, string method, JToken parameters, CancellationToken cancellationToken) => throw new NotImplementedException();
+        public Task<ManualInvocationResponse?> RequestAsync(ITextBuffer textBuffer, Func<JToken, bool> capabilitiesFilter, string languageServerName, string method, Func<ITextSnapshot, JToken> parameterFactory, CancellationToken cancellationToken) => throw new NotImplementedException();
+        public Task<JToken?> RequestAsync(ILanguageClient languageClient, string method, JToken parameters, CancellationToken cancellationToken) => throw new NotImplementedException();
+        public Task<TResponse?> RequestAsync<TRequest, TResponse>(Request<TRequest, TResponse> request, CancellationToken cancellationToken) => throw new NotImplementedException();
+        public Task<(ILanguageClient?, TOut)> RequestAsync<TIn, TOut>(string[] contentTypes, Func<ServerCapabilities, bool> capabilitiesFilter, LspRequest<TIn, TOut> method, TIn parameters, CancellationToken cancellationToken) => throw new NotImplementedException();
+        public Task<TOut> RequestAsync<TIn, TOut>(ILanguageClient languageClient, LspRequest<TIn, TOut> method, TIn parameters, CancellationToken cancellationToken) => throw new NotImplementedException();
+        public Task<IEnumerable<(ILanguageClient, JToken?)>> RequestMultipleAsync(string[] contentTypes, Func<JToken, bool> capabilitiesFilter, string method, JToken parameters, CancellationToken cancellationToken) => throw new NotImplementedException();
+        public IAsyncEnumerable<ManualInvocationResponse> RequestMultipleAsync(ITextBuffer textBuffer, Func<JToken, bool> capabilitiesFilter, string method, Func<ITextSnapshot, JToken> parameterFactory, CancellationToken cancellationToken) => throw new NotImplementedException();
+        public Task<IEnumerable<(ILanguageClient, TOut)>> RequestMultipleAsync<TIn, TOut>(string[] contentTypes, Func<ServerCapabilities, bool> capabilitiesFilter, LspRequest<TIn, TOut> method, TIn parameters, CancellationToken cancellationToken) => throw new NotImplementedException();
+    }
+
+    [Export(typeof(IWorkspaceProvider))]
+    private class TestWorkspaceProvider : IWorkspaceProvider
+    {
+        public CodeAnalysis.Workspace GetWorkspace() => throw new NotImplementedException();
+    }
+
+    [Export(typeof(ILspEditorFeatureDetector))]
+    private class TestLspEditorFeatureDetector : ILspEditorFeatureDetector
+    {
+        public bool IsLiveShareHost() => throw new NotImplementedException();
+        public bool IsLspEditorEnabled() => throw new NotImplementedException();
+        public bool IsLspEditorSupported(string documentFilePath) => throw new NotImplementedException();
+        public bool IsRemoteClient() => throw new NotImplementedException();
+    }
+
+    [Export(typeof(IRazorSemanticTokensRefreshQueue))]
+    private class TestRazorSemanticTokensRefreshQueue : IRazorSemanticTokensRefreshQueue
+    {
+        public void Initialize(string clientCapabilitiesString) => throw new NotImplementedException();
+        public Task TryEnqueueRefreshComputationAsync(Project project, CancellationToken cancellationToken) => throw new NotImplementedException();
+    }
+}

src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/CohostHoverEndpointTest.cs

