swiftlang · cachemeifyoucan · Apr 11, 2025 · Apr 2, 2025
diff --git a/Sources/SwiftDriver/ExplicitModuleBuilds/ExplicitDependencyBuildPlanner.swift b/Sources/SwiftDriver/ExplicitModuleBuilds/ExplicitDependencyBuildPlanner.swift
@@ -53,6 +53,7 @@ public typealias ExternalTargetModuleDetailsMap = [ModuleDependencyId: ExternalT
   private let mainModuleName: String?
   private let cas: SwiftScanCAS?
   private let swiftScanOracle: InterModuleDependencyOracle
+  private let prefixMap: [(AbsolutePath, AbsolutePath)]
 
   /// Clang PCM names contain a hash of the command-line arguments that were used to build them.
   /// We avoid re-running the hash computation with the use of this cache
@@ -73,7 +74,8 @@ public typealias ExternalTargetModuleDetailsMap = [ModuleDependencyId: ExternalT
               dependencyOracle: InterModuleDependencyOracle,
               integratedDriver: Bool = true,
               supportsExplicitInterfaceBuild: Bool = false,
-              cas: SwiftScanCAS? = nil) throws {
+              cas: SwiftScanCAS? = nil,
+              prefixMap:  [(AbsolutePath, AbsolutePath)] = []) throws {
     self.dependencyGraph = dependencyGraph
     self.toolchain = toolchain
     self.swiftScanOracle = dependencyOracle
@@ -82,6 +84,7 @@ public typealias ExternalTargetModuleDetailsMap = [ModuleDependencyId: ExternalT
     self.reachabilityMap = try dependencyGraph.computeTransitiveClosure()
     self.supportsExplicitInterfaceBuild = supportsExplicitInterfaceBuild
     self.cas = cas
+    self.prefixMap = prefixMap
   }
 
   /// Supports resolving bridging header pch command from swiftScan.
@@ -185,6 +188,12 @@ public typealias ExternalTargetModuleDetailsMap = [ModuleDependencyId: ExternalT
         }
       }
 
+      // Add prefix mapping. The option is cache invariant so it can be added without affecting cache key.
+      for (key, value) in prefixMap {
+        commandLine.appendFlag("-cache-replay-prefix-map")
+        commandLine.appendFlag(value.pathString + "=" + key.pathString)
+      }
+
       jobs.append(Job(
         moduleName: moduleId.moduleName,
         kind: .compileModuleFromInterface,
@@ -238,6 +247,12 @@ public typealias ExternalTargetModuleDetailsMap = [ModuleDependencyId: ExternalT
         cacheKeys = [:]
       }
 
+      // Add prefix mapping. The option is cache invariant so it can be added without affecting cache key.
+      for (key, value) in prefixMap {
+        commandLine.appendFlag("-cache-replay-prefix-map")
+        commandLine.appendFlag(value.pathString + "=" + key.pathString)
+      }
+
       jobs.append(Job(
         moduleName: moduleId.moduleName,
         kind: .generatePCM,

diff --git a/Sources/SwiftDriver/ExplicitModuleBuilds/ModuleDependencyScanning.swift b/Sources/SwiftDriver/ExplicitModuleBuilds/ModuleDependencyScanning.swift
@@ -195,6 +195,10 @@ public extension Driver {
       }
     }
 
+    if isFrontendArgSupported(.resolvedPluginVerification) {
+      commandLine.appendFlag(.resolvedPluginVerification)
+    }
+
     // Pass on the input files
     commandLine.append(contentsOf: inputFiles.filter { $0.type == .swift }.map { .path($0.file) })
     return (inputs, commandLine)

diff --git a/Sources/SwiftDriver/Jobs/FrontendJobHelpers.swift b/Sources/SwiftDriver/Jobs/FrontendJobHelpers.swift
@@ -84,12 +84,13 @@ extension Driver {
       break
     }
 
+    let isPlanJobForExplicitModule = parsedOptions.contains(.driverExplicitModuleBuild) &&
+                                     moduleDependencyGraphUse == .computed
     let jobNeedPathRemap: Bool
     // If in ExplicitModuleBuild mode and the dependency graph has been computed, add module
     // dependencies.
     // May also be used for generation of the dependency graph itself in ExplicitModuleBuild mode.
-    if (parsedOptions.contains(.driverExplicitModuleBuild) &&
-          moduleDependencyGraphUse == .computed) {
+    if isPlanJobForExplicitModule {
       switch kind {
       case .generatePCH:
         try addExplicitPCHBuildArguments(inputs: &inputs, commandLine: &commandLine)
@@ -344,10 +345,12 @@ extension Driver {
     }
 
     // Emit user-provided plugin paths, in order.
-    if isFrontendArgSupported(.externalPluginPath) {
-      try commandLine.appendAll(.pluginPath, .externalPluginPath, .loadPluginLibrary, .loadPluginExecutable, from: &parsedOptions)
-    } else if isFrontendArgSupported(.pluginPath) {
-      try commandLine.appendAll(.pluginPath, .loadPluginLibrary, from: &parsedOptions)
+    if !isPlanJobForExplicitModule {
+      if isFrontendArgSupported(.externalPluginPath) {
+        try commandLine.appendAll(.pluginPath, .externalPluginPath, .loadPluginLibrary, .loadPluginExecutable, from: &parsedOptions)
+      } else if isFrontendArgSupported(.pluginPath) {
+        try commandLine.appendAll(.pluginPath, .loadPluginLibrary, from: &parsedOptions)
+      }
     }
 
     if isFrontendArgSupported(.blockListFile) {
@@ -563,19 +566,22 @@ extension Driver {
       .appending(components: frontendTargetInfo.target.triple.platformName() ?? "", "Swift.swiftmodule")
     let hasToolchainStdlib = try fileSystem.exists(toolchainStdlibPath)
 
