Multithreading tests and diagnostics

Sources/SwiftDriver/Driver/Driver.swift

@@ -707,7 +707,7 @@ extension Driver {
 }
 
 extension Diagnostic.Message {
-  public static func error_i_mode(_ driverKind: DriverKind) -> Diagnostic.Message {
+  static func error_i_mode(_ driverKind: DriverKind) -> Diagnostic.Message {
     .error(
       """
       the flag '-i' is no longer required and has been removed; \
@@ -731,17 +731,14 @@ extension Driver {
 
     // Make sure we have a non-negative integer value.
     guard let numThreads = Int(numThreadsArg.asSingle), numThreads >= 0 else {
-      diagnosticsEngine.emit(Diagnostic.Message.error_invalid_arg_value(arg: .numThreads, value: numThreadsArg.asSingle))
+      diagnosticsEngine.emit(.error_invalid_arg_value(arg: .numThreads, value: numThreadsArg.asSingle))
       return 0
     }
 
-    #if false
-    // FIXME: Check for batch mode.
-    if false {
+    if case .batchCompile = compilerMode {
       diagnosticsEngine.emit(.warning_cannot_multithread_batch_mode)
       return 0
     }
-    #endif
 
     return numThreads
   }

Tests/SwiftDriverTests/SwiftDriverTests.swift

@@ -144,10 +144,59 @@ final class SwiftDriverTests: XCTestCase {
 
   func testPrimaryOutputKindsDiagnostics() throws {
       try assertDriverDiagnostics(args: "swift", "-i") {
-          $1.expect(.error_i_mode(.interactive))
+        $1.expect(.error("the flag '-i' is no longer required and has been removed; use 'swift input-filename'"))
       }
   }
 
+    func testMultithreading() throws {
+
+      XCTAssertEqual(try Driver(args: ["swiftc"]).numThreads, 0)
+
+      XCTAssertEqual(try Driver(args: ["swiftc", "-num-threads", "4"]).numThreads, 4)
+
+      XCTAssertEqual(try Driver(args: ["swiftc", "-num-threads", "0"]).numThreads, 0)
+
+      XCTAssertEqual(try Driver(args: ["swiftc", "-num-threads", "-1"]).numThreads, 0)
+
+      XCTAssertEqual(try Driver(args: ["swiftc", "-enable-batch-mode", "-num-threads", "4"]).numThreads, 0)
+
+      XCTAssertNil(try Driver(args: ["swiftc"]).numParallelJobs)
+
+      XCTAssertEqual(try Driver(args: ["swiftc", "-j", "4"]).numParallelJobs, 4)
+
+      XCTAssertNil(try Driver(args: ["swiftc", "-j", "0"]).numParallelJobs)
+
+      XCTAssertEqual(
+        try Driver(
+          args: ["swiftc", "-j", "4", "-target", "x86_64-apple-macosx10.15"],
+          env: ["SWIFTC_MAXIMUM_DETERMINISM": "1"]
+        ).numParallelJobs,
+        1
+      )
+    }
+
+    func testMultithreadingDiagnostics() throws {
+
+      try assertDriverDiagnostics(args: "swift", "-num-threads", "-1") {
+        $1.expect(.error_invalid_arg_value(arg: .numThreads, value: "-1"))
+      }
+
+      try assertDriverDiagnostics(args: "swiftc", "-enable-batch-mode", "-num-threads", "4") {
+        $1.expect(.warning("ignoring -num-threads argument; cannot multithread batch mode"))
+      }
+
+      try assertDriverDiagnostics(args: "swiftc", "-j", "0") {
+        $1.expect(.error_invalid_arg_value(arg: .j, value: "0"))
+      }
+
+      try assertDriverDiagnostics(
+        args: "swiftc", "-j", "8", "-target", "x86_64-apple-macosx10.15",
+        env: ["SWIFTC_MAXIMUM_DETERMINISM": "1"]
+      ) {
+        $1.expect(.remark("SWIFTC_MAXIMUM_DETERMINISM overriding -j"))
+      }
+    }
+
   func testDebugSettings() throws {
     try assertNoDriverDiagnostics(args: "swiftc", "foo.swift", "-emit-module") { driver in
       XCTAssertNil(driver.debugInfoLevel)