Add extension methods to auto-reload a configuration on file change

Configuration.sln

@@ -1,4 +1,3 @@
-
 Microsoft Visual Studio Solution File, Format Version 12.00
 # Visual Studio 14
 VisualStudioVersion = 14.0.23107.0
@@ -45,6 +44,10 @@ Project("{8BB2217D-0F2D-49D1-97BC-3654ED321F3B}") = "Microsoft.Extensions.Config
 EndProject
 Project("{8BB2217D-0F2D-49D1-97BC-3654ED321F3B}") = "Microsoft.Extensions.Configuration.FileExtensions.Test", "test\Microsoft.Extensions.Configuration.FileExtensions.Test\Microsoft.Extensions.Configuration.FileExtensions.Test.xproj", "{F7932F19-EB68-4C52-9CD1-3B51E48C2337}"
 EndProject
+Project("{8BB2217D-0F2D-49D1-97BC-3654ED321F3B}") = "Microsoft.Extensions.Configuration.FileProviderExtensions", "src\Microsoft.Extensions.Configuration.FileProviderExtensions\Microsoft.Extensions.Configuration.FileProviderExtensions.xproj", "{5BCFD3A8-B031-4831-9BC4-4A1733F63059}"
+EndProject
+Project("{8BB2217D-0F2D-49D1-97BC-3654ED321F3B}") = "Microsoft.Extensions.Configuration.FileProviderExtensions.Test", "test\Microsoft.Extensions.Configuration.FileProviderExtensions.Test\Microsoft.Extensions.Configuration.FileProviderExtensions.Test.xproj", "{CC96A8D9-7524-4658-8653-8CAB9AD5839C}"
+EndProject
 Global
 	GlobalSection(SolutionConfigurationPlatforms) = preSolution
 		Debug|Any CPU = Debug|Any CPU
@@ -269,6 +272,30 @@ Global
 		{F7932F19-EB68-4C52-9CD1-3B51E48C2337}.Release|Mixed Platforms.Build.0 = Release|Any CPU
 		{F7932F19-EB68-4C52-9CD1-3B51E48C2337}.Release|x86.ActiveCfg = Release|Any CPU
 		{F7932F19-EB68-4C52-9CD1-3B51E48C2337}.Release|x86.Build.0 = Release|Any CPU
+		{5BCFD3A8-B031-4831-9BC4-4A1733F63059}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{5BCFD3A8-B031-4831-9BC4-4A1733F63059}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{5BCFD3A8-B031-4831-9BC4-4A1733F63059}.Debug|Mixed Platforms.ActiveCfg = Debug|Any CPU
+		{5BCFD3A8-B031-4831-9BC4-4A1733F63059}.Debug|Mixed Platforms.Build.0 = Debug|Any CPU
+		{5BCFD3A8-B031-4831-9BC4-4A1733F63059}.Debug|x86.ActiveCfg = Debug|Any CPU
+		{5BCFD3A8-B031-4831-9BC4-4A1733F63059}.Debug|x86.Build.0 = Debug|Any CPU
+		{5BCFD3A8-B031-4831-9BC4-4A1733F63059}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{5BCFD3A8-B031-4831-9BC4-4A1733F63059}.Release|Any CPU.Build.0 = Release|Any CPU
+		{5BCFD3A8-B031-4831-9BC4-4A1733F63059}.Release|Mixed Platforms.ActiveCfg = Release|Any CPU
+		{5BCFD3A8-B031-4831-9BC4-4A1733F63059}.Release|Mixed Platforms.Build.0 = Release|Any CPU
+		{5BCFD3A8-B031-4831-9BC4-4A1733F63059}.Release|x86.ActiveCfg = Release|Any CPU
+		{5BCFD3A8-B031-4831-9BC4-4A1733F63059}.Release|x86.Build.0 = Release|Any CPU
+		{CC96A8D9-7524-4658-8653-8CAB9AD5839C}.Debug|Any CPU.ActiveCfg = Debug|Any CPU
+		{CC96A8D9-7524-4658-8653-8CAB9AD5839C}.Debug|Any CPU.Build.0 = Debug|Any CPU
+		{CC96A8D9-7524-4658-8653-8CAB9AD5839C}.Debug|Mixed Platforms.ActiveCfg = Debug|Any CPU
+		{CC96A8D9-7524-4658-8653-8CAB9AD5839C}.Debug|Mixed Platforms.Build.0 = Debug|Any CPU
+		{CC96A8D9-7524-4658-8653-8CAB9AD5839C}.Debug|x86.ActiveCfg = Debug|Any CPU
+		{CC96A8D9-7524-4658-8653-8CAB9AD5839C}.Debug|x86.Build.0 = Debug|Any CPU
+		{CC96A8D9-7524-4658-8653-8CAB9AD5839C}.Release|Any CPU.ActiveCfg = Release|Any CPU
+		{CC96A8D9-7524-4658-8653-8CAB9AD5839C}.Release|Any CPU.Build.0 = Release|Any CPU
+		{CC96A8D9-7524-4658-8653-8CAB9AD5839C}.Release|Mixed Platforms.ActiveCfg = Release|Any CPU
+		{CC96A8D9-7524-4658-8653-8CAB9AD5839C}.Release|Mixed Platforms.Build.0 = Release|Any CPU
+		{CC96A8D9-7524-4658-8653-8CAB9AD5839C}.Release|x86.ActiveCfg = Release|Any CPU
+		{CC96A8D9-7524-4658-8653-8CAB9AD5839C}.Release|x86.Build.0 = Release|Any CPU
 	EndGlobalSection
 	GlobalSection(SolutionProperties) = preSolution
 		HideSolutionNode = FALSE
@@ -293,5 +320,7 @@ Global
 		{AE6FFE9B-6378-4D57-AA24-7D257F18B235} = {B54371FF-B920-46C8-8D55-6B19DBB43EBF}
 		{881E7CBC-492C-47C5-98A6-61DD1C753EE6} = {F141E2D0-F9B8-4ADB-A19A-7B6FF4CA19A1}
 		{F7932F19-EB68-4C52-9CD1-3B51E48C2337} = {B54371FF-B920-46C8-8D55-6B19DBB43EBF}
+		{5BCFD3A8-B031-4831-9BC4-4A1733F63059} = {F141E2D0-F9B8-4ADB-A19A-7B6FF4CA19A1}
+		{CC96A8D9-7524-4658-8653-8CAB9AD5839C} = {B54371FF-B920-46C8-8D55-6B19DBB43EBF}
 	EndGlobalSection
 EndGlobal

