[BridgingHeader] Support automatic bridging header chaining

Teach swift driver to handle bridging header chaining and pass the
correct arguments to swift-frontend.

Author: cachemeifyoucan

Sources/CSwiftScan/include/swiftscan_header.h

@@ -17,8 +17,8 @@
 #include <stddef.h>
 #include <stdint.h>
 
-#define SWIFTSCAN_VERSION_MAJOR 1
-#define SWIFTSCAN_VERSION_MINOR 0
+#define SWIFTSCAN_VERSION_MAJOR 2
+#define SWIFTSCAN_VERSION_MINOR 1
 
 //=== Public Scanner Data Types -------------------------------------------===//
 
@@ -143,6 +143,12 @@ typedef struct {
   (*swiftscan_swift_textual_detail_get_swift_overlay_dependencies)(swiftscan_module_details_t);
   swiftscan_string_ref_t
   (*swiftscan_swift_textual_detail_get_module_cache_key)(swiftscan_module_details_t);
+  swiftscan_string_ref_t
+  (*swiftscan_swift_textual_detail_get_user_module_version)(swiftscan_module_details_t);
+  swiftscan_string_ref_t
+  (*swiftscan_swift_textual_detail_get_chained_bridging_header_path)(swiftscan_module_details_t);
+  swiftscan_string_ref_t
+  (*swiftscan_swift_textual_detail_get_chained_bridging_header_content)(swiftscan_module_details_t);
 
   //=== Swift Binary Module Details query APIs ------------------------------===//
   swiftscan_string_ref_t

Sources/SwiftDriver/Driver/Driver.swift

@@ -332,17 +332,38 @@ public struct Driver {
     }
   }
 
+  /// If PCH job is needed.
+  let producePCHJob: Bool
+
+  /// Original ObjC Header passed from command-line
+  let originalObjCHeaderFile: VirtualPath.Handle?
+
   /// The path to the imported Objective-C header.
-  let importedObjCHeader: VirtualPath.Handle?
+  lazy var importedObjCHeader: VirtualPath.Handle? = {
+    assert(explicitDependencyBuildPlanner != nil ||
+           !parsedOptions.hasArgument(.driverExplicitModuleBuild) ||
+           !inputFiles.contains { $0.type == .swift },
+           "should not be queried before scanning")
+    let chainedBridgingHeader = try? explicitDependencyBuildPlanner?.getChainedBridgingHeaderFile()
+    return try? computeImportedObjCHeader(&parsedOptions, compilerMode: compilerMode,
+                                          chainedBridgingHeader: chainedBridgingHeader) ?? originalObjCHeaderFile
+  }()
+
+  /// The directory to emit PCH file.
+  lazy var bridgingPrecompiledHeaderOutputDir: VirtualPath? = {
+    return try? computePrecompiledBridgingHeaderDir(&parsedOptions,
+                                                    compilerMode: compilerMode)
+  }()
 
   /// The path to the pch for the imported Objective-C header.
   lazy var bridgingPrecompiledHeader: VirtualPath.Handle? = {
     let contextHash = try? explicitDependencyBuildPlanner?.getMainModuleContextHash()
-    return Self.computeBridgingPrecompiledHeader(&parsedOptions,
-                                                 compilerMode: compilerMode,
-                                                 importedObjCHeader: importedObjCHeader,
-                                                 outputFileMap: outputFileMap,
-                                                 contextHash: contextHash)
+    return computeBridgingPrecompiledHeader(&parsedOptions,
+                                            compilerMode: compilerMode,
+                                            importedObjCHeader: importedObjCHeader,
+                                            outputFileMap: outputFileMap,
+                                            outputDirectory: bridgingPrecompiledHeaderOutputDir,
+                                            contextHash: contextHash)
   }()
 
   /// Path to the dependencies file.
@@ -1049,8 +1070,6 @@ public struct Driver {
       parsedOptions: parsedOptions,
       recordedInputModificationDates: recordedInputModificationDates)
 
