Add DotnetSdkPredictor

src/BuildPrediction/Predictors/DotnetSdkPredictor.cs

@@ -0,0 +1,46 @@
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using System.Collections.Concurrent;
+using System.IO;
+using Microsoft.Build.Execution;
+
+namespace Microsoft.Build.Prediction.Predictors;
+
+/// <summary>
+/// Makes predictions based on using Microsoft.NET.Sdk.
+/// </summary>
+public sealed class DotnetSdkPredictor : IProjectPredictor
+{
+    internal const string UsingMicrosoftNETSdkPropertyName = "UsingMicrosoftNETSdk";
+
+    private readonly ConcurrentDictionary<string, bool> _globalJsonExistenceCache = new(PathComparer.Instance);
+
+    /// <inheritdoc/>
+    public void PredictInputsAndOutputs(
+        ProjectInstance projectInstance,
+        ProjectPredictionReporter predictionReporter)
+    {
+        var usingMicrosoftNETSdk = projectInstance.GetPropertyValue(UsingMicrosoftNETSdkPropertyName);
+        if (!usingMicrosoftNETSdk.Equals("true", StringComparison.OrdinalIgnoreCase))
+        {
+            return;
+        }
+
+        // Microsoft.NET.Sdk reads global.json.
+        string currentProbeDirectory = projectInstance.Directory;
+        while (currentProbeDirectory != null)
+        {
+            string globalJsonPath = Path.Combine(currentProbeDirectory, "global.json");
+            bool globalJsonPathExists = _globalJsonExistenceCache.GetOrAdd(globalJsonPath, File.Exists);
+            if (globalJsonPathExists)
+            {
+                predictionReporter.ReportInputFile(globalJsonPath);
+                break;
+            }
+
+            currentProbeDirectory = Path.GetDirectoryName(currentProbeDirectory);
+        }
+    }
+}

src/BuildPrediction/ProjectPredictors.cs

@@ -60,6 +60,7 @@ public static class ProjectPredictors
         /// <item><see cref="ModuleDefinitionFilePredictor"/></item>
         /// <item><see cref="CppContentFilesProjectOutputGroupPredictor"/></item>
         /// <item><see cref="LinkItemsPredictor"/></item>
+        /// <item><see cref="DotnetSdkPredictor"/></item>
         /// </list>
         /// </remarks>
         /// <returns>A collection of <see cref="IProjectPredictor"/>.</returns>
@@ -106,6 +107,7 @@ public static class ProjectPredictors
             new ModuleDefinitionFilePredictor(),
             new CppContentFilesProjectOutputGroupPredictor(),
             new LinkItemsPredictor(),
+            new DotnetSdkPredictor(),
             //// NOTE! When adding a new predictor here, be sure to update the doc comment above.
         };
 

src/BuildPredictionTests/Predictors/DotnetSdkPredictorTests.cs

@@ -0,0 +1,115 @@
+// Copyright (c) Microsoft. All rights reserved.
+// Licensed under the MIT license. See LICENSE file in the project root for full license information.
+
+using System;
+using System.IO;
+using Microsoft.Build.Construction;
+using Microsoft.Build.Execution;
+using Microsoft.Build.Prediction.Predictors;
+using Xunit;
+
+namespace Microsoft.Build.Prediction.Tests.Predictors;
+
+public class DotnetSdkPredictorTests
+{
+    private readonly string _rootDir;
+
+    public DotnetSdkPredictorTests()
+    {
+        // Isolate each test into its own folder
+        _rootDir = Path.Combine(Directory.GetCurrentDirectory(), nameof(DotnetSdkPredictorTests), Guid.NewGuid().ToString());
+        Directory.CreateDirectory(_rootDir);
+    }
+
+    [Fact]
+    public void GlobalJsonExistsAdjacent()
+    {
+        ProjectRootElement projectRootElement = ProjectRootElement.Create(Path.Combine(_rootDir, @"src\project.csproj"));
+        projectRootElement.AddProperty(DotnetSdkPredictor.UsingMicrosoftNETSdkPropertyName, "true");
+
+        Directory.CreateDirectory(Path.Combine(_rootDir, "src"));
+        File.WriteAllText(Path.Combine(_rootDir, @"src\global.json"), "{}");
+
+        // Extraneous one above, which is not predicted as an input.
+        File.WriteAllText(Path.Combine(_rootDir, "global.json"), "{}");
+
+        ProjectInstance projectInstance = TestHelpers.CreateProjectInstanceFromRootElement(projectRootElement);
+
+        var expectedInputFiles = new[]
+        {
+            new PredictedItem(@"src\global.json", nameof(DotnetSdkPredictor)),
+        };
+
+        new DotnetSdkPredictor()
+            .GetProjectPredictions(projectInstance)
+            .AssertPredictions(
+                projectInstance,
+                expectedInputFiles.MakeAbsolute(_rootDir),
+                null,
+                null,
+                null);
+    }
+
+    [Fact]
+    public void GlobalJsonExistsAbove()
+    {
+        ProjectRootElement projectRootElement = ProjectRootElement.Create(Path.Combine(_rootDir, @"src\project.csproj"));
+        projectRootElement.AddProperty(DotnetSdkPredictor.UsingMicrosoftNETSdkPropertyName, "true");
+
+        File.WriteAllText(Path.Combine(_rootDir, "global.json"), "{}");
+
+        ProjectInstance projectInstance = TestHelpers.CreateProjectInstanceFromRootElement(projectRootElement);
+
+        var expectedInputFiles = new[]
+        {
+            new PredictedItem(@"global.json", nameof(DotnetSdkPredictor)),
+        };
+
+        new DotnetSdkPredictor()
+            .GetProjectPredictions(projectInstance)
+            .AssertPredictions(
+                projectInstance,
+                expectedInputFiles.MakeAbsolute(_rootDir),
+                null,
+                null,
+                null);
+    }
+
+    [Fact]
+    public void NoGlobalJsonExists()
+    {
+        ProjectRootElement projectRootElement = ProjectRootElement.Create(Path.Combine(_rootDir, @"src\project.csproj"));
+        projectRootElement.AddProperty(DotnetSdkPredictor.UsingMicrosoftNETSdkPropertyName, "true");
+
+        ProjectInstance projectInstance = TestHelpers.CreateProjectInstanceFromRootElement(projectRootElement);
+
+        new DotnetSdkPredictor()
+            .GetProjectPredictions(projectInstance)
+            .AssertPredictions(
+                projectInstance,
+                null,
+                null,
+                null,
+                null);
+    }
+
+    [Fact]
+    public void NotUsingDotnetSdk()
+    {
+        ProjectRootElement projectRootElement = ProjectRootElement.Create(Path.Combine(_rootDir, @"src\project.csproj"));
+
+        Directory.CreateDirectory(Path.Combine(_rootDir, "src"));
+        File.WriteAllText(Path.Combine(_rootDir, "global.json"), "{}");
+
+        ProjectInstance projectInstance = TestHelpers.CreateProjectInstanceFromRootElement(projectRootElement);
+
+        new DotnetSdkPredictor()
+            .GetProjectPredictions(projectInstance)
+            .AssertPredictions(
+                projectInstance,
+                null,
+                null,
+                null,
+                null);
+    }
+}