src/Microsoft.Extensions.Configuration.FileExtensions/FileConfigurationExtensions.cs

@@ -2,7 +2,6 @@
 // Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
 
 using System;
-using System.IO;
 
 namespace Microsoft.Extensions.Configuration
 {

src/Microsoft.Extensions.Configuration.FileProviderExtensions/ConfigurationRootExtensions.cs

@@ -0,0 +1,92 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using Microsoft.AspNet.FileProviders;
+
+namespace Microsoft.Extensions.Configuration
+{
+    public static class FileProviderExtensions
+    {
+        public static IConfigurationRoot ReloadOnChanged(this IConfigurationRoot config, string filename)
+        {
+            if (config == null)
+            {
+                throw new ArgumentNullException(nameof(config));
+            }
+
+            if (filename == null)
+            {
+                throw new ArgumentNullException(nameof(filename));
+            }
+#if NET451
+            var basePath = AppDomain.CurrentDomain.GetData("APP_CONTEXT_BASE_DIRECTORY") as string ??
+                AppDomain.CurrentDomain.BaseDirectory ?? string.Empty;
+#else
+            var basePath = AppContext.BaseDirectory ?? string.Empty;
+#endif
+            return ReloadOnChanged(config, basePath, filename);
+        }
+
+        public static IConfigurationRoot ReloadOnChanged(
+            this IConfigurationRoot config,
+            string basePath,
+            string filename)
+        {
+            if (config == null)
+            {
+                throw new ArgumentNullException(nameof(config));
+            }
+
+            if (basePath == null)
+            {
+                throw new ArgumentNullException(nameof(basePath));
+            }
+
+            if (filename == null)
+            {
+                throw new ArgumentNullException(nameof(filename));
+            }
+
+            var fileProvider = new PhysicalFileProvider(basePath);
+            return ReloadOnChanged(config, fileProvider, filename);
+        }
+
+        public static IConfigurationRoot ReloadOnChanged(
+            this IConfigurationRoot config,
+            IFileProvider fileProvider,
+            string filename)
+        {
+            if (config == null)
+            {
+                throw new ArgumentNullException(nameof(config));
+            }
+
+            if (fileProvider == null)
+            {
+                throw new ArgumentNullException(nameof(fileProvider));
+            }
+
+            if (filename == null)
+            {
+                throw new ArgumentNullException(nameof(filename));
+            }
+
+            Action<object> callback = null;
+            callback = _ =>
+            {
+                // The order here is important. We need to take the token and then apply our changes BEFORE
+                // registering. This prevents us from possible having two change updates to process concurrently.
+                //
+                // If the file changes after we take the token, then we'll process the update immediately upon
+                // registering the callback.
+                var token = fileProvider.Watch(filename);
+                config.Reload();
+                token.RegisterChangeCallback(callback, null);
+            };
+
+            fileProvider.Watch(filename).RegisterChangeCallback(callback, null);
+            return config;
+        }
+    }
+}

