Fixup linker input handling and use -add_ast_path when needed

Author: owenv

Sources/SwiftDriver/Jobs/DarwinToolchain+LinkerSupport.swift

@@ -303,7 +303,16 @@ extension DarwinToolchain {
     }
 
     // Add inputs.
-    commandLine.append(contentsOf: inputs.map { .path($0.file) })
+    commandLine.append(contentsOf: inputs.flatMap {
+      (path: TypedVirtualPath) -> [Job.ArgTemplate] in
+      if path.type == .swiftModule {
+        return [.flag("-add_ast_path"), .path(path.file)]
+      } else if path.type == .object {
+        return [.path(path.file)]
+      } else {
+        return []
+      }
+    })
 
     // Add the output
     commandLine.appendFlag("-o")

Sources/SwiftDriver/Jobs/GenericUnixToolchain+LinkerSupport.swift

@@ -158,12 +158,15 @@ extension GenericUnixToolchain {
         )
       commandLine.appendPath(swiftrtPath)
 
-      let inputFiles: [Job.ArgTemplate] = inputs.map { input in
+      let inputFiles: [Job.ArgTemplate] = inputs.compactMap { input in
         // Autolink inputs are handled specially
         if input.type == .autolink {
           return .responseFilePath(input.file)
+        } else if input.type == .object {
+          return .path(input.file)
+        } else {
+          return nil
         }
-        return .path(input.file)
       }
       commandLine.append(contentsOf: inputFiles)
 

Tests/SwiftDriverTests/SwiftDriverTests.swift

@@ -832,6 +832,30 @@ final class SwiftDriverTests: XCTestCase {
       XCTAssertFalse(cmd.contains(.flag("-shared")))
     }
 
+    #if os(macOS)
+    // dsymutil won't be found on Linux.
+    do {
+      var driver = try Driver(args: commonArgs + ["-emit-executable", "-emit-module", "-g", "-target", "x86_64-apple-macosx10.15"], env: env)
+      let plannedJobs = try driver.planBuild()
+      XCTAssertEqual(5, plannedJobs.count)
+      XCTAssertEqual(plannedJobs.map(\.kind), [.compile, .compile, .mergeModule, .link, .generateDSYM])
+
+      let linkJob = plannedJobs[3]
+      XCTAssertEqual(linkJob.kind, .link)
+
+      let cmd = linkJob.commandLine
+      XCTAssertTrue(cmd.contains(.flag("-o")))
+      XCTAssertTrue(cmd.contains(.path(.temporary(RelativePath("foo.o")))))
+      XCTAssertTrue(cmd.contains(.path(.temporary(RelativePath("bar.o")))))
+      XCTAssertTrue(cmd.contains(subsequence: [.flag("-add_ast_path"), .path(.relative(.init("Test.swiftmodule")))]))
+      XCTAssertEqual(linkJob.outputs[0].file, try VirtualPath(path: "Test"))
+
+      XCTAssertFalse(cmd.contains(.flag("-static")))
+      XCTAssertFalse(cmd.contains(.flag("-dylib")))
+      XCTAssertFalse(cmd.contains(.flag("-shared")))
+    }
+    #endif
+
     // FIXME: This test will fail when run on macOS, because
     // swift-autolink-extract is not present
     #if os(Linux)