Enable colors in FileCheck and Swift tests

If we're attached to a tty, pass `--color` to
FileCheck and `--color-diagnostics` to Swift
invocations in tests.

test/lit.cfg

@@ -365,6 +365,8 @@ config.abi_symbol_checker = make_path(config.swift_utils, 'swift-abi-symbol-chec
 config.link = lit.util.which('link', config.environment.get('PATH', '')) or      \
               lit.util.which('lld-link', config.environment.get('PATH', ''))
 
+config.color_output = lit_config.params.get('color_output', None) is not None
+
 # Find the resource directory.  Assume it's near the swift compiler if not set.
 test_resource_dir = lit_config.params.get('test_resource_dir')
 config.resource_dir_opt = ""
@@ -1953,6 +1955,10 @@ config.substitutions.append(('%cache-tool', config.swift_cache_tool))
 config.target_swift_frontend += " -typo-correction-limit 10 "
 subst_target_swift_frontend_mock_sdk += " -typo-correction-limit 10 "
 
+# Enable colors if we have them.
+if config.color_output:
+    config.target_swift_frontend += " -color-diagnostics"
+
 config.substitutions.append(('%module-target-triple',
                              target_specific_module_triple))
 config.substitutions.append(('%module-target-future', target_future))
@@ -2728,7 +2734,7 @@ if hasattr(config, 'target_link_sdk_future_version'):
     config.substitutions.append(('%target-link-sdk-future-version',
                                  config.target_link_sdk_future_version))
 
-run_filecheck = '%s %s --allow-unused-prefixes --sanitize BUILD_DIR=%s --sanitize SOURCE_DIR=%s --use-filecheck %s %s' % (
+run_filecheck = '%s %s --allow-unused-prefixes --sanitize BUILD_DIR=%s --sanitize SOURCE_DIR=%s --use-filecheck %s %s %s' % (
         shell_quote(sys.executable),
         shell_quote(config.PathSanitizingFileCheck),
         # LLVM Lit performs realpath with the config path, so all paths are relative
@@ -2740,6 +2746,7 @@ run_filecheck = '%s %s --allow-unused-prefixes --sanitize BUILD_DIR=%s --sanitiz
         shell_quote(lit.util.abs_path_preserve_drive(swift_obj_root).replace("\\", "/")),
         shell_quote(lit.util.abs_path_preserve_drive(config.swift_src_root).replace("\\", "/")),
         shell_quote(config.filecheck),
+        '--color' if config.color_output else '',
         '--enable-windows-compatibility' if kIsWindows else '')
 
 config.substitutions.append(('%FileCheck', run_filecheck))

utils/build-script

@@ -313,6 +313,10 @@ def apply_default_arguments(toolchain, args):
     if ninja_required and toolchain.ninja is None:
         args.build_ninja = True
 
+    # Enable test colors if we're on a tty and aren't generating for Xcode.
+    if args.color_in_tests and sys.stdout.isatty() and args.cmake_generator != "Xcode":
+        args.lit_args += " --param color_output"
+
     # Set the default stdlib-deployment-targets, if none were provided.
     if args.stdlib_deployment_targets is None:
         stdlib_targets = default_stdlib_deployment_targets(args)

utils/build_swift/build_swift/driver_arguments.py

@@ -572,6 +572,9 @@ def create_argument_parser():
            metavar='LITARGS',
            help='lit args to use when testing')
 
+    option('--color-in-tests', toggle_true, default=True,
+           help='Enable color output in lit tests')
+
     option('--coverage-db', store_path,
            help='coverage database to use when prioritizing testing')
 

utils/build_swift/tests/expected_options.py

@@ -140,6 +140,7 @@ EXPECTED_DEFAULTS = {
     'cmake_generator': 'Ninja',
     'cmark_assertions': True,
     'cmark_build_variant': 'Debug',
+    'color_in_tests': True,
     'compiler_vendor': defaults.COMPILER_VENDOR,
     'coverage_db': None,
     'cross_compile_append_host_target_to_destdir': True,
@@ -580,6 +581,7 @@ EXPECTED_OPTIONS = [
     EnableOption('--build-swift-remote-mirror'),
     EnableOption('--build-swift-external-generic-metadata-builder'),
     EnableOption('--cross-compile-append-host-target-to-destdir'),
+    EnableOption('--color-in-tests'),
     EnableOption('--distcc'),
     EnableOption('--sccache'),
     EnableOption('--enable-asan'),

utils/run-test

@@ -127,6 +127,8 @@ def main():
     parser.add_argument("--build-jobs",
                         type=int,
                         help="The number of parallel build jobs to use")
+    parser.add_argument("--color", choices=["true", "false"], default="true",
+                        help="Whether to enable color output (default: true)")
     parser.add_argument("--target",
                         type=argparse.types.ShellSplitType(),
                         action=argparse.actions.AppendAction,
@@ -265,6 +267,10 @@ def main():
     for param in args.param:
         test_args += ['--param', param]
 
+    # Enable colors if we're on a tty.
+    if args.color == 'true' and sys.stdout.isatty():
+        test_args += ['--param', 'color_output']
+
     if args.result_dir:
         test_args += ['--param', 'swift_test_results_dir=%s' % args.result_dir,
                       '--xunit-xml-output=%s' % os.path.join(args.result_dir,