-    self.importedObjCHeader = try Self.computeImportedObjCHeader(&parsedOptions, compilerMode: compilerMode, diagnosticEngine: diagnosticEngine)
-
     self.supportedFrontendFlags =
       try Self.computeSupportedCompilerArgs(of: self.toolchain,
                                             libSwiftScan: self.swiftScanLibInstance,
@@ -1075,16 +1094,38 @@ public struct Driver {
         diagnosticsEngine.emit(.warning("-cache-compile-job cannot be used without explicit module build, turn off caching"),
                                location: nil)
         self.enableCaching = false
-      } else if importedObjCHeader != nil, !parsedOptions.hasFlag(positive: .enableBridgingPch, negative: .disableBridgingPch, default: true) {
-        diagnosticsEngine.emit(.warning("-cache-compile-job cannot be used with -disable-bridging-pch, turn off caching"),
-                               location: nil)
-        self.enableCaching = false
       } else {
         self.enableCaching = true
       }
     } else {
       self.enableCaching = false
     }
+
+    // PCH related options.
+    if parsedOptions.hasArgument(.importObjcHeader) {
+      // Check for conflicting options.
+      if parsedOptions.hasArgument(.importUnderlyingModule) {
+        diagnosticEngine.emit(.error_framework_bridging_header)
+      }
+
+      if parsedOptions.hasArgument(.emitModuleInterface, .emitModuleInterfacePath) {
+        diagnosticEngine.emit(.error_bridging_header_module_interface)
+      }
+    }
+    var maybeNeedPCH = parsedOptions.hasFlag(positive: .enableBridgingPch, negative: .disableBridgingPch, default: true)
+    if enableCaching && !maybeNeedPCH {
+      diagnosticsEngine.emit(.warning("-cache-compile-job cannot be used with -disable-bridging-pch, turn on PCH generation"),
+                             location: nil)
+      maybeNeedPCH = true
+    }
+    self.producePCHJob = maybeNeedPCH
+
+    if let objcHeaderPathArg = parsedOptions.getLastArgument(.importObjcHeader) {
+      self.originalObjCHeaderFile = try? VirtualPath.intern(path: objcHeaderPathArg.asSingle)
+    } else {
+      self.originalObjCHeaderFile = nil
+    }
+
     self.useClangIncludeTree = !parsedOptions.hasArgument(.noClangIncludeTree) && !env.keys.contains("SWIFT_CACHING_USE_CLANG_CAS_FS")
     self.scannerPrefixMap = try Self.computeScanningPrefixMapper(&parsedOptions)
     if let sdkMapping =  parsedOptions.getLastArgument(.scannerPrefixMapSdk)?.asSingle {
@@ -3052,36 +3093,47 @@ extension Driver {
 // Imported Objective-C header.
 extension Driver {
   /// Compute the path of the imported Objective-C header.
-  static func computeImportedObjCHeader(
+  func computeImportedObjCHeader(
     _ parsedOptions: inout ParsedOptions,
     compilerMode: CompilerMode,
-    diagnosticEngine: DiagnosticsEngine
-  ) throws -> VirtualPath.Handle? {
-    guard let objcHeaderPathArg = parsedOptions.getLastArgument(.importObjcHeader) else {
-      return nil
+    chainedBridgingHeader: ChainedBridgingHeaderFile?) throws -> VirtualPath.Handle? {
+    // handle chained bridging header.
+    if let chainedHeader = chainedBridgingHeader, !chainedHeader.path.isEmpty {
+      let path = try VirtualPath(path: chainedHeader.path)
+      let dirExists = try fileSystem.exists(path.parentDirectory)
+      if !dirExists, let dirToCreate = path.parentDirectory.absolutePath {
+        try fileSystem.createDirectory(dirToCreate, recursive: true)
+      }
+      try fileSystem.writeFileContents(path,
+                                       bytes: ByteString(encodingAsUTF8: chainedHeader.content),
+                                       atomically: true)
+      return path.intern()
     }
+    return originalObjCHeaderFile
+  }
 
-    // Check for conflicting options.
-    if parsedOptions.hasArgument(.importUnderlyingModule) {
-      diagnosticEngine.emit(.error_framework_bridging_header)
+  /// Compute the path to the bridging precompiled header directory path.
+  func computePrecompiledBridgingHeaderDir(
+    _ parsedOptions: inout ParsedOptions,
+    compilerMode: CompilerMode) throws -> VirtualPath? {
+    if let input = originalObjCHeaderFile,
+       let outputPath = try? outputFileMap?.existingOutput(inputFile: input, outputType: .pch) {
+      return VirtualPath.lookup(outputPath).parentDirectory
     }
-
-    if parsedOptions.hasArgument(.emitModuleInterface, .emitModuleInterfacePath) {
-      diagnosticEngine.emit(.error_bridging_header_module_interface)
+    if let outputDir = parsedOptions.getLastArgument(.pchOutputDir)?.asSingle {
+      return try VirtualPath(path: outputDir)
     }
-
-    return try VirtualPath.intern(path: objcHeaderPathArg.asSingle)
+    return nil
   }
 
