Add clang-tidy-fix target

Add the `clang-tidy-fix` target to apply clang-tidy fixes to the source
code.
This is done by calling `run-clang-tidy` with `-fix` argument.

Add a test case to run `clang-tidy-fix` and verify the file is changed.

Signed-off-by: Lei YU <yulei.sh@bytedance.com>

5 files changed, 41 insertions, 3 deletions

diff --git a/docs/markdown/snippets/meson_clang_tidy_fix.md b/docs/markdown/snippets/meson_clang_tidy_fix.md
new file mode 100644
index 0000000..3a8c772
--- /dev/null
+++ b/docs/markdown/snippets/meson_clang_tidy_fix.md
@@ -0,0 +1,9 @@
+## clang-tidy-fix target
+
+If `clang-tidy` is installed and the project's source root contains a
+`.clang-tidy` (or `_clang-tidy`) file, Meson will automatically define
+a `clang-tidy-fix` target that runs `run-clang-tidy` tool with `-fix`
+option to apply the changes found by clang-tidy to the source code.
+
+If you have defined your own `clang-tidy-fix` target, Meson will not
+generate its own target.
diff --git a/mesonbuild/backend/ninjabackend.py b/mesonbuild/backend/ninjabackend.py
index a57b249..925941a 100644
--- a/mesonbuild/backend/ninjabackend.py
+++ b/mesonbuild/backend/ninjabackend.py
@@ -3659,6 +3659,7 @@ https://gcc.gnu.org/bugzilla/show_bug.cgi?id=47485'''))
         if not shutil.which('clang-tidy'):
             return
         self.generate_clangtool('tidy')
+        self.generate_clangtool('tidy', 'fix')
 
     def generate_tags(self, tool: str, target_name: str) -> None:
         import shutil
diff --git a/mesonbuild/scripts/clangtidy.py b/mesonbuild/scripts/clangtidy.py
index 324a26e..943bde5 100644
--- a/mesonbuild/scripts/clangtidy.py
+++ b/mesonbuild/scripts/clangtidy.py
@@ -23,8 +23,12 @@ import typing as T
 def run_clang_tidy(fname: Path, builddir: Path) -> subprocess.CompletedProcess:
     return subprocess.run(['clang-tidy', '-p', str(builddir), str(fname)])
 
+def run_clang_tidy_fix(fname: Path, builddir: Path) -> subprocess.CompletedProcess:
+    return subprocess.run(['run-clang-tidy', '-fix', '-format', '-quiet', '-p', str(builddir), str(fname)])
+
 def run(args: T.List[str]) -> int:
     parser = argparse.ArgumentParser()
+    parser.add_argument('--fix', action='store_true')
     parser.add_argument('sourcedir')
     parser.add_argument('builddir')
     options = parser.parse_args(args)
@@ -32,4 +36,5 @@ def run(args: T.List[str]) -> int:
     srcdir = Path(options.sourcedir)
     builddir = Path(options.builddir)
 
-    return run_tool('clang-tidy', srcdir, builddir, run_clang_tidy, builddir)
+    run_func = run_clang_tidy_fix if options.fix else run_clang_tidy
+    return run_tool('clang-tidy', srcdir, builddir, run_func, builddir)
diff --git a/unittests/allplatformstests.py b/unittests/allplatformstests.py
index acab026..f06279a 100644
--- a/unittests/allplatformstests.py
+++ b/unittests/allplatformstests.py
@@ -42,7 +42,7 @@ from mesonbuild.mesonlib import (
     is_sunos, windows_proof_rmtree, python_command, version_compare, split_args, quote_arg,
     relpath, is_linux, git, search_version, do_conf_file, do_conf_str, default_prefix,
     MesonException, EnvironmentException, OptionKey,
-    windows_proof_rm
+    windows_proof_rm, quiet_git
 )
 from mesonbuild.programs import ExternalProgram
 
@@ -3029,6 +3029,26 @@ class AllPlatformTests(BasePlatformTests):
         self.assertIn('cttest.cpp:4:20', out)
         self.assertNotIn(dummydir, out)
 
+    @skipIfNoExecutable('clang-tidy')
+    @unittest.skipIf(not is_git_repo(), 'Skipping because this is not in git repo')
+    def test_clang_tidy_fix(self):
+        if self.backend is not Backend.ninja:
+            raise SkipTest(f'Clang-tidy is for now only supported on Ninja, not {self.backend.name}')
+        if shutil.which('c++') is None:
+            raise SkipTest('Clang-tidy breaks when ccache is used and "c++" not in path.')
+        if is_osx():
+            raise SkipTest('Apple ships a broken clang-tidy that chokes on -pipe.')
+        testdir = os.path.join(self.unit_test_dir, '68 clang-tidy')
+        dummydir = os.path.join(testdir, 'dummydir.h')
+        self.init(testdir, override_envvars={'CXX': 'c++'})
+        out = self.run_target('clang-tidy-fix')
+        self.assertIn('cttest.cpp:4:20', out)
+        self.assertNotIn(dummydir, out)
+        ret = quiet_git(['diff', '--exit-code', 'test cases/unit/68 clang-tidy/cttest.cpp'], '.')
+        self.assertFalse(ret[0])
+        # Restore the file
+        quiet_git(['checkout', '--', 'test cases/unit/68 clang-tidy/cttest.cpp'], '.')
+
     def test_identity_cross(self):
         testdir = os.path.join(self.unit_test_dir, '69 cross')
         # Do a build to generate a cross file where the host is this target
diff --git a/unittests/helpers.py b/unittests/helpers.py
index 7483f51..83327cb 100644
--- a/unittests/helpers.py
+++ b/unittests/helpers.py
@@ -12,7 +12,7 @@ from contextlib import contextmanager
 from mesonbuild.compilers import detect_c_compiler, compiler_from_language
 from mesonbuild.mesonlib import (
     MachineChoice, is_osx, is_cygwin, EnvironmentException, OptionKey, MachineChoice,
-    OrderedSet
+    OrderedSet, quiet_git
 )
 from run_tests import get_fake_env
 
@@ -135,6 +135,9 @@ def is_tarball():
         return True
     return False
 
+def is_git_repo():
+    return quiet_git(['branch'], '.')[0]
+
 @contextmanager
 def chdir(path: str):
     curdir = os.getcwd()