Add Python style checker to system/bt

* Based on Google style and ensure 4 spaces are used for indentation
* http://google.github.io/styleguide/pyguide.html

Bug: 146016811
Test: upload CLs
Change-Id: I27b9232d59e9e9bd59ca1414ef6f9db85c41a808

3 files changed, 94 insertions, 0 deletions

diff --git a/.style.yapf b/.style.yapf
new file mode 100644
index 000000000..3c8af88e1
--- /dev/null
+++ b/.style.yapf
@@ -0,0 +1,4 @@
+[style]
+# http://google.github.io/styleguide/pyguide.html
+based_on_style: google
+indent_width: 4
diff --git a/PREUPLOAD.cfg b/PREUPLOAD.cfg
index 380216c21..a4730406c 100644
--- a/PREUPLOAD.cfg
+++ b/PREUPLOAD.cfg
@@ -6,4 +6,5 @@ clang_format = true
 
 [Hook Scripts]
 aosp_first = ${REPO_ROOT}/frameworks/base/tools/aosp/aosp_sha.sh ${PREUPLOAD_COMMIT} ".*$"
+yapf_hook = ./tools/scripts/yapf_checker.py
 
diff --git a/tools/scripts/yapf_checker.py b/tools/scripts/yapf_checker.py
new file mode 100755
index 000000000..86f1f3963
--- /dev/null
+++ b/tools/scripts/yapf_checker.py
@@ -0,0 +1,89 @@
+#!/usr/bin/env python3
+#
+#   Copyright 2019 - The Android Open Source Project
+#
+#   Licensed under the Apache License, Version 2.0 (the "License");
+#   you may not use this file except in compliance with the License.
+#   You may obtain a copy of the License at
+#
+#       http://www.apache.org/licenses/LICENSE-2.0
+#
+#   Unless required by applicable law or agreed to in writing, software
+#   distributed under the License is distributed on an "AS IS" BASIS,
+#   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#   See the License for the specific language governing permissions and
+#   limitations under the License.
+
+import logging
+import os
+import subprocess
+import sys
+
+PYTHONPATH_KEY = 'PYTHONPATH'
+COMMIT_ID_ENV_KEY = 'PREUPLOAD_COMMIT'
+ANDROID_BUILD_TOP_KEY = 'ANDROID_BUILD_TOP'
+DEFAULT_YAPF_DIR = 'external/yapf'
+GIT_COMMAND = ['git', 'diff-tree', '--no-commit-id', '--name-only']
+
+
+def main():
+    """
+    A Python commit formatter using YAPF
+
+    Caveat: if you modify a file, the entire file will be formatted, instead of
+            the diff
+    :return:
+    """
+    if COMMIT_ID_ENV_KEY not in os.environ:
+        logging.error('Missing PREUPLOAD_COMMIT in environment.')
+        exit(1)
+
+    if ANDROID_BUILD_TOP_KEY not in os.environ:
+        logging.error('Missing ANDROID_BUILD_TOP in environment.')
+        exit(1)
+
+    # Gather changed Python files
+    commit_id = os.environ[COMMIT_ID_ENV_KEY]
+    full_git_command = GIT_COMMAND + ['-r', commit_id]
+    files = subprocess.check_output(full_git_command).decode(
+        'utf-8').splitlines()
+    full_files = [os.path.abspath(f) for f in files if f.endswith('.py')]
+    if not full_files:
+        return
+
+    # Find yapf in Android code tree
+    yapf_dir = os.path.join(os.environ[ANDROID_BUILD_TOP_KEY], DEFAULT_YAPF_DIR)
+    yapf_binary = os.path.join(yapf_dir, 'yapf')
+
+    # Run YAPF
+    full_yapf_command = [
+        "%s=$%s:%s" % (PYTHONPATH_KEY, PYTHONPATH_KEY, yapf_dir), 'python3',
+        yapf_binary, '-d', '-p'
+    ] + full_files
+    environment = os.environ.copy()
+    environment[PYTHONPATH_KEY] = environment[PYTHONPATH_KEY] + ":" + yapf_dir
+    result = subprocess.run(
+        full_yapf_command[1:],
+        env=environment,
+        stderr=subprocess.STDOUT,
+        stdout=subprocess.PIPE)
+
+    if result.returncode != 0 or result.stdout:
+        logging.error(result.stdout.decode('utf-8').strip())
+        logging.error('INVALID FORMATTING, return code %d', result.returncode)
+        logging.error('To re-run the format command:\n\n'
+                      '    %s\n' % ' '.join(full_yapf_command))
+        yapf_inplace_format = ' '.join([
+            "%s=$%s:%s" % (PYTHONPATH_KEY, PYTHONPATH_KEY,
+                           yapf_dir), 'python3', yapf_binary, '-p', '-i'
+        ] + full_files)
+        logging.error('If this is a legitimate format error, please run:\n\n'
+                      '    %s\n' % yapf_inplace_format)
+        logging.error(
+            'CAVEAT: Currently, this format the entire Python file if you modify even part of it'
+        )
+        exit(1)
+
+
+if __name__ == '__main__':
+    main()