Add clang_tidy_tool.py to fetch, build, and invoke clang-tidy

Bug: 936989
Change-Id: I283cbb9f87e912c8094872a70c6abc193659cbe2
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1497198
Reviewed-by: Nico Weber <thakis@chromium.org>
Commit-Queue: Daniel McArdle <dmcardle@chromium.org>
Cr-Commit-Position: refs/heads/master@{#638591}

docs/clang_static_analyzer.md

@@ -29,6 +29,10 @@ You can find the analysis logs in the `compile stdout` step.
 * [Linux buildbot logs](https://ci.chromium.org/p/chromium/builders/luci.chromium.ci/Linux%20Clang%20Analyzer)
 
 ## Enabling static analysis
+
+*Warning:* `use_clang_static_analyzer` is deprecated, but the static analyzer can
+still be invoked with [clang-tidy](clang_tidy.md).
+
 To get static analysis running for your build, add the following flag to your GN
 args.
 

docs/clang_tidy.md

@@ -18,6 +18,14 @@ or bugs that can be deduced via static analysis.
 
 ## Setting Up
 
+### Automatic Setup
+
+The script [clang_tidy_tool.py](../tools/clang/scripts/clang_tidy_tool.py) will
+automatically fetch, build, and invoke `clang-tidy`. To do this manually, follow
+the steps in the next section.
+
+### Manual Setup
+
 In addition to a full Chromium checkout, you need the clang-tidy binary. We
 recommend checking llvm's clang source and building the clang-tidy binary
 directly. Instructions for getting started with clang are available from
@@ -28,7 +36,10 @@ process.
 
 Instead of building with `"Unix Makefiles"`, generate build files for Ninja with
 ```
-cmake -GNinja -DCMAKE_BUILD_TYPE=Release ../llvm
+cmake -GNinja \
+    -DLLVM_ENABLE_PROJECTS=clang;clang-tools-extra \
+    -DCMAKE_BUILD_TYPE=Release \
+    ../llvm
 ```
 
