[test/ffi] Make the test generator async

The `dart format` step takes 8 seconds currently on the large files.
This cuts down the total time from 21 seconds to 9 on my machine.

TEST=This only changes the test generator, nothing should change.

Bug: https://github.com/dart-lang/sdk/issues/45007

Change-Id: Ie4940fdd3a43a923ca28cb39b0673cc19f81a10a
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/216664
Auto-Submit: Daco Harkes <dacoharkes@google.com>
Reviewed-by: Clement Skau <cskau@google.com>

runtime/bin/ffi_test/ffi_test_functions_generated.cc

@@ -3,6 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 //
 // This file has been automatically generated. Please do not edit it manually.
+// Generated by tests/ffi/generator/structs_by_value_tests_generator.dart.
 
 #include <stddef.h>
 #include <stdlib.h>

tests/ffi/function_callbacks_structs_by_value_generated_test.dart

@@ -3,6 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 //
 // This file has been automatically generated. Please do not edit it manually.
+// Generated by tests/ffi/generator/structs_by_value_tests_generator.dart.
 //
 // SharedObjects=ffi_test_functions
 // VMOptions=

tests/ffi/function_structs_by_value_generated_test.dart

@@ -3,6 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 //
 // This file has been automatically generated. Please do not edit it manually.
+// Generated by tests/ffi/generator/structs_by_value_tests_generator.dart.
 //
 // SharedObjects=ffi_test_functions
 // VMOptions=

tests/ffi/generator/structs_by_value_tests_generator.dart

@@ -870,6 +870,7 @@ headerDartCallTest(bool nnbd) {
 // BSD-style license that can be found in the LICENSE file.
 //
 // This file has been automatically generated. Please do not edit it manually.
+// Generated by tests/ffi/generator/structs_by_value_tests_generator.dart.
 //
 // SharedObjects=ffi_test_functions
 // VMOptions=
@@ -890,8 +891,8 @@ final ffiTestFunctions = dlopenPlatformSpecific("ffi_test_functions");
 """;
 }
 
-void writeDartCallTest() {
-  for (bool nnbd in [true, false]) {
+Future<void> writeDartCallTest() async {
+  await Future.wait([true, false].map((nnbd) async {
     final StringBuffer buffer = StringBuffer();
     buffer.write(headerDartCallTest(nnbd));
 
@@ -908,9 +909,9 @@ void writeDartCallTest() {
     buffer.writeAll(functions.map((e) => e.dartCallCode(isLeaf: true)));
 
     final path = callTestPath(nnbd);
-    File(path).writeAsStringSync(buffer.toString());
-    Process.runSync("dart", ["format", path]);
-  }
+    await File(path).writeAsString(buffer.toString());
+    await runProcess("dart", ["format", path]);
+  }));
 }
 
 String callTestPath(bool nnbd) {
@@ -929,6 +930,7 @@ headerDartCallbackTest(bool nnbd) {
 // BSD-style license that can be found in the LICENSE file.
 //
 // This file has been automatically generated. Please do not edit it manually.
+// Generated by tests/ffi/generator/structs_by_value_tests_generator.dart.
 //
 // SharedObjects=ffi_test_functions
 // VMOptions=
@@ -960,8 +962,8 @@ void main() {
 """;
 }
 
-void writeDartCallbackTest() {
-  for (bool nnbd in [true, false]) {
+Future<void> writeDartCallbackTest() async {
+  await Future.wait([true, false].map((nnbd) async {
     final StringBuffer buffer = StringBuffer();
     buffer.write(headerDartCallbackTest(nnbd));
 
@@ -974,9 +976,9 @@ void writeDartCallbackTest() {
     buffer.writeAll(functions.map((e) => e.dartCallbackCode(nnbd)));
 
     final path = callbackTestPath(nnbd);
-    File(path).writeAsStringSync(buffer.toString());
-    Process.runSync("dart", ["format", path]);
-  }
+    await File(path).writeAsString(buffer.toString());
+    await runProcess("dart", ["format", path]);
+  }));
 }
 
 String callbackTestPath(bool nnbd) {
@@ -993,6 +995,7 @@ const headerC = """
 // BSD-style license that can be found in the LICENSE file.
 //
 // This file has been automatically generated. Please do not edit it manually.
+// Generated by tests/ffi/generator/structs_by_value_tests_generator.dart.
 
 #include <stddef.h>
 #include <stdlib.h>
@@ -1031,7 +1034,7 @@ const footerC = """
 }  // namespace dart
 """;
 
-void writeC() {
+Future<void> writeC() async {
   final StringBuffer buffer = StringBuffer();
   buffer.write(headerC);
 
@@ -1041,8 +1044,8 @@ void writeC() {
 
   buffer.write(footerC);
 
-  File(ccPath).writeAsStringSync(buffer.toString());
-  Process.runSync("clang-format", ["-i", ccPath]);
+  await File(ccPath).writeAsString(buffer.toString());
+  await runProcess("clang-format", ["-i", ccPath]);
 }
 
 final ccPath = Platform.script
@@ -1062,13 +1065,37 @@ Generates:
 """);
 }
 
-void main(List<String> arguments) {
+void main(List<String> arguments) async {
   if (arguments.length != 0) {
     printUsage();
     return;
   }
 
-  writeDartCallTest();
-  writeDartCallbackTest();
-  writeC();
+  await Future.wait([
+    writeDartCallTest(),
+    writeDartCallbackTest(),
+    writeC(),
+  ]);
+}
+
+Future<void> runProcess(String executable, List<String> arguments) async {
+  final commandString = [executable, ...arguments].join(' ');
+  stdout.writeln('Running `$commandString`.');
+  final process = await Process.start(
+    executable,
+    arguments,
+    runInShell: true,
+    includeParentEnvironment: true,
+  ).then((process) {
+    process.stdout.forEach((data) => stdout.add(data));
+    process.stderr.forEach((data) => stderr.add(data));
+    return process;
+  });
+  final exitCode = await process.exitCode;
+  if (exitCode != 0) {
+    final message = 'Command `$commandString` failed with exit code $exitCode.';
+    stderr.writeln(message);
+    throw Exception(message);
+  }
+  stdout.writeln('Command `$commandString` done.');
 }

tests/ffi_2/function_callbacks_structs_by_value_generated_test.dart

@@ -3,6 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 //
 // This file has been automatically generated. Please do not edit it manually.
+// Generated by tests/ffi/generator/structs_by_value_tests_generator.dart.
 //
 // SharedObjects=ffi_test_functions
 // VMOptions=

tests/ffi_2/function_structs_by_value_generated_test.dart

@@ -3,6 +3,7 @@
 // BSD-style license that can be found in the LICENSE file.
 //
 // This file has been automatically generated. Please do not edit it manually.
+// Generated by tests/ffi/generator/structs_by_value_tests_generator.dart.
 //
 // SharedObjects=ffi_test_functions
 // VMOptions=