Use the new SwiftPM API to load the build plan

We previously skipped building/running tool plugins here, which meant
that the compiler arguments for a target also missed any generated
sources. Use the new `BuildDescription.load` API from SwiftPM to address
this.

Resolves rdar://102242345.

Author: bnbarham

Sources/BuildSystemIntegration/SwiftPMBuildSystem.swift

@@ -33,15 +33,15 @@ package import BuildServerProtocol
 package import Foundation
 package import LanguageServerProtocol
 package import SKOptions
-package import SourceKitLSPAPI
+@preconcurrency package import SourceKitLSPAPI
 package import ToolchainRegistry
 package import class ToolchainRegistry.Toolchain
 #else
 import BuildServerProtocol
 import Foundation
 import LanguageServerProtocol
 import SKOptions
-import SourceKitLSPAPI
+@preconcurrency import SourceKitLSPAPI
 import ToolchainRegistry
 import class ToolchainRegistry.Toolchain
 #endif
@@ -131,6 +131,8 @@ package actor SwiftPMBuildSystem: BuiltInBuildSystem {
   private let toolchain: Toolchain
   private let swiftPMWorkspace: Workspace
 
+  private let pluginConfiguration: PluginConfiguration
+
   /// A `ObservabilitySystem` from `SwiftPM` that logs.
   private let observabilitySystem: ObservabilitySystem
 
@@ -291,6 +293,19 @@ package actor SwiftPMBuildSystem: BuiltInBuildSystem {
       prepareForIndexing: options.backgroundPreparationModeOrDefault.toSwiftPMPreparation
     )
 
+    let pluginScriptRunner = DefaultPluginScriptRunner(
+      fileSystem: localFileSystem,
+      cacheDir: location.pluginWorkingDirectory.appending("cache"),
+      toolchain: hostSwiftPMToolchain,
+      extraPluginSwiftCFlags: [],
+      enableSandbox: !(options.swiftPMOrDefault.disableSandbox ?? false)
+    )
+    self.pluginConfiguration = PluginConfiguration(
+      scriptRunner: pluginScriptRunner,
+      workDirectory: location.pluginWorkingDirectory,
+      disableSandbox: options.swiftPMOrDefault.disableSandbox ?? false
+    )
+
     packageLoadingQueue.async {
       await orLog("Initial package loading") {
         // Schedule an initial generation of the build graph. Once the build graph is loaded, the build system will send
@@ -326,27 +341,30 @@ package actor SwiftPMBuildSystem: BuiltInBuildSystem {
       }
     }
 
-    let modulesGraph = try await self.swiftPMWorkspace.loadPackageGraph(
-      rootInput: PackageGraphRootInput(packages: [AbsolutePath(validating: projectRoot.filePath)]),
-      forceResolvedVersions: !isForIndexBuild,
-      observabilityScope: observabilitySystem.topScope.makeChildScope(description: "Load package graph")
-    )
-
-    signposter.emitEvent("Finished loading modules graph", id: signpostID)
-
-    let plan = try await BuildPlan(
+    nonisolated(unsafe) let packageLoader = {
+      return try await self.swiftPMWorkspace.loadPackageGraph(
+        rootInput: PackageGraphRootInput(packages: [try AbsolutePath(validating: self.projectRoot.filePath)]),
+        forceResolvedVersions: !self.isForIndexBuild,
+        observabilityScope: self.observabilitySystem.topScope.makeChildScope(description: "Load package graph")
+      )
+    }
+    let loaded = try await BuildDescription.load(
+      location: swiftPMWorkspace.location,
       destinationBuildParameters: destinationBuildParameters,
       toolsBuildParameters: toolsBuildParameters,
-      graph: modulesGraph,
+      packageGraphLoader: packageLoader,
+      pluginConfiguration: pluginConfiguration,
       disableSandbox: options.swiftPMOrDefault.disableSandbox ?? false,
       fileSystem: localFileSystem,
-      observabilityScope: observabilitySystem.topScope.makeChildScope(description: "Create SwiftPM build plan")
+      observabilityScope: observabilitySystem.topScope.makeChildScope(description: "Create SwiftPM build description")
     )
+    if !loaded.errors.isEmpty {
+      logger.error("Loading SwiftPM description had errors: \(loaded.errors)")
+    }
 
