feat(rust): allow specifying features to cargo metadata

docs/environment-variables.md

@@ -5,7 +5,7 @@ Environment variables are sometimes used to control experimental features or adv
 ## `DisableGoCliScan`
 
 If the environment variable `DisableGoCliScan` is set to "true", we fall back to parsing `go.mod` and `go.sum` ourselves. 
-Otherwise, the Go detector uses go-cli command: `go list -m all` to discover Go dependencies.
+Otherwise, the Go detector uses go-cli command: `go list -m all` to discover Go dependencies. [^1]
 
 ## `PyPiMaxCacheEntries`
 
@@ -18,4 +18,11 @@ When set to any value, enables detector experiments, a feature to compare the re
 same ecosystem. The available experiments are found in the [`Experiments\Config`](../src/Microsoft.ComponentDetection.Orchestrator/Experiments/Configs)
 folder.
 
-[1]: https://go.dev/ref/mod#go-mod-graph
+## `CD_RUST_CLI_FEATURES`
+
+Specifies the features (comma seperated) to be passed into `cargo metadata`, which tells cargo to build the project with
+the features for the workspace/project. By default, `cargo metadata` will run with `--all-features`, instructing `cargo`
+to determine the build graph if all features should be built in the project/workspace. [^2]
+
+[^1]: https://go.dev/ref/mod#go-mod-graph
+[^2]: https://doc.rust-lang.org/cargo/commands/cargo-metadata.html#feature-selection

src/Microsoft.ComponentDetection.Detectors/rust/RustCliDetector.cs

@@ -26,29 +26,35 @@ public class RustCliDetector : FileComponentDetector, IExperimentalDetector
         @"^(?<packageName>[^ ]+)(?: (?<version>[^ ]+))?(?: \((?<source>[^()]*)\))?$",
         RegexOptions.Compiled);
 
+    internal const string CustomFeaturesEnvironmentVariable = "CD_RUST_CLI_FEATURES";
+
     private static readonly TomlModelOptions TomlOptions = new TomlModelOptions
     {
         IgnoreMissingProperties = true,
     };
 
     private readonly ICommandLineInvocationService cliService;
+    private readonly IEnvironmentVariableService environmentVariableService;
 
     /// <summary>
     /// Initializes a new instance of the <see cref="RustCliDetector"/> class.
     /// </summary>
     /// <param name="componentStreamEnumerableFactory">The component stream enumerable factory.</param>
     /// <param name="walkerFactory">The walker factory.</param>
     /// <param name="cliService">The command line invocation service.</param>
+    /// <param name="environmentVariableService">The environment variable service.</param>
     /// <param name="logger">The logger.</param>
     public RustCliDetector(
         IComponentStreamEnumerableFactory componentStreamEnumerableFactory,
         IObservableDirectoryWalkerFactory walkerFactory,
         ICommandLineInvocationService cliService,
+        IEnvironmentVariableService environmentVariableService,
         ILogger<RustCliDetector> logger)
     {
         this.ComponentStreamEnumerableFactory = componentStreamEnumerableFactory;
         this.Scanner = walkerFactory;
         this.cliService = cliService;
+        this.environmentVariableService = environmentVariableService;
         this.Logger = logger;
     }
 
@@ -86,12 +92,15 @@ protected override async Task OnFileFoundAsync(ProcessRequest processRequest, ID
             }
             else
             {
-                // Use --all-features to ensure that even optional feature dependencies are detected.
+                // Use --all-features to ensure that even optional feature dependencies are detected if env var isnt set.
+                var specifiedFeatures =
+                    this.environmentVariableService.GetEnvironmentVariable(CustomFeaturesEnvironmentVariable);
+
                 var cliResult = await this.cliService.ExecuteCommandAsync(
                     "cargo",
                     null,
                     "metadata",
-                    "--all-features",
+                    string.IsNullOrEmpty(specifiedFeatures) ? "--all-features" : $"--features={specifiedFeatures}",
                     "--manifest-path",
                     componentStream.Location,
                     "--format-version=1",

test/Microsoft.ComponentDetection.Detectors.Tests/RustCliDetectorTests.cs

@@ -21,6 +21,7 @@ public class RustCliDetectorTests : BaseDetectorTest<RustCliDetector>
 {
     private Mock<ICommandLineInvocationService> mockCliService;
     private Mock<IComponentStreamEnumerableFactory> mockComponentStreamEnumerableFactory;
+    private Mock<IEnvironmentVariableService> mockEnvVarService;
 
     [TestInitialize]
     public void InitCliMock()
@@ -29,6 +30,8 @@ public void InitCliMock()
         this.DetectorTestUtility.AddServiceMock(this.mockCliService);
         this.mockComponentStreamEnumerableFactory = new Mock<IComponentStreamEnumerableFactory>();
         this.DetectorTestUtility.AddServiceMock(this.mockComponentStreamEnumerableFactory);
+        this.mockEnvVarService = new Mock<IEnvironmentVariableService>();
+        this.DetectorTestUtility.AddServiceMock(this.mockEnvVarService);
     }
 
     [TestMethod]
@@ -1137,4 +1140,27 @@ public async Task RustCliDetector_FallBackLogicTriggeredOnFailedProcessingAsync(
 
         return;
     }
+
+    [TestMethod]
+    public async Task RustCLiDetector_CustomFeaturesPassedIfPresentAsync()
+    {
+        this.mockCliService
+            .Setup(x => x.CanCommandBeLocatedAsync("cargo", It.IsAny<IEnumerable<string>>()))
+            .ReturnsAsync(true);
+
+        var capturedCargoArgs = Enumerable.Empty<string>();
+        this.mockCliService.Setup(x =>
+                x.ExecuteCommandAsync("cargo", It.IsAny<IEnumerable<string>>(), It.IsAny<string[]>()))
+            .Callback((string _, IEnumerable<string> _, string[] args) => capturedCargoArgs = args);
+
+        this.mockEnvVarService
+            .Setup(x => x.GetEnvironmentVariable(RustCliDetector.CustomFeaturesEnvironmentVariable))
+            .Returns("a,b");
+
+        var (scanResult, componentRecorder) = await this.DetectorTestUtility
+            .WithFile("Cargo.toml", string.Empty)
+            .ExecuteDetectorAsync();
+
+        capturedCargoArgs.Should().Contain("--features=a,b");
+    }
 }