Add SDK and platform paths to plugin executables

Author: DougGregor

Sources/SwiftDriver/Jobs/FrontendJobHelpers.swift

@@ -27,6 +27,26 @@ fileprivate func shouldColorDiagnostics() -> Bool {
   return TerminalController.isTTY(stderrStream)
 }
 
+extension VirtualPath {
+  // Given a virtual path pointing into a toolchain/SDK/platform, produce the
+  // path to `swift-plugin-server`.
+  fileprivate var pluginServerPath: VirtualPath {
+    self.appending(components: "usr", "swift-plugin-server")
+  }
+
+  // Given a virtual path pointing into a toolchain/SDK/platform, produce the
+  // path to the plugins.
+  fileprivate var pluginPath: VirtualPath {
+    self.appending(components: "lib", "swift", "host", "plugins")
+  }
+
+  // Given a virtual path pointing into a toolchain/SDK/platform, produce the
+  // path to the plugins.
+  fileprivate var localPluginPath: VirtualPath {
+    self.appending(component: "local").pluginPath
+  }
+}
+
 extension Driver {
   /// How the bridging header should be handled.
   enum BridgingHeaderHandling {
@@ -261,18 +281,46 @@ extension Driver {
       try commandLine.appendLast(.emitMacroExpansionFiles, from: &parsedOptions)
     }
 
-    if isFrontendArgSupported(.pluginPath) {
+    // Emit user-provided plugin paths, in order.
+    if isFrontendArgSupported(.externalPluginPath) {
+      try commandLine.appendAll(.pluginPath, .externalPluginPath, from: &parsedOptions)
+    } else if isFrontendArgSupported(.pluginPath) {
       try commandLine.appendAll(.pluginPath, from: &parsedOptions)
+    }
+
+    if isFrontendArgSupported(.externalPluginPath), let sdkPath = frontendTargetInfo.sdkPath?.path {
+      // Default paths for compiler plugins found within an SDK (accessed via
+      // that SDK's plugin server).
+      let sdkPathRoot = VirtualPath.lookup(sdkPath).appending(components: "usr")
+      commandLine.appendFlag(.externalPluginPath)
+      commandLine.appendFlag("\(sdkPathRoot.pluginServerPath.name.spm_shellEscaped())#\(sdkPathRoot.pluginPath.name)")
+
+      commandLine.appendFlag(.externalPluginPath)
+      commandLine.appendFlag("\(sdkPathRoot.pluginServerPath.name.spm_shellEscaped())#\(sdkPathRoot.localPluginPath.name)")
 
-      let defaultPluginPath = try toolchain.executableDir.parentDirectory
-        .appending(components: "lib", "swift", "host", "plugins")
+      // Default paths for compiler plugins within the platform (accessed via that
+      // platform's plugin server).
+      let platformPathRoot = VirtualPath.lookup(sdkPath)
+        .parentDirectory
+        .parentDirectory
+        .parentDirectory
+        .appending(components: "Developer", "usr")
+      commandLine.appendFlag(.externalPluginPath)
+      commandLine.appendFlag("\(platformPathRoot.pluginServerPath.name.spm_shellEscaped())#\(platformPathRoot.pluginPath.name)")
+
+      commandLine.appendFlag(.externalPluginPath)
+      commandLine.appendFlag("\(platformPathRoot.pluginServerPath.name.spm_shellEscaped())#\(platformPathRoot.localPluginPath.name)")
+    }
+
+    if isFrontendArgSupported(.pluginPath) {
+      // Default paths for compiler plugins found within the toolchain
+      // (loaded as shared libraries).
+      let pluginPathRoot = VirtualPath.absolute(try toolchain.executableDir.parentDirectory)
       commandLine.appendFlag(.pluginPath)
-      commandLine.appendPath(defaultPluginPath)
+      commandLine.appendPath(pluginPathRoot.pluginPath)
 
-      let localPluginPath = try toolchain.executableDir.parentDirectory
-        .appending(components: "local", "lib", "swift", "host", "plugins")
       commandLine.appendFlag(.pluginPath)
-      commandLine.appendPath(localPluginPath)
+      commandLine.appendPath(pluginPathRoot.localPluginPath)
     }
 
     if isFrontendArgSupported(.externalPluginPath) {

Tests/SwiftDriverTests/SwiftDriverTests.swift

@@ -6798,14 +6798,16 @@ final class SwiftDriverTests: XCTestCase {
   }
 
   func testPluginPaths() throws {
-    var driver = try Driver(args: ["swiftc", "-typecheck", "foo.swift"])
-    guard driver.isFrontendArgSupported(.pluginPath) else {
+    let sdkRoot = testInputsPath.appending(component: "SDKChecks").appending(component: "iPhoneOS.sdk")
+    var driver = try Driver(args: ["swiftc", "-typecheck", "foo.swift", "-sdk", VirtualPath.absolute(sdkRoot).name])
+    guard driver.isFrontendArgSupported(.pluginPath) && driver.isFrontendArgSupported(.externalPluginPath) else {
       return
     }
 
     let jobs = try driver.planBuild().removingAutolinkExtractJobs()
     XCTAssertEqual(jobs.count, 1)
     let job = jobs.first!
+    XCTAssertTrue(job.commandLine.contains(.flag("-external-plugin-path")))
     XCTAssertTrue(job.commandLine.contains(.flag("-plugin-path")))
     XCTAssertTrue(job.commandLine.contains(.path(.absolute(try driver.toolchain.executableDir.parentDirectory.appending(components: "lib", "swift", "host", "plugins")))))
     XCTAssertTrue(job.commandLine.contains(.path(.absolute(try driver.toolchain.executableDir.parentDirectory.appending(components: "local", "lib", "swift", "host", "plugins")))))