   /// Compute the path of the generated bridging PCH for the Objective-C header.
-  static func computeBridgingPrecompiledHeader(_ parsedOptions: inout ParsedOptions,
-                                               compilerMode: CompilerMode,
-                                               importedObjCHeader: VirtualPath.Handle?,
-                                               outputFileMap: OutputFileMap?,
-                                               contextHash: String?) -> VirtualPath.Handle? {
-    guard compilerMode.supportsBridgingPCH,
-      let input = importedObjCHeader,
-      parsedOptions.hasFlag(positive: .enableBridgingPch, negative: .disableBridgingPch, default: true) else {
+  func computeBridgingPrecompiledHeader(_ parsedOptions: inout ParsedOptions,
+                                        compilerMode: CompilerMode,
+                                        importedObjCHeader: VirtualPath.Handle?,
+                                        outputFileMap: OutputFileMap?,
+                                        outputDirectory: VirtualPath?,
+                                        contextHash: String?) -> VirtualPath.Handle? {
+    guard compilerMode.supportsBridgingPCH, producePCHJob, let input = importedObjCHeader else {
         return nil
     }
 
@@ -3096,8 +3148,8 @@ extension Driver {
     } else {
       pchFile = baseName.appendingFileTypeExtension(.pch)
     }
-    if let outputDirectory = parsedOptions.getLastArgument(.pchOutputDir)?.asSingle {
-      return try? VirtualPath(path: outputDirectory).appending(component: pchFile).intern()
+    if let outputDirectory = outputDirectory {
+      return outputDirectory.appending(component: pchFile).intern()
     } else {
       return try? VirtualPath.temporary(RelativePath(validating: pchFile)).intern()
     }

Sources/SwiftDriver/ExplicitModuleBuilds/ExplicitDependencyBuildPlanner.swift

@@ -27,6 +27,12 @@ public struct ExternalTargetModuleDetails {
   let isFramework: Bool
 }
 
+/// A chained bridging header file.
+public struct ChainedBridgingHeaderFile {
+  let path: String
+  let content: String
+}
+
 public typealias ExternalTargetModuleDetailsMap = [ModuleDependencyId: ExternalTargetModuleDetails]
 
 /// In Explicit Module Build mode, this planner is responsible for generating and providing
@@ -451,6 +457,17 @@ public typealias ExternalTargetModuleDetailsMap = [ModuleDependencyId: ExternalT
     return mainModuleDetails.contextHash
   }
 
+  /// Get the chained bridging header info
+  public func getChainedBridgingHeaderFile() throws -> ChainedBridgingHeaderFile? {
+    let mainModuleId: ModuleDependencyId = .swift(dependencyGraph.mainModuleName)
+    let mainModuleDetails = try dependencyGraph.swiftModuleDetails(of: mainModuleId)
+    guard let path = mainModuleDetails.chainedBridgingHeaderPath,
+          let content = mainModuleDetails.chainedBridgingHeaderContent else{
+      return nil
+    }
+    return ChainedBridgingHeaderFile(path: path, content: content)
+  }
+
   /// Resolve all module dependencies of the main module and add them to the lists of
   /// inputs and command line flags.
   public mutating func resolveBridgingHeaderDependencies(inputs: inout [TypedVirtualPath],

Sources/SwiftDriver/ExplicitModuleBuilds/InterModuleDependencies/InterModuleDependencyGraph.swift

@@ -124,7 +124,7 @@ public struct SwiftModuleDetails: Codable, Hashable {
   /// Options to the compile command
   public var commandLine: [String]? = []
 
-  /// Options to the compile command
+  /// Options to the compile bridging header command
   public var bridgingPchCommandLine: [String]? = []
 
   /// The context hash for this module that encodes the producing interface's path,
@@ -140,6 +140,11 @@ public struct SwiftModuleDetails: Codable, Hashable {
 
   /// The module cache key of the output module.
   public var moduleCacheKey: String?
+
+  /// Chained bridging header path
+  public var chainedBridgingHeaderPath: String?
+  /// Chained bridging header content
+  public var chainedBridgingHeaderContent: String?
 }
 
 /// Details specific to Swift placeholder dependencies.