src/Microsoft.Extensions.Configuration.FileProviderExtensions/Microsoft.Extensions.Configuration.FileProviderExtensions.xproj

@@ -0,0 +1,20 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="14.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <PropertyGroup>
+    <VisualStudioVersion Condition="'$(VisualStudioVersion)' == ''">14.0</VisualStudioVersion>
+    <VSToolsPath Condition="'$(VSToolsPath)' == ''">$(MSBuildExtensionsPath32)\Microsoft\VisualStudio\v$(VisualStudioVersion)</VSToolsPath>
+  </PropertyGroup>
+
+  <Import Project="$(VSToolsPath)\DNX\Microsoft.DNX.Props" Condition="'$(VSToolsPath)' != ''" />
+  <PropertyGroup Label="Globals">
+    <ProjectGuid>5bcfd3a8-b031-4831-9bc4-4a1733f63059</ProjectGuid>
+    <RootNamespace>Microsoft.Extensions.Configuration.FileProviderExtensions</RootNamespace>
+    <BaseIntermediateOutputPath Condition="'$(BaseIntermediateOutputPath)'=='' ">..\..\artifacts\obj\$(MSBuildProjectName)</BaseIntermediateOutputPath>
+    <OutputPath Condition="'$(OutputPath)'=='' ">..\..\artifacts\bin\$(MSBuildProjectName)\</OutputPath>
+  </PropertyGroup>
+
+  <PropertyGroup>
+    <SchemaVersion>2.0</SchemaVersion>
+  </PropertyGroup>
+  <Import Project="$(VSToolsPath)\DNX\Microsoft.DNX.targets" Condition="'$(VSToolsPath)' != ''" />
+</Project>

src/Microsoft.Extensions.Configuration.FileProviderExtensions/project.json

@@ -0,0 +1,18 @@
+{
+  "version": "1.0.0-*",
+  "description": "Extension methods for using configuration with file providers.",
+  "repository": {
+    "type": "git",
+    "url": "https://github.com/aspnet/configuration"
+  },
+  "dependencies": {
+    "Microsoft.AspNet.FileProviders.Physical": "1.0.0-*",
+    "Microsoft.Extensions.Configuration.Abstractions": "1.0.0-*",
+    "Microsoft.Extensions.Configuration.FileExtensions": "1.0.0-*"
+  },
+  "frameworks": {
+    "net451": { },
+    "dotnet5.4": { },
+    "netcore50": { }
+  }
+}

test/Microsoft.Extensions.Configuration.FileProviderExtensions.Test/ConfigurationRootExtensionsTest.cs