@@ -0,0 +1,148 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the MIT license. See License.txt in the project root for license information.
+
+using System;
+using System.Threading.Tasks;
+using Microsoft.AspNetCore.Razor.Test.Common;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.ExternalAccess.Razor;
+using Microsoft.CodeAnalysis.Text;
+using Microsoft.VisualStudio.LanguageServer.Protocol;
+using Xunit;
+using Xunit.Abstractions;
+using RoslynHover = Roslyn.LanguageServer.Protocol.Hover;
+
+namespace Microsoft.VisualStudio.Razor.LanguageClient.Cohost;
+
+using static HoverAssertions;
+
+public class CohostHoverEndpointTest(ITestOutputHelper testOutputHelper) : CohostEndpointTestBase(testOutputHelper)
+{
+    [Fact]
+    public async Task Razor()
+    {
+        TestCode code = """
+            <[|PageTi$$tle|]></PageTitle>
+            <div></div>
+            
+            @{
+                var myVariable = "Hello";
+            
+                var length = myVariable.Length;
+            }
+            """;
+
+        await VerifyHoverAsync(code, async (hover, document) =>
+        {
+            await hover.VerifyRangeAsync(code.Span, document);
+
+            hover.VerifyRawContent(
+                Container(
+                    Container(
+                        Image,
+                        ClassifiedText(
+                            Text("Microsoft"),
+                            Punctuation("."),
+                            Text("AspNetCore"),
+                            Punctuation("."),
+                            Text("Components"),
+                            Punctuation("."),
+                            Text("Web"),
+                            Punctuation("."),
+                            Type("PageTitle")))));
+        });
+    }
+
+    [Fact]
+    public async Task Html()
+    {
+        TestCode code = """
+            <PageTitle></PageTitle>
+            <div$$></div>
+            
+            @{
+                var myVariable = "Hello";
+            
+                var length = myVariable.Length;
+            }
+            """;
+
+        var htmlResponse = new VSInternalHover();
+
+        await VerifyHoverAsync(code, htmlResponse, h => Assert.Same(htmlResponse, h));
+    }
+
+    [Fact]
+    public async Task CSharp()
+    {
+        TestCode code = """
+            <PageTitle></PageTitle>
+            <div></div>
+
+            @{
+                var $$[|myVariable|] = "Hello";
+
+                var length = myVariable.Length;
+            }
+            """;
+
+        await VerifyHoverAsync(code, async (hover, document) =>
+        {
+            await hover.VerifyRangeAsync(code.Span, document);
+
+            hover.VerifyRawContent(
+                Container(
+                    Container(
+                        Image,
+                        ClassifiedText(
+                            Punctuation("("),
+                            Text("local variable"),
+                            Punctuation(")"),
+                            WhiteSpace(" "),
+                            Keyword("string"),
+                            WhiteSpace(" "),
+                            LocalName("myVariable")))));
+        });
+    }
+
+    private async Task VerifyHoverAsync(TestCode input, Func<RoslynHover, TextDocument, Task> verifyHover)
+    {
+        var document = await CreateProjectAndRazorDocumentAsync(input.Text);
+        var result = await GetHoverResultAsync(document, input);
+
+        Assert.NotNull(result);
+        var value = result.GetValueOrDefault();
+
+        Assert.True(value.TryGetFirst(out var hover));
+        await verifyHover(hover, document);
+    }
+
+    private async Task VerifyHoverAsync(TestCode input, Hover htmlResponse, Action<Hover?> verifyHover)
+    {
+        var document = await CreateProjectAndRazorDocumentAsync(input.Text);
+        var result = await GetHoverResultAsync(document, input, htmlResponse);
+
+        Assert.NotNull(result);
+        var value = result.GetValueOrDefault();
+
+        Assert.True(value.TryGetSecond(out var hover));
+        verifyHover(hover);
+    }
+
+    private async Task<SumType<RoslynHover, Hover>?> GetHoverResultAsync(TextDocument document, TestCode input, Hover? htmlResponse = null)
+    {
+        var inputText = await document.GetTextAsync(DisposalToken);
+        var linePosition = inputText.GetLinePosition(input.Position);
+
+        var requestInvoker = new TestLSPRequestInvoker([(Methods.TextDocumentHoverName, htmlResponse)]);
+        var endpoint = new CohostHoverEndpoint(RemoteServiceInvoker, TestHtmlDocumentSynchronizer.Instance, requestInvoker);
+
+        var textDocumentPositionParams = new TextDocumentPositionParams
+        {
+            Position = VsLspFactory.CreatePosition(linePosition),
+            TextDocument = new TextDocumentIdentifier { Uri = document.CreateUri() },
+        };
+
+        return await endpoint.GetTestAccessor().HandleRequestAsync(textDocumentPositionParams, document, DisposalToken);
+    }
+}

src/Razor/test/Microsoft.VisualStudio.LanguageServices.Razor.Test/Cohost/HoverAssertions.cs