-    signposter.emitEvent("Finished generating build plan", id: signpostID)
+    self.buildDescription = loaded.description
 
-    let buildDescription = BuildDescription(buildPlan: plan)
-    self.buildDescription = buildDescription
+    signposter.emitEvent("Finished generating build description", id: signpostID)
 
     /// Make sure to execute any throwing statements before setting any
     /// properties because otherwise we might end up in an inconsistent state
@@ -355,7 +373,7 @@ package actor SwiftPMBuildSystem: BuiltInBuildSystem {
     self.swiftPMTargets = [:]
     self.targetDependencies = [:]
 
-    buildDescription.traverseModules { buildTarget, parent in
+    loaded.description.traverseModules { buildTarget, parent in
       let targetIdentifier = orLog("Getting build target identifier") { try BuildTargetIdentifier(buildTarget) }
       guard let targetIdentifier else {
         return

Tests/SourceKitLSPTests/SwiftPMIntegrationTests.swift

@@ -359,4 +359,74 @@ final class SwiftPMIntegrationTests: XCTestCase {
       ["Cannot convert value of type 'Int' to specified type 'String'"]
     )
   }
+
+  func testToolPlugin() async throws {
+    let project = try await SwiftPMTestProject(
+      files: [
+        "Plugins/plugin.swift": #"""
+        import PackagePlugin
+        @main struct CodeGeneratorPlugin: BuildToolPlugin {
+          func createBuildCommands(context: PluginContext, target: Target) throws -> [Command] {
+            let genSourcesDir = context.pluginWorkDirectoryURL.appending(path: "GeneratedSources")
+            guard let target = target as? SourceModuleTarget else { return [] }
+            let codeGenerator = try context.tool(named: "CodeGenerator").url
+            let generatedFile = genSourcesDir.appending(path: "\(target.name)-generated.swift")
+            return [.buildCommand(
+              displayName: "Generating code for \(target.name)",
+              executable: codeGenerator,
+              arguments: [
+                generatedFile.path
+              ],
+              inputFiles: [],
+              outputFiles: [generatedFile]
+            )]
+          }
+        }
+        """#,
+
+        "Sources/CodeGenerator/CodeGenerator.swift": #"""
+        import Foundation
+        try "let generated = 1".write(to: URL(fileURLWithPath: CommandLine.arguments[1]), atomically: true, encoding: String.Encoding.utf8)
+        """#,
+
+        "Sources/TestLib/TestLib.swift": #"""
+        func useGenerated() {
+          _ = 2️⃣generated
+        }
+        """#,
+      ],
+      manifest: """
+        // swift-tools-version: 6.0
+        import PackageDescription
+        let package = Package(
+          name: "PluginTest",
+          targets: [
+            .executableTarget(name: "CodeGenerator"),
+            .target(
+              name: "TestLib",
+              plugins: [.plugin(name: "CodeGeneratorPlugin")]
+            ),
+            .plugin(
+              name: "CodeGeneratorPlugin",
+              capability: .buildTool(),
+              dependencies: ["CodeGenerator"]
+            ),
+          ]
+        )
+        """,
+      enableBackgroundIndexing: true
+    )
+
+    let (uri, positions) = try project.openDocument("TestLib.swift")
+
+    try await project.testClient.send(PollIndexRequest())
+
+    let result = try await project.testClient.send(
+      DefinitionRequest(textDocument: TextDocumentIdentifier(uri), position: positions["2️⃣"])
+    )
+    let location = try XCTUnwrap(result?.locations?.only)
+    XCTAssertTrue(location.uri.pseudoPath.hasSuffix("generated.swift"))
+    XCTAssertEqual(location.range.lowerBound, Position(line: 0, utf16index: 4))
+    XCTAssertEqual(location.range.upperBound, Position(line: 0, utf16index: 4))
+  }
 }