comparators: add 'asar' support

diffoscope/comparators/__init__.py

@@ -125,6 +125,7 @@ class ComparatorManager:
         ("vmlinuz.VmlinuzFile",),
         ("arsc.ArscFile",),
         ("xar.XarFile",),
+        ("asar.AsarFile",),
     )
 
     _singleton = {}

diffoscope/comparators/asar.py

+#
+# diffoscope: in-depth comparison of files, archives, and directories
+#
+# Copyright © 2014-2015 Jérémy Bobbio <lunar@debian.org>
+# Copyright © 2015-2020 Chris Lamb <lamby@debian.org>
+#
+# diffoscope is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# diffoscope 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 diffoscope.  If not, see <https://www.gnu.org/licenses/>.
+
+import os
+import re
+import logging
+import subprocess
+
+from diffoscope.tools import tool_required
+from diffoscope.tempfiles import get_temporary_directory
+
+from .utils.file import File
+from .utils.archive import Archive
+from .utils.command import our_check_output
+
+logger = logging.getLogger(__name__)
+
+
+class AsarContainer(Archive):
+    @tool_required("asar")
+    def open_archive(self):
+        # Just extract the asar as a whole due to the problems mentioned below
+        self._members = []
+        self._unpacked = get_temporary_directory(suffix="asar")
+
+        logger.debug("Extracting asar to %s", self._unpacked.name)
+
+        our_check_output(
+            [
+                "asar",
+                "extract",
+                os.path.abspath(self.source.path),
+                self._unpacked.name,
+            ],
+            cwd=self._unpacked.name,
+        )
+
+        for root, _, files in os.walk(self._unpacked.name):
+            current_dir = []
+
+            for filename in sorted(files):
+                abspath = os.path.join(root, filename)
+
+                relpath = abspath[len(self._unpacked.name) + 1 :]
+
+                current_dir.append(relpath)
+
+            self._members.extend(current_dir)
+
+        return self
+
+    def close_archive(self):
+        self._unpacked.cleanup()
+
+    def get_member_names(self):
+        # 'asar list' returns all entries including directories, so it's hard to use
+        # rely on extraction to temp directory instead
+        return self._members
+
+    def extract(self, member_name, dest_dir):
+        # while 'asar' lets us extract single files, it does not let us specify where to output them at all.
+        # rely on extraction to temp directory instead
+        return os.path.join(self._unpacked.name, member_name)
+
+
+class AsarFile(File):
+    DESCRIPTION = "asar archives"
+    CONTAINER_CLASSES = [AsarContainer]
+    FILE_TYPE_RE = re.compile(r"^\bElectron ASAR archive\b")