Include flag_check hook for "packages/SystemUI"

Parse arguments in flag_check.py.

- msg = commit message
- files = modified files paths
- project = repo_path

Using project we can filter further for "frameworks/base" and see if
files starts with "packages/SystemUI" and then apply Flags check.

Bug: 306262821
Test: Manual
Flag: NA
Change-Id: I9b678344512527ec8b79aa458dae9f54fb4c61ba

PREUPLOAD.cfg

@@ -28,3 +28,6 @@ hidden_api_txt_exclude_hook = ${REPO_ROOT}/frameworks/base/tools/hiddenapi/exclu
 ktfmt_hook = ${REPO_ROOT}/external/ktfmt/ktfmt.py --check -i ${REPO_ROOT}/frameworks/base/ktfmt_includes.txt ${PREUPLOAD_FILES}
 
 ktlint_hook = ${REPO_ROOT}/prebuilts/ktlint/ktlint.py --no-verify-format -f ${PREUPLOAD_FILES}
+
+# This flag check hook runs only for "packages/SystemUI" subdirectory. If you want to include this check for other subdirectories, please modify flag_check.py.
+flag_hook = ${REPO_ROOT}/frameworks/base/packages/SystemUI/flag_check.py --msg=${PREUPLOAD_COMMIT_MESSAGE} --files=${PREUPLOAD_FILES} --project=${REPO_PATH}

packages/SystemUI/flag_check.py

@@ -0,0 +1,134 @@
+#! /usr/bin/env python3
+
+import sys
+import re
+import argparse
+
+# partially copied from tools/repohooks/rh/hooks.py
+
+TEST_MSG = """Commit message is missing a "Flag:" line.  It must match one of the
+following case-sensitive regex:
+
+    %s
+
+The Flag: stanza is regex matched and should describe whether your change is behind a flag or flags.
+
+As a CL author, you'll have a consistent place to describe the risk of the proposed change by explicitly calling out the name of the
+flag in addition to its state (ENABLED|DISABLED|DEVELOPMENT|TEAMFOOD|TRUNKFOOD|NEXTFOOD).
+
+Some examples below:
+
+Flag: NONE
+Flag: NA
+Flag: LEGACY ENABLE_ONE_SEARCH DISABLED
+Flag: ACONFIG com.android.launcher3.enable_twoline_allapps DEVELOPMENT
+Flag: ACONFIG com.android.launcher3.enable_twoline_allapps TRUNKFOOD
+
+Check the git history for more examples. It's a regex matched field.
+"""
+
+def main():
+    """Check the commit message for a 'Flag:' line."""
+    parser = argparse.ArgumentParser(
+        description='Check the commit message for a Flag: line.')
+    parser.add_argument('--msg',
+                        metavar='msg',
+                        type=str,
+                        nargs='?',
+                        default='HEAD',
+                        help='commit message to process.')
+    parser.add_argument(
+        '--files',
+        metavar='files',
+        nargs='?',
+        default='',
+        help=
+        'PREUPLOAD_FILES in repo upload to determine whether the check should run for the files.')
+    parser.add_argument(
+        '--project',
+        metavar='project',
+        type=str,
+        nargs='?',
+        default='',
+        help=
+        'REPO_PATH in repo upload to determine whether the check should run for this project.')
+
+    # Parse the arguments
+    args = parser.parse_args()
+    desc = args.msg
+    files = args.files
+    project = args.project
+
+    if not should_run_path(project, files):
+        return
+
+    field = 'Flag'
+    none = '(NONE|NA|N\/A)' # NONE|NA|N/A
+
+    typeExpression = '\s*(LEGACY|ACONFIG)' # [type:LEGACY|ACONFIG]
+
+    # legacyFlagName contains only uppercase alphabets with '_' - Ex: ENABLE_ONE_SEARCH
+    # Aconfig Flag name format = "packageName"."flagName"
+    # package name - Contains only lowercase alphabets + digits + '.' - Ex: com.android.launcher3
+    # For now alphabets, digits, "_", "." characters are allowed in flag name and not adding stricter format check.
+    #common_typos_disable
+    flagName = '([a-zA-z0-9_.])+'
+
+    #[state:ENABLED|DISABLED|DEVELOPMENT|TEAM*(TEAMFOOD)|TRUNK*(TRUNK_STAGING, TRUNK_FOOD)|NEXT*(NEXTFOOD)]
+    stateExpression = '\s*(ENABLED|DISABLED|DEVELOPMENT|TEAM[a-zA-z]*|TRUNK[a-zA-z]*|NEXT[a-zA-z]*)'
+    #common_typos_enable
+
+    readableRegexMsg = '\n\tFlag: (NONE|NA)\n\tFlag: LEGACY|ACONFIG FlagName|packageName.flagName ENABLED|DISABLED|DEVELOPMENT|TEAMFOOD|TRUNKFOOD|NEXTFOOD'
+
+    flagRegex = fr'^{field}: .*$'
+    check_flag = re.compile(flagRegex) #Flag:
+
+    # Ignore case for flag name format.
+    flagNameRegex = fr'(?i)^{field}:\s*({none}|{typeExpression}\s*{flagName}\s*{stateExpression})\s*'
+    check_flagName = re.compile(flagNameRegex) #Flag: <flag name format>
+
+    flagError = False
+    foundFlag = []
+    # Check for multiple "Flag:" lines and all lines should match this format
+    for line in desc.splitlines():
+        if check_flag.match(line):
+            if not check_flagName.match(line):
+                flagError = True
+                break
+            foundFlag.append(line)
+
+    # Throw error if
+    # 1. No "Flag:" line is found
+    # 2. "Flag:" doesn't follow right format.
+    if (not foundFlag) or (flagError):
+        error = TEST_MSG % (readableRegexMsg)
+        print(error)
+        sys.exit(1)
+
+    sys.exit(0)
+
+
+def should_run_path(path, files):
+    """Returns a boolean if this check should run with these paths.
+    If you want to check for a particular subdirectory under the path,
+    add a check here, call should_run_files and check for a specific sub dir path in should_run_files.
+    """
+    if not path:
+        return False
+    if path == 'frameworks/base':
+        return should_run_files(files)
+    # Default case, run for all other paths which calls this script.
+    return True
+
+
+def should_run_files(files):
+    """Returns a boolean if this check should run with these files."""
+    if not files:
+        return False
+    if 'packages/SystemUI' in files:
+        return True
+    return False
+
+
+if __name__ == '__main__':
+    main()