 Then, instead of using `make`, use ninja to build the clang-tidy binary with

tools/clang/scripts/clang_tidy_tool.py

@@ -0,0 +1,186 @@
+#!/usr/bin/env python
+# Copyright 2019 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+r"""Automatically fetch, build, and run clang-tidy from source.
+
+This script seeks to automate the steps detailed in docs/clang_tidy.md.
+
+Example: the following command disables clang-tidy's default checks (-*) and
+enables the clang static analyzer checks.
+
+    tools/clang/scripts/clang_tidy_tool.py \\
+       --checks='-*,clang-analyzer-*,-clang-analyzer-alpha*' \\
+       --header-filter='.*' \\
+       out/Release chrome
+"""
+
+import argparse
+import os
+import subprocess
+import sys
+
+
+def GetCheckoutDir(out_dir):
+  """Returns absolute path to the checked-out llvm repo."""
+  return os.path.join(out_dir, 'tools', 'clang', 'third_party', 'llvm')
+
+
+def GetBuildDir(out_dir):
+  return os.path.join(GetCheckoutDir(out_dir), 'build')
+
+
+def FetchClang(out_dir):
+  """Clone llvm repo into |out_dir| or update if it already exists."""
+  checkout_dir = GetCheckoutDir(out_dir)
+
+  try:
+    # Create parent directories of the checkout directory
+    os.makedirs(os.path.dirname(checkout_dir))
+  except OSError:
+    pass
+
+  try:
+    # First, try to clone the repo.
+    args = [
+        'git',
+        'clone',
+        'https://github.com/llvm/llvm-project.git',
+        checkout_dir,
+    ]
+    subprocess.check_call(args, shell=sys.platform == 'win32')
+  except subprocess.CalledProcessError:
+    # Otherwise, try to update it.
+    print('-- Attempting to update existing repo')
+    args = ['git', 'pull', '--rebase', 'origin', 'master']
+    subprocess.check_call(args, cwd=checkout_dir)
+
+
+def BuildClang(out_dir):
+  """Build clang from llvm repo at |GetCheckoutDir(out_dir)|."""
+  # Make <checkout>/build directory
+  build_dir = GetBuildDir(out_dir)
+  try:
+    os.mkdir(build_dir)
+  except OSError as e:
+    # Ignore errno 17 'File Exists'
+    if e.errno != 17:
+      raise e
+
+  # From that dir, run cmake
+  cmake_args = [
+      'cmake',
+      '-GNinja',
+      '-DLLVM_ENABLE_PROJECTS=clang;clang-tools-extra',
+      '-DCMAKE_BUILD_TYPE=Release',
+      '../llvm',
+  ]
+  subprocess.check_call(cmake_args, cwd=build_dir)
+
+  ninja_args = [
+      'ninja',
+      'clang-tidy',
+      'clang-apply-replacements',
+  ]
+  subprocess.check_call(ninja_args, cwd=build_dir)
+
+
+def BuildNinjaTarget(out_dir, ninja_target):
+  args = ['ninja', '-C', out_dir, ninja_target]
+  subprocess.check_call(args)
+
+
+def GenerateCompDb(out_dir):
+  gen_compdb_script = os.path.join(
+      os.path.dirname(__file__), 'generate_compdb.py')
+  comp_db_file = os.path.join(out_dir, 'compile_commands.json')
+  args = [gen_compdb_script, '-p', out_dir, '-o', comp_db_file]
+  subprocess.check_call(args)
+
+
+def RunClangTidy(checks, header_filter, auto_fix, out_dir, ninja_target):
+  """Invoke the |clang-tidy| binary."""
+  run_clang_tidy_script = os.path.join(
+      GetCheckoutDir(out_dir), 'clang-tools-extra', 'clang-tidy', 'tool',
+      'run-clang-tidy.py')
+
+  clang_tidy_binary = os.path.join(GetBuildDir(out_dir), 'bin', 'clang-tidy')
+  clang_apply_rep_binary = os.path.join(
+      GetBuildDir(out_dir), 'bin', 'clang-apply-replacements')
+
+  args = [
+      run_clang_tidy_script,
+      '-quiet',
+      '-p',
+      out_dir,
+      '-clang-tidy-binary',
+      clang_tidy_binary,
+      '-clang-apply-replacements-binary',
+      clang_apply_rep_binary,
+  ]
+
+  if checks:
+    args.append('-checks={}'.format(checks))
+
+  if header_filter:
+    args.append('-header-filter={}'.format(header_filter))
+
+  if auto_fix:
+    args.append('-fix')
+
+  args.append(ninja_target)
+  subprocess.check_call(args)
+
+
+def main():
+  script_name = sys.argv[0]
+
+  parser = argparse.ArgumentParser(
+      formatter_class=argparse.RawDescriptionHelpFormatter, epilog=__doc__)
+  parser.add_argument(
+      '--fetch', action='store_true', help='Fetch and build clang sources')
+  parser.add_argument(
+      '--build',
+      action='store_true',
+      help='build clang sources to get clang-tidy')
+  parser.add_argument('--checks', help='passed to clang-tidy')
+  parser.add_argument('--header-filter', help='passed to clang-tidy')
+  parser.add_argument(
+      '--auto-fix',
+      action='store_true',
+      help='tell clang-tidy to auto-fix errors')
+  parser.add_argument('OUT_DIR', help='where we are building Chrome')
+  parser.add_argument('NINJA_TARGET', help='ninja target')
+  args = parser.parse_args()
+
+  steps = []
+
+  if args.fetch:
+    steps.append(('Fetching clang sources', lambda: FetchClang(args.OUT_DIR)))
+
+  if args.build:
+    steps.append(('Building clang', lambda: BuildClang(args.OUT_DIR)))
+
+  steps += [
+      ('Building ninja target: %s' % args.NINJA_TARGET,
+       lambda: BuildNinjaTarget(args.OUT_DIR, args.NINJA_TARGET)),
+      ('Generating compilation DB', lambda: GenerateCompDb(args.OUT_DIR)),
+      ('Running clang-tidy',
+       lambda: RunClangTidy(args.checks, args.header_filter, args.auto_fix, args
+                            .OUT_DIR, args.NINJA_TARGET)),
+  ]
+
+  # Run the steps in sequence.
+  for i, (msg, step_func) in enumerate(steps):
+    # Print progress message
+    print '-- %s %s' % (script_name, '-' * (80 - len(script_name) - 4))
+    print '-- [%d/%d] %s' % (i + 1, len(steps), msg)
+    print 80 * '-'
+
+    step_func()
+
+  return 0
+
+
+if __name__ == '__main__':
+  sys.exit(main())