Sources/SwiftDriver/ExplicitModuleBuilds/ModuleDependencyScanning.swift

@@ -12,6 +12,7 @@
 
 import protocol TSCBasic.FileSystem
 import struct TSCBasic.AbsolutePath
+import struct TSCBasic.RelativePath
 import struct TSCBasic.Diagnostic
 import var TSCBasic.localFileSystem
 import var TSCBasic.stdoutStream
@@ -163,6 +164,34 @@ public extension Driver {
       }
     }
 
+    if isFrontendArgSupported(.autoBridgingHeaderChaining) {
+      if parsedOptions.hasFlag(positive: .autoBridgingHeaderChaining,
+                               negative: .noAutoBridgingHeaderChaining,
+                               default: false) || isCachingEnabled {
+        if producePCHJob {
+          commandLine.appendFlag(.autoBridgingHeaderChaining)
+        } else {
+          diagnosticEngine.emit(.warning("-auto-bridging-header-chaining requires generatePCH job, no chaining will be performed"))
+          commandLine.appendFlag(.noAutoBridgingHeaderChaining)
+        }
+      } else {
+        commandLine.appendFlag(.noAutoBridgingHeaderChaining)
+      }
+    }
+
+    // Provide a directory to path to scanner for where the chained bridging header will be.
+    // Prefer writing next to pch output, otherwise next to module output path before fallback to temp directory for non-caching build.
+    if isFrontendArgSupported(.scannerOutputDir) {
+      if let outputDir = try? computePrecompiledBridgingHeaderDir(&parsedOptions,
+                                                                  compilerMode: compilerMode) {
+        commandLine.appendFlag(.scannerOutputDir)
+        commandLine.appendPath(outputDir)
+      } else {
+        commandLine.appendFlag(.scannerOutputDir)
+        commandLine.appendPath(VirtualPath.temporary(try RelativePath(validating: "scanner")))
+      }
+    }
+
     // Pass on the input files
     commandLine.append(contentsOf: inputFiles.filter { $0.type == .swift }.map { .path($0.file) })
     return (inputs, commandLine)

Sources/SwiftDriver/Jobs/FrontendJobHelpers.swift

@@ -455,26 +455,39 @@ extension Driver {
       try commandLine.appendAll(.Xcc, from: &parsedOptions)
     }
 
-    if let importedObjCHeader = importedObjCHeader,
-        bridgingHeaderHandling != .ignored {
-      commandLine.appendFlag(.importObjcHeader)
-      if bridgingHeaderHandling == .precompiled,
-          let pch = bridgingPrecompiledHeader {
-        // For explicit module build, we directly pass the compiled pch as
-        // `-import-objc-header`, rather than rely on swift-frontend to locate
+    let objcHeaderFile = (kind == .scanDependencies) ? originalObjCHeaderFile : importedObjCHeader
+    if let importedObjCHeader = objcHeaderFile, bridgingHeaderHandling != .ignored {
+      if bridgingHeaderHandling == .precompiled, let pch = bridgingPrecompiledHeader {
+        // For explicit module build, we directly pass the compiled pch to
+        // swift-frontend, rather than rely on swift-frontend to locate
         // the pch in the pchOutputDir and can start an implicit build in case
         // of a lookup failure.
         if parsedOptions.contains(.pchOutputDir) &&
            !parsedOptions.contains(.driverExplicitModuleBuild) {
+          commandLine.appendFlag(.importObjcHeader)
           try addPathArgument(VirtualPath.lookup(importedObjCHeader), to:&commandLine, remap: jobNeedPathRemap)
           try commandLine.appendLast(.pchOutputDir, from: &parsedOptions)
           if !compilerMode.isSingleCompilation {
             commandLine.appendFlag(.pchDisableValidation)
           }
         } else {
-          try addPathArgument(VirtualPath.lookup(pch), to:&commandLine, remap: jobNeedPathRemap)
+          // If header chaining is enabled, pass objc header through `-import-objc-header` and
+          // PCH file through `-import-pch`. Otherwise, pass either the PCH or header through
+          // `-import-objc-header` option.
+          if isFrontendArgSupported(.importPch), importedObjCHeader != originalObjCHeaderFile {
+            commandLine.appendFlag(.importPch)
+            try addPathArgument(VirtualPath.lookup(pch), to:&commandLine, remap: jobNeedPathRemap)
+            if let originalHeader = originalObjCHeaderFile {
+              commandLine.appendFlag(.importObjcHeader)
+              try addPathArgument(VirtualPath.lookup(originalHeader), to:&commandLine, remap: jobNeedPathRemap)
+            }
+          } else {
+            commandLine.appendFlag(.importObjcHeader)
+            try addPathArgument(VirtualPath.lookup(pch), to:&commandLine, remap: jobNeedPathRemap)
+          }
         }
       } else {
+        commandLine.appendFlag(.importObjcHeader)
         try addPathArgument(VirtualPath.lookup(importedObjCHeader), to:&commandLine, remap: jobNeedPathRemap)
       }
     }
@@ -957,8 +970,7 @@ extension Driver {
       return [:]
     }
     // Resolve command-line first.
-    let resolver = try ArgsResolver(fileSystem: fileSystem)
-    let arguments: [String] = try resolver.resolveArgumentList(for: commandLine)
+    let arguments: [String] = try executor.resolver.resolveArgumentList(for: commandLine)
 