@@ -0,0 +1,99 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the MIT license. See License.txt in the project root for license information.
+
+using System;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+using System.Linq;
+using System.Threading.Tasks;
+using Microsoft.CodeAnalysis;
+using Microsoft.CodeAnalysis.Classification;
+using Microsoft.CodeAnalysis.Razor.Tooltip;
+using Microsoft.CodeAnalysis.Text;
+using Roslyn.LanguageServer.Protocol;
+using Roslyn.Text.Adornments;
+using Xunit;
+
+namespace Microsoft.VisualStudio.Razor.LanguageClient.Cohost;
+
+internal static class HoverAssertions
+{
+    public static async Task VerifyRangeAsync(this Hover hover, TextSpan expected, TextDocument document)
+    {
+        var text = await document.GetTextAsync();
+        Assert.NotNull(hover.Range);
+        Assert.Equal(text.GetLinePositionSpan(expected), hover.Range.ToLinePositionSpan());
+    }
+
+    public static void VerifyRawContent(this Hover hover, Action<object?> verifier)
+    {
+        var vsHover = Assert.IsType<VSInternalHover>(hover);
+        verifier(vsHover.RawContent);
+    }
+
+    public static Action<object?> Container(params ImmutableArray<Action<object?>> elements)
+        => o =>
+        {
+            Assert.NotNull(o);
+            var container = Assert.IsType<ContainerElement>(o);
+
+            var allElements = container.Elements.ToArray();
+            Assert.Equal(elements.Length, allElements.Length);
+
+            for (var i = 0; i < elements.Length; i++)
+            {
+                elements[i](allElements[i]);
+            }
+        };
+
+    public static Action<object?> Image
+        => o =>
+        {
+            Assert.NotNull(o);
+            Assert.IsType<ImageElement>(o);
+        };
+
+    public static Action<object?> ClassifiedText(params ImmutableArray<Action<ClassifiedTextRun>> runs)
+        => o =>
+        {
+            Assert.NotNull(o);
+            var classifiedText = Assert.IsType<ClassifiedTextElement>(o);
+
+            var allRuns = classifiedText.Runs.ToArray();
+            Assert.Equal(runs.Length, allRuns.Length);
+
+            for (var i = 0; i < runs.Length; i++)
+            {
+                runs[i](allRuns[i]);
+            }
+        };
+
+    public static Action<ClassifiedTextRun> Run(string text, string? classificationTypeName = null)
+        => run =>
+        {
+            if (classificationTypeName is not null)
+            {
+                Assert.Equal(classificationTypeName, run.ClassificationTypeName);
+            }
+
+            Assert.Equal(text, run.Text);
+        };
+
+    public static Action<ClassifiedTextRun> Keyword(string text)
+        => Run(text, ClassificationTypeNames.Keyword);
+
+    public static Action<ClassifiedTextRun> LocalName(string text)
+        => Run(text, ClassificationTypeNames.LocalName);
+
+    public static Action<ClassifiedTextRun> Punctuation(string text)
+        => Run(text, ClassificationTypeNames.Punctuation);
+
+    public static Action<ClassifiedTextRun> Text(string text)
+        => Run(text, ClassificationTypeNames.Text);
+
+    public static Action<ClassifiedTextRun> Type(string text)
+        => Run(text, ClassifiedTagHelperTooltipFactory.TypeClassificationName);
+
+    public static Action<ClassifiedTextRun> WhiteSpace(string text)
+        => Run(text, ClassificationTypeNames.WhiteSpace);
+}

src/Shared/Microsoft.AspNetCore.Razor.Utilities.Shared/Assumed.cs

@@ -40,22 +40,37 @@ internal static class Assumed
     public static void Unreachable([CallerFilePath] string? path = null, [CallerLineNumber] int line = 0)
         => ThrowInvalidOperation(SR.This_program_location_is_thought_to_be_unreachable, path, line);
 
+    /// <summary>
+    ///  Can be called at points that are assumed to be unreachable at runtime.
+    /// </summary>
+    /// <exception cref="InvalidOperationException"/>
+    [DoesNotReturn]
+    public static void Unreachable(string message, [CallerFilePath] string? path = null, [CallerLineNumber] int line = 0)
+        => ThrowInvalidOperation(message, path, line);
+
     /// <summary>
     ///  Can be called at points that are assumed to be unreachable at runtime.
     /// </summary>
     /// <exception cref="InvalidOperationException"/>
     [DoesNotReturn]
     public static T Unreachable<T>([CallerFilePath] string? path = null, [CallerLineNumber] int line = 0)
-    {
-        ThrowInvalidOperation(SR.This_program_location_is_thought_to_be_unreachable, path, line);
-        return default;
-    }
+        => ThrowInvalidOperation<T>(SR.This_program_location_is_thought_to_be_unreachable, path, line);
+
+    /// <summary>
+    ///  Can be called at points that are assumed to be unreachable at runtime.
+    /// </summary>
+    /// <exception cref="InvalidOperationException"/>
+    [DoesNotReturn]
+    public static T Unreachable<T>(string message, [CallerFilePath] string? path = null, [CallerLineNumber] int line = 0)
+        => ThrowInvalidOperation<T>(message, path, line);
 
     [DebuggerHidden]
     [DoesNotReturn]
-    [MethodImpl(MethodImplOptions.NoInlining)]
     private static void ThrowInvalidOperation(string message, string? path, int line)
-    {
-        throw new InvalidOperationException(message);
-    }
+        => ThrowHelper.ThrowInvalidOperationException(message + Environment.NewLine + SR.FormatFile_0_Line_1(path, line));
+
+    [DebuggerHidden]
+    [DoesNotReturn]
+    private static T ThrowInvalidOperation<T>(string message, string? path, int line)
+        => ThrowHelper.ThrowInvalidOperationException<T>(message + Environment.NewLine + SR.FormatFile_0_Line_1(path, line));
 }