build/assembly/scripts/compare_json_list.py

#!/usr/bin/env python3.8
# Copyright 2022 The Fuchsia Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

import argparse
import json
import sys


# Removes |prefix| from |line|.
# A removeprefix() function is not available until 3.9.
def removeprefix(line, prefix):
    if line.startswith(prefix):
        return line[len(prefix):]
    return line


# Create new dict/lists containers that are hashable, but first remove any
# |prefixes| from nested strings.
def make_hashable(item, prefixes):
    if isinstance(item, dict):
        item = hashabledict(item, prefixes)
    elif isinstance(item, list):
        item = hashablelist(item, prefixes)
    elif isinstance(item, str):
        for prefix in prefixes:
            item = removeprefix(item, prefix)
    return item


# A list that is hashable so it can be added to a set.
class hashablelist(list):

    def __init__(self, list, prefixes):
        for v in list:
            self.append(make_hashable(v, prefixes))

    def __hash__(self):
        return hash(tuple(sorted(self)))

    def __eq__(self, other):
        return sorted(self) == sorted(other)


# A dictionary that is hashable so it can be added to a set.
class hashabledict(dict):

    def __init__(self, dict, prefixes):
        for k, v in dict.items():
            self[k] = make_hashable(v, prefixes)

    def __hash__(self):
        return hash(tuple(sorted(self.items())))


# Loads a set of items from a json file and optionally, uses |key| to get the list.
# Any |prefixes| will be stripped from strings in each item.
def load_set_from_json(log, key, prefixes):
    items = json.load(log)
    if key:
        items = items.get(key, [])
    return set(make_hashable(i, prefixes) for i in items)


def main():
    parser = argparse.ArgumentParser(
        description=
        'Compare two json lists generated by different assembly invocations'
        'and assert that they are functionally equivalent')
    parser.add_argument(
        '--reference', type=argparse.FileType('r'), required=True)
    parser.add_argument(
        '--comparison', type=argparse.FileType('r'), required=True)
    parser.add_argument('--stamp', type=argparse.FileType('w'), required=True)
    parser.add_argument('--strip-prefix', nargs='*')
    parser.add_argument('--list-key', type=str)
    args = parser.parse_args()

    reference = load_set_from_json(
        args.reference, args.list_key, args.strip_prefix)
    comparison = load_set_from_json(
        args.comparison, args.list_key, args.strip_prefix)

    # Checks for missing commands.
    missing = reference.difference(comparison)
    extra = comparison.difference(reference)
    if missing:
        print('Items in the reference were missing from the comparison')
        for cmd in missing:
            print('Missing: ' + str(cmd))
    if extra:
        print('Items in the comparison were not found in the reference')
        for cmd in extra:
            print('Extra: ' + str(cmd))
    if missing or extra:
        return len(missing) + len(extra)

    # Writes an empty file because GN requires targets to have an output.
    args.stamp.write("")

    return 0


if __name__ == '__main__':
    sys.exit(main())