@@ -0,0 +1,107 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Collections.Generic;
+using System.Threading;
+using Microsoft.AspNet.FileProviders;
+using Microsoft.Extensions.Primitives;
+using Xunit;
+
+namespace Microsoft.Extensions.Configuration
+{
+    public class ConfigurationRootExtensionsTest
+    {
+        [Fact]
+        public void ReloadOnChanged_GetTokenBeforeReload()
+        {
+            // Arrange
+            var tokenSource1 = new CancellationTokenSource();
+            var tokenSource2 = new CancellationTokenSource();
+
+            var fileProvider = new MockFileProvider();
+            fileProvider.Cancel = tokenSource1;
+
+            var configuration = new MockConfigurationRoot();
+            configuration.OnReload = () => Assert.Equal(2, fileProvider.WatchCount);
+
+            // Act-1
+            configuration.ReloadOnChanged(fileProvider, "config.json");
+
+            // Assert-1
+            Assert.Equal(1, fileProvider.WatchCount);
+            Assert.Equal(0, configuration.ReloadCount);
+
+            // Act-2
+            fileProvider.Cancel = tokenSource2;
+            tokenSource1.Cancel();
+
+            Assert.Equal(2, fileProvider.WatchCount);
+            Assert.Equal(1, configuration.ReloadCount);
+        }
+
+        private class MockConfigurationRoot : IConfigurationRoot
+        {
+            public Action OnReload { get; set; }
+
+            public int ReloadCount { get; private set; }
+
+            public string this[string key]
+            {
+                get
+                {
+                    throw new NotImplementedException();
+                }
+
+                set
+                {
+                    throw new NotImplementedException();
+                }
+            }
+
+            public IEnumerable<IConfigurationSection> GetChildren()
+            {
+                throw new NotImplementedException();
+            }
+
+            public IChangeToken GetReloadToken()
+            {
+                throw new NotImplementedException();
+            }
+
+            public IConfigurationSection GetSection(string key)
+            {
+                throw new NotImplementedException();
+            }
+
+            public void Reload()
+            {
+                OnReload?.Invoke();
+                ReloadCount++;
+            }
+        }
+
+        private class MockFileProvider : IFileProvider
+        {
+            public CancellationTokenSource Cancel { get; set; }
+
+            public int WatchCount { get; private set; }
+
+            public IDirectoryContents GetDirectoryContents(string subpath)
+            {
+                throw new NotImplementedException();
+            }
+
+            public IFileInfo GetFileInfo(string subpath)
+            {
+                throw new NotImplementedException();
+            }
+
+            public IChangeToken Watch(string filter)
+            {
+                WatchCount++;
+                return new CancellationChangeToken(Cancel.Token);
+            }
+        }
+    }
+}

test/Microsoft.Extensions.Configuration.FileProviderExtensions.Test/Microsoft.Extensions.Configuration.FileProviderExtensions.Test.xproj

@@ -0,0 +1,21 @@
+<?xml version="1.0" encoding="utf-8"?>
+<Project ToolsVersion="14.0" DefaultTargets="Build" xmlns="http://schemas.microsoft.com/developer/msbuild/2003">
+  <PropertyGroup>
+    <VisualStudioVersion Condition="'$(VisualStudioVersion)' == ''">14.0</VisualStudioVersion>
+    <VSToolsPath Condition="'$(VSToolsPath)' == ''">$(MSBuildExtensionsPath32)\Microsoft\VisualStudio\v$(VisualStudioVersion)</VSToolsPath>
+  </PropertyGroup>
+  <Import Project="$(VSToolsPath)\DNX\Microsoft.DNX.Props" Condition="'$(VSToolsPath)' != ''" />
+  <PropertyGroup Label="Globals">
+    <ProjectGuid>cc96a8d9-7524-4658-8653-8cab9ad5839c</ProjectGuid>
+    <RootNamespace>Microsoft.Extensions.Configuration.FileProviderExtensions.Test</RootNamespace>
+    <BaseIntermediateOutputPath Condition="'$(BaseIntermediateOutputPath)'=='' ">..\..\artifacts\obj\$(MSBuildProjectName)</BaseIntermediateOutputPath>
+    <OutputPath Condition="'$(OutputPath)'=='' ">..\..\artifacts\bin\$(MSBuildProjectName)\</OutputPath>
+  </PropertyGroup>
+  <PropertyGroup>
+    <SchemaVersion>2.0</SchemaVersion>
+  </PropertyGroup>
+  <ItemGroup>
+    <Service Include="{82a7f48d-3b50-4b1e-b82e-3ada8210c358}" />
+  </ItemGroup>
+  <Import Project="$(VSToolsPath)\DNX\Microsoft.DNX.targets" Condition="'$(VSToolsPath)' != ''" />
+</Project>

test/Microsoft.Extensions.Configuration.FileProviderExtensions.Test/project.json

@@ -0,0 +1,14 @@
+{
+  "dependencies": {
+    "Microsoft.Extensions.Configuration.FileProviderExtensions": "1.0.0-*",
+    "Microsoft.Extensions.Configuration.Test.Common": "1.0.0-*",
+    "xunit.runner.aspnet": "2.0.0-aspnet-*"
+  },
+  "frameworks": {
+    "dnx451": { },
+    "dnxcore50": { }
+  },
+  "commands": {
+    "test": "xunit.runner.aspnet"
+  }
+}