Merged PR 785975: Probing unset mount should not cause graph (engine) cache miss

Probing unset mount should not cause graph (engine) cache miss

Related work items: #2180048

Public/Src/Engine/Dll/InputTracker.cs

@@ -837,7 +837,7 @@ namespace BuildXL.Engine
         }
 
         [SuppressMessage("Microsoft.Naming", "CA2204:Literals should be spelled correctly", MessageId = "ms")]
-        private static MatchResult? MatchesReader(
+        internal static MatchResult? MatchesReader(
             LoggingContext loggingContext,
             BinaryReader reader,
             FileContentTable fileContentTable,
@@ -921,7 +921,7 @@ namespace BuildXL.Engine
                 {
                     if (previousValue != UnsetVariableMarker)
                     {
-                        // The previously consumed environment variable is not known and was not previously unset.
+                        // The previously consumed environment variable is set with a value.
                         result.MissType = GraphCacheMissReason.EnvironmentVariableChanged;
                         result.FirstMissIdentifier = string.Format(CultureInfo.InvariantCulture, Strings.InputTracker_EnvironmentVariableRemoved, key);
                         Logger.Log.InputTrackerDetectedEnvironmentVariableChanged(loggingContext, key, previousValue, UnsetVariableMarker);
@@ -958,11 +958,14 @@ namespace BuildXL.Engine
                 }
                 else
                 {
-                    // The previously used mount is not known
-                    result.MissType = GraphCacheMissReason.MountChanged;
-                    result.FirstMissIdentifier = string.Format(CultureInfo.InvariantCulture, Strings.InputTracker_MountRemoved, mountName, previousPath);
-                    Logger.Log.InputTrackerDetectedMountChanged(loggingContext, mountName, previousPath, string.Empty);
-                    return result;
+                    if (!string.IsNullOrEmpty(previousPath))
+                    {
+                        // The previously used mount is known to have a path.
+                        result.MissType = GraphCacheMissReason.MountChanged;
+                        result.FirstMissIdentifier = string.Format(CultureInfo.InvariantCulture, Strings.InputTracker_MountRemoved, mountName, previousPath);
+                        Logger.Log.InputTrackerDetectedMountChanged(loggingContext, mountName, previousPath, string.Empty);
+                        return result;
+                    }
                 }
             }
 