+    let skipMacroOptions = isPlanJobForExplicitModule && isFrontendArgSupported(.loadResolvedPlugin)
     // If the resource directory has the standard library, prefer the toolchain's plugins
     // to the platform SDK plugins.
-    if hasToolchainStdlib {
+    // For explicit module build, the resolved plugins are provided by scanner.
+    if hasToolchainStdlib, !skipMacroOptions {
       try addPluginPathArguments(commandLine: &commandLine)
     }
 
     try toolchain.addPlatformSpecificCommonFrontendOptions(commandLine: &commandLine,
                                                            inputs: &inputs,
                                                            frontendTargetInfo: frontendTargetInfo,
-                                                           driver: &self)
+                                                           driver: &self,
+                                                           skipMacroOptions: skipMacroOptions)
 
     // Otherwise, prefer the platform's plugins.
-    if !hasToolchainStdlib {
+    if !hasToolchainStdlib, !skipMacroOptions {
       try addPluginPathArguments(commandLine: &commandLine)
     }
 

diff --git a/Sources/SwiftDriver/Jobs/Planning.swift b/Sources/SwiftDriver/Jobs/Planning.swift
@@ -688,7 +688,8 @@ extension Driver {
                                          integratedDriver: integratedDriver,
                                          supportsExplicitInterfaceBuild:
                                          isFrontendArgSupported(.explicitInterfaceModuleBuild),
-                                         cas: cas)
+                                         cas: cas,
+                                         prefixMap: prefixMapping)
 
     return try explicitDependencyBuildPlanner!.generateExplicitModuleDependenciesBuildJobs()
   }

diff --git a/Sources/SwiftDriver/Toolchains/DarwinToolchain.swift b/Sources/SwiftDriver/Toolchains/DarwinToolchain.swift
@@ -392,7 +392,8 @@ public final class DarwinToolchain: Toolchain {
     commandLine: inout [Job.ArgTemplate],
     inputs: inout [TypedVirtualPath],
     frontendTargetInfo: FrontendTargetInfo,
-    driver: inout Driver
+    driver: inout Driver,
+    skipMacroOptions: Bool
   ) throws {
     guard let sdkPath = frontendTargetInfo.sdkPath?.path,
           let sdkInfo = getTargetSDKInfo(sdkPath: sdkPath) else { return }
@@ -477,7 +478,7 @@ public final class DarwinToolchain: Toolchain {
       }
     }
 
-    if driver.isFrontendArgSupported(.externalPluginPath) {
+    if driver.isFrontendArgSupported(.externalPluginPath) && !skipMacroOptions {
       // If the PLATFORM_DIR environment variable is set, also add plugin
       // paths into it. Since this is a user override, it comes beore the
       // default platform path that's based on the SDK.

diff --git a/Sources/SwiftDriver/Toolchains/GenericUnixToolchain.swift b/Sources/SwiftDriver/Toolchains/GenericUnixToolchain.swift
@@ -150,7 +150,8 @@ public final class GenericUnixToolchain: Toolchain {
     commandLine: inout [Job.ArgTemplate],
     inputs: inout [TypedVirtualPath],
     frontendTargetInfo: FrontendTargetInfo,
-    driver: inout Driver
+    driver: inout Driver,
+    skipMacroOptions: Bool
   ) throws {
     if let sysroot = driver.parsedOptions.getLastArgument(.sysroot)?.asSingle {
       commandLine.appendFlag("-sysroot")

diff --git a/Sources/SwiftDriver/Toolchains/Toolchain.swift b/Sources/SwiftDriver/Toolchains/Toolchain.swift
@@ -154,7 +154,8 @@ public protocol Toolchain {
     commandLine: inout [Job.ArgTemplate],
     inputs: inout [TypedVirtualPath],
     frontendTargetInfo: FrontendTargetInfo,
-    driver: inout Driver
+    driver: inout Driver,
+    skipMacroOptions: Bool
   ) throws
 
   var dummyForTestingObjectFormat: Triple.ObjectFormat {get}
@@ -326,7 +327,8 @@ extension Toolchain {
     commandLine: inout [Job.ArgTemplate],
     inputs: inout [TypedVirtualPath],
     frontendTargetInfo: FrontendTargetInfo,
-    driver: inout Driver
+    driver: inout Driver,
+    skipMacroOptions: Bool
   ) throws {}
 
   /// Resolves the path to the given tool and whether or not it supports response files so that it

diff --git a/Sources/SwiftOptions/Options.swift b/Sources/SwiftOptions/Options.swift
diff --git a/Tests/SwiftDriverTests/CachingBuildTests.swift b/Tests/SwiftDriverTests/CachingBuildTests.swift
@@ -939,6 +939,10 @@ final class CachingBuildTests: XCTestCase {
         XCTAssertFalse(try command.contains {
           $0.starts(with: try testInputsPath.description)
         })
+        /// command-line that compiles swift should contains -cache-replay-prefix-map
+        XCTAssertTrue(command.contains { $0 == "-cache-replay-prefix-map" })
+        XCTAssertFalse(command.contains { $0 == "-plugin-path" || $0 == "-external-plugin-path" ||
+                                          $0 == "-load-plugin-library" || $0 == "-load-plugin-executable" })
       }
     }
   }