Issue 6945 - Add script to make filter list diffs

abp/filters/diff_script.py

+# This file is part of Adblock Plus <https://adblockplus.org/>,
+# Copyright (C) 2006-present eyeo GmbH
+#
+# Adblock Plus is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License version 3 as
+# published by the Free Software Foundation.
+#
+# Adblock Plus is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with Adblock Plus.  If not, see <http://www.gnu.org/licenses/>.
+
+"""Command line script for rendering Adblock Plus filter list diffs."""
+
+from __future__ import print_function
+
+import argparse
+import io
+import sys
+
+from .renderer import render_diff
+
+__all__ = ['main']
+
+
+def parse_args():
+    parser = argparse.ArgumentParser(description='Render a filter list diff.')
+    parser.add_argument(
+        'base', help='the older filter list that needs to be updated',
+        nargs='?')

[Sebastian Noack, 2018/09/24 22:21:09]

Didn't we want to make those arguments mandatory?

[rhowell, 2018/09/25 01:53:45]

Positional arguments are already mandatory (or it will raise a TypeError).
Vasily's suggestion was to remove the `default='-'` arguments. I did that in
patch set 3.

[Sebastian Noack, 2018/09/25 17:00:39]

I see, the documentation seems a little misleading:

  One argument will be consumed from the command line if possible, and
  produced as a single item. If no command-line argument is present,
  the value from default will be produced.

It doesn't specify what happens if no default is specified. I wonder what would
happen if you omit the nargs argument altogether?

+    parser.add_argument(
+        'latest', help='the most recent version of the filter list',
+        nargs='?')
+    parser.add_argument(
+        'outfile', help='output file for filter list diff',
+        default='-', nargs='?')
+    return parser.parse_args()
+
+
+def main():
+    """Entry point for the diff rendering script (diffrender)."""
+    args = parse_args()
+
+    with io.open(args.base, 'r', encoding='utf-8') as base, \
+            io.open(args.latest, 'r', encoding='utf-8') as latest:
+
+        lines = render_diff(base, latest)
+        if args.outfile == '-':
+            outfile = io.open(sys.stdout.fileno(), 'w',
+                              closefd=False,
+                              encoding=sys.stdout.encoding or 'utf-8')
+        else:
+            outfile = io.open(args.outfile, 'w', encoding='utf-8')
+
+        with outfile:
+            for line in lines:
+                print(line, file=outfile)