[Dependency Scanning] Adapt to upcoming dependency scanner API changes with the output path.

swiftlang/swift#60882 adds functionality to the Clang scan-deps invocation that produces placeholder paths as '<replace-me>'s in the generated command-line.
The first step to adapting to these changes is to teach the driver to substitute the expected file paths.

Once the scanner changes land, we will revisit the driver specifying these paths in favour of having the scanning action being able to determine the correct output location from the get-go.

Author: artemcm

Sources/SwiftDriver/ExplicitModuleBuilds/ExplicitDependencyBuildPlanner.swift

@@ -145,6 +145,9 @@ public typealias ExternalTargetModuleDetailsMap = [ModuleDependencyId: ExternalT
       // First, take the command line options provided in the dependency information
       let moduleDetails = try dependencyGraph.swiftModuleDetails(of: moduleId)
       moduleDetails.commandLine?.forEach { commandLine.appendFlags($0) }
+      // Prohibit implicit module loading
+      commandLine.appendFlags("-disable-implicit-swift-modules",
+                              "-Xcc", "-Xclang", "-Xcc", "-fno-implicit-module-maps")
 
       // Resolve all dependency module inputs for this Swift module
       try resolveExplicitModuleDependencies(moduleId: moduleId, pcmArgs: pcmArgs,
@@ -224,7 +227,9 @@ public typealias ExternalTargetModuleDetailsMap = [ModuleDependencyId: ExternalT
         // First, take the command line options provided in the dependency information
         let moduleDetails = try dependencyGraph.clangModuleDetails(of: moduleId)
         moduleDetails.commandLine.forEach { commandLine.appendFlags($0) }
-
+        // Prohibit implicit module loading
+        commandLine.appendFlags("-Xcc", "-Xclang", "-Xcc", "-fno-implicit-module-maps")
+        
         // Add the `-target` option as inherited from the dependent Swift module's PCM args
         pcmArgs.forEach { commandLine.appendFlags($0) }
 
@@ -242,6 +247,12 @@ public typealias ExternalTargetModuleDetailsMap = [ModuleDependencyId: ExternalT
         outputs.append(TypedVirtualPath(file: targetEncodedModulePath, type: .pcm))
         commandLine.appendFlags("-emit-pcm", "-module-name", moduleId.moduleName,
                                 "-o", targetEncodedModulePath.description)
+        commandLine.appendFlag("-direct-clang-cc1-module-build")
+
+        // Fixup "-o -Xcc -Xclang -Xcc '<replace-me>'"
+        if let outputIndex = commandLine.firstIndex(of: .flag("<replace-me>")) {
+          commandLine[outputIndex] = .path(VirtualPath.lookup(targetEncodedModulePath))
+        }
 
         // The only required input is the .modulemap for this module.
         // Command line options in the dependency scanner output will include the
@@ -268,9 +279,6 @@ public typealias ExternalTargetModuleDetailsMap = [ModuleDependencyId: ExternalT
   private mutating func resolveExplicitModuleDependencies(moduleId: ModuleDependencyId, pcmArgs: [String],
                                                           inputs: inout [TypedVirtualPath],
                                                           commandLine: inout [Job.ArgTemplate]) throws {
-    // Prohibit the frontend from implicitly building textual modules into binary modules.
-    commandLine.appendFlags("-disable-implicit-swift-modules", "-Xcc", "-Xclang", "-Xcc",
-                            "-fno-implicit-modules", "-Xcc", "-Xclang", "-Xcc", "-fno-implicit-module-maps")
     var swiftDependencyArtifacts: [SwiftModuleArtifactInfo] = []
     var clangDependencyArtifacts: [ClangModuleArtifactInfo] = []
     try addModuleDependencies(moduleId: moduleId, pcmArgs: pcmArgs,
@@ -298,11 +306,17 @@ public typealias ExternalTargetModuleDetailsMap = [ModuleDependencyId: ExternalT
       let clangModulePath =
         TypedVirtualPath(file: moduleArtifactInfo.modulePath.path,
                          type: .pcm)
+      // If an existing dependency module path stub exists, replace it.
+      if let existingIndex = commandLine.firstIndex(of: .flag("-fmodule-file=" + moduleArtifactInfo.moduleName + "=<replace-me>")) {
+        commandLine[existingIndex] = .flag("-fmodule-file=\(moduleArtifactInfo.moduleName)=\(clangModulePath.file.description)")
+      } else {
+        commandLine.appendFlags("-Xcc", "-Xclang", "-Xcc",
+                                "-fmodule-file=\(moduleArtifactInfo.moduleName)=\(clangModulePath.file.description)")
+      }
+      
       let clangModuleMapPath =
         TypedVirtualPath(file: moduleArtifactInfo.moduleMapPath.path,
                          type: .clangModuleMap)
-      commandLine.appendFlags("-Xcc", "-Xclang", "-Xcc",
-                              "-fmodule-file=\(moduleArtifactInfo.moduleName)=\(clangModulePath.file.description)")
       commandLine.appendFlags("-Xcc", "-Xclang", "-Xcc",
                               "-fmodule-map-file=\(clangModuleMapPath.file.description)")
       inputs.append(clangModulePath)

Tests/SwiftDriverTests/ExplicitModuleBuildTests.swift

@@ -223,6 +223,24 @@ final class ExplicitModuleBuildTests: XCTestCase {
     }
   }
 
+  func testClangModuleOutputFixups() throws {
+      do {
+        var driver = try Driver(args: ["swiftc", "-explicit-module-build",
+                                       "-module-name", "testClangModuleOutputFixups",
+                                       "test.swift"])
+        let moduleDependencyGraph =
+        try JSONDecoder().decode(
+          InterModuleDependencyGraph.self,
+          from: ModuleDependenciesInputs.fastDependencyScannerOutput.data(using: .utf8)!)
+        driver.explicitDependencyBuildPlanner =
+        try ExplicitDependencyBuildPlanner(dependencyGraph: moduleDependencyGraph,
+                                           toolchain: driver.toolchain)
+        let modulePrebuildJobs = try driver.explicitDependencyBuildPlanner!.generateExplicitModuleDependenciesBuildJobs()
+        let c_simdJob = try XCTUnwrap(modulePrebuildJobs.first(where: { $0.descriptionForLifecycle == "Compiling Clang module c_simd" }))
+        XCTAssertFalse(c_simdJob.commandLine.contains(.flag("<replace-me>")))
+      }
+  }
+
   func testModuleDependencyBuildCommandGenerationWithExternalFramework() throws {
     do {
       let externalDetails: ExternalTargetModuleDetailsMap =

Tests/SwiftDriverTests/Inputs/ExplicitModuleDependencyBuildInputs.swift

@@ -67,7 +67,9 @@ enum ModuleDependenciesInputs {
                 "-remove-preceeding-explicit-module-build-incompatible-options",
                 "-fno-implicit-modules",
                 "-emit-module",
-                "-fmodule-name=c_simd"
+                "-fmodule-name=c_simd",
+                "-o",
+                "<replace-me>"
               ]
             }
           }