Serialize arguments via json on restart.

We want to ignore some positional arguments without ignoring flags/values - and
since there's no easy way to "unparse" an argparse namespace, we instead pass
it as json.

Also note we can't pass it as a file easily, as args have to be available very
early. Passing it as an argument shouldn't be an issue though.

qutebrowser/app.py

@@ -31,6 +31,7 @@ import functools
 import traceback
 import faulthandler
 import datetime
+import json
 
 from PyQt5.QtWidgets import QApplication, QDialog, QMessageBox
 from PyQt5.QtGui import QDesktopServices, QPixmap, QIcon
@@ -683,19 +684,28 @@ class Application(QApplication):
                 # cwd=None and see if that works out.
                 # See https://github.com/The-Compiler/qutebrowser/issues/323
                 cwd = None
-        for arg in sys.argv[1:]:
-            if arg.startswith('-'):
-                # We only want to preserve options on a restart.
-                args.append(arg)
+
         # Add all open pages so they get reopened.
         page_args = []
         for win in pages:
             page_args.extend(win)
             page_args.append('')
-        if page_args:
-            args.extend(page_args[:-1])
+
+        # Serialize the argparse namespace into json and pass that to the new
+        # process via --json-args.
+        # We do this as there's no way to "unparse" the namespace while
+        # ignoring some arguments.
+        argdict = vars(self._args)
+        argdict['session'] = None
+        argdict['url'] = []
+        argdict['command'] = page_args[:-1]
+        argdict['json_args'] = None
+        data = json.dumps(argdict)
+        args += ['--json-args', data]
+
         log.destroy.debug("args: {}".format(args))
         log.destroy.debug("cwd: {}".format(cwd))
+
         return args, cwd
 
     @cmdutils.register(instance='app', ignore_args=True)

qutebrowser/qutebrowser.py

@@ -20,6 +20,7 @@
 """Early initialization and main entry point."""
 
 import sys
+import json
 
 import qutebrowser
 try:
@@ -58,6 +59,7 @@ def get_argparser():
     parser.add_argument('-R', '--override-restore', help="Don't restore a "
                         "session