     return try inputs.reduce(into: [:]) { keys, input in
       keys[input.0] = try cas.computeCacheKey(commandLine: arguments, index: input.1)
@@ -972,8 +984,7 @@ extension Driver {
       return nil
     }
     // Resolve command-line first.
-    let resolver = try ArgsResolver(fileSystem: fileSystem)
-    let arguments: [String] = try resolver.resolveArgumentList(for: commandLine)
+    let arguments: [String] = try executor.resolver.resolveArgumentList(for: commandLine)
     return try cas.computeCacheKey(commandLine: arguments, index: index)
   }
 }

Sources/SwiftDriver/Jobs/VerifyModuleInterfaceJob.swift

@@ -35,7 +35,7 @@ extension Driver {
     var inputs: [TypedVirtualPath] = [interfaceInput]
     commandLine.appendFlags("-frontend", "-typecheck-module-from-interface")
     try addPathArgument(interfaceInput.file, to: &commandLine)
-    try addCommonFrontendOptions(commandLine: &commandLine, inputs: &inputs, kind: .verifyModuleInterface)
+    try addCommonFrontendOptions(commandLine: &commandLine, inputs: &inputs, kind: .verifyModuleInterface, bridgingHeaderHandling: .ignored)
     // FIXME: MSVC runtime flags
 
     // Output serialized diagnostics for this job, if specifically requested

Sources/SwiftDriver/SwiftScan/DependencyGraphBuilder.swift

@@ -184,6 +184,10 @@ private extension SwiftScan {
     let isFramework = api.swiftscan_swift_textual_detail_get_is_framework(moduleDetailsRef)
     let moduleCacheKey = supportsCaching ?  try getOptionalStringDetail(from: moduleDetailsRef,
                                                      using: api.swiftscan_swift_textual_detail_get_module_cache_key) : nil
+    let chainedBridgingHeaderPath = supportsChainedBridgingHeader ?
+      try getOptionalStringDetail(from: moduleDetailsRef, using: api.swiftscan_swift_textual_detail_get_chained_bridging_header_path) : nil
+    let chainedBridgingHeaderContent = supportsChainedBridgingHeader ?
+      try getOptionalStringDetail(from: moduleDetailsRef, using: api.swiftscan_swift_textual_detail_get_chained_bridging_header_content) : nil
 
     // Decode all dependencies of this module
     let swiftOverlayDependencies: [ModuleDependencyId]?
@@ -204,7 +208,9 @@ private extension SwiftScan {
                               contextHash: contextHash,
                               isFramework: isFramework,
                               swiftOverlayDependencies: swiftOverlayDependencies,
-                              moduleCacheKey: moduleCacheKey)
+                              moduleCacheKey: moduleCacheKey,
+                              chainedBridgingHeaderPath: chainedBridgingHeaderPath,
+                              chainedBridgingHeaderContent: chainedBridgingHeaderContent)
   }
 
   /// Construct a `SwiftPrebuiltExternalModuleDetails` from a `swiftscan_module_details_t` reference