Public/Src/Engine/UnitTests/Engine/InputTrackerTests.cs

@@ -0,0 +1,150 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using System.Collections.Generic;
+using System.IO;
+using System.Text;
+using BuildXL.Engine;
+using BuildXL.Storage;
+using BuildXL.Utilities.Configuration;
+using BuildXL.Utilities.Configuration.Mutable;
+using BuildXL.Utilities.Core;
+using BuildXL.Utilities.Instrumentation.Common;
+using Test.BuildXL.TestUtilities.Xunit;
+using Xunit;
+using Xunit.Abstractions;
+
+namespace Test.BuildXL.Engine
+{
+    [TestClassIfSupported(requiresWindowsBasedOperatingSystem: true)]
+    public class InputTrackerTests : TemporaryStorageTestBase
+    {
+        public InputTrackerTests(ITestOutputHelper output)
+            : base(output)
+        {
+        }
+
+        [Fact]
+        public void TestProbeUnsetEnvVar()
+        {
+            var loggingContext = new LoggingContext("Test");
+            BuildXLContext buildXLContext = BuildXLContext.CreateInstanceForTesting();
+            string fileTrackerPath = GetFullPath("fileTracker");
+            FileContentTable fileContentTable = FileContentTable.CreateStub(loggingContext);
+            var graphFingerprint = new GraphFingerprint(CompositeGraphFingerprint.Zero, CompositeGraphFingerprint.Zero);
+
+            InputTracker inputTracker = InputTracker.Create(
+                loggingContext,
+                fileContentTable,
+                JournalState.DisabledJournal,
+                graphFingerprint.ExactFingerprint);
+
+            using var stream = new MemoryStream();
+
+            using (var writer = new BinaryWriter(stream, Encoding.UTF8, leaveOpen: true))
+            {
+                inputTracker.WriteToFile(
+                    writer,
+                    buildXLContext.PathTable,
+                    new Dictionary<string, string>(1)
+                    {
+                        { "UnsetEnvVar", null } // Unset environment variable that got probed.
+                    },
+                    new Dictionary<string, IMount>(0),
+                    fileTrackerPath);
+            }
+
+            stream.Position = 0;
+            using (var reader = new BinaryReader(stream, Encoding.UTF8))
+            {
+                var configuration = new CommandLineConfiguration()
+                {
+                    Startup = new StartupConfiguration()
+                    {
+                        ConfigFile = AbsolutePath.Create(buildXLContext.PathTable, Path.Combine(TemporaryDirectory, "config.dc"))
+                    }
+                };
+                BuildXLEngine.PopulateLoggingAndLayoutConfiguration(configuration, buildXLContext.PathTable, bxlExeLocation: null, inTestMode: true);
+                MountsTable mountsTable = MountsTable.CreateAndRegister(loggingContext, buildXLContext, configuration, new Dictionary<string, string>(0));
+                mountsTable.CompleteInitialization();
+                InputTracker.MatchResult? matchResult = InputTracker.MatchesReader(
+                    loggingContext,
+                    reader,
+                    fileContentTable,
+                    JournalState.DisabledJournal,
+                    default,
+                    fileTrackerPath,
+                    BuildParameters.GetFactory().PopulateFromDictionary([]),
+                    mountsTable,
+                    graphFingerprint,
+                    1,
+                    configuration,
+                    true);
+
+                XAssert.IsTrue(matchResult.HasValue);
+                XAssert.IsTrue(matchResult.Value.Matches, $"Match result: {matchResult.Value.MissType}");
+            }
+        }
+
+        [Fact]
+        public void TestProbeUnknownMount()
+        {
+            var loggingContext = new LoggingContext("Test");
+            BuildXLContext buildXLContext = BuildXLContext.CreateInstanceForTesting();
+            string fileTrackerPath = GetFullPath("fileTracker");
+            FileContentTable fileContentTable = FileContentTable.CreateStub(loggingContext);
+            var graphFingerprint = new GraphFingerprint(CompositeGraphFingerprint.Zero, CompositeGraphFingerprint.Zero);
+
+            InputTracker inputTracker = InputTracker.Create(
+                loggingContext,
+                fileContentTable,
+                JournalState.DisabledJournal,
+                graphFingerprint.ExactFingerprint);
+
+            using var stream = new MemoryStream();
+            using (var writer = new BinaryWriter(stream, Encoding.UTF8, leaveOpen: true))
+            {
+                inputTracker.WriteToFile(
+                    writer,
+                    buildXLContext.PathTable,
+                    new Dictionary<string, string>(0),
+                    new Dictionary<string, IMount>(1)
+                    {
+                        { "UnknownMount", null } // Unknown mount that got probed.
+                    },
+                    fileTrackerPath);
+            }
+
+            stream.Position = 0;
+            using (var reader = new BinaryReader(stream, Encoding.UTF8))
+            {
+                var configuration = new CommandLineConfiguration()
+                {
+                    Startup = new StartupConfiguration()
+                    {
+                        ConfigFile = AbsolutePath.Create(buildXLContext.PathTable, Path.Combine(TemporaryDirectory, "config.dc"))
+                    }
+                };
+                BuildXLEngine.PopulateLoggingAndLayoutConfiguration(configuration, buildXLContext.PathTable, bxlExeLocation: null, inTestMode: true);
+                MountsTable mountsTable = MountsTable.CreateAndRegister(loggingContext, buildXLContext, configuration, new Dictionary<string, string>(0));
+                mountsTable.CompleteInitialization();
+                InputTracker.MatchResult? matchResult = InputTracker.MatchesReader(
+                    loggingContext,
+                    reader,
+                    fileContentTable,
+                    JournalState.DisabledJournal,
+                    default,
+                    fileTrackerPath,
+                    BuildParameters.GetFactory().PopulateFromDictionary([]),
+                    mountsTable,
+                    graphFingerprint,
+                    1,
+                    configuration,
+                    true);
+
+                XAssert.IsTrue(matchResult.HasValue);
+                XAssert.IsTrue(matchResult.Value.Matches, $"Match result: {matchResult.Value.MissType}");
+            }
+        }
+    }
+}

Public/Src/Utilities/UnitTests/Utilities/AbsolutePathTests.cs

@@ -104,6 +104,9 @@ namespace Test.BuildXL.Utilities
             XAssert.IsFalse(AbsolutePath.TryCreate(pt, @"C:\foo\bar\filename:stream", out AbsolutePath _));
             XAssert.IsFalse(AbsolutePath.TryCreate(pt, @"C:\foo\bar\filename:stream:$DATA", out AbsolutePath _));
             XAssert.IsFalse(AbsolutePath.TryCreate(pt, @"C:\foo\bar\filename::$DATA", out AbsolutePath _));
+
+            // Try create an empty path.
+            XAssert.IsFalse(AbsolutePath.TryCreate(pt, string.Empty, out AbsolutePath _));
         }
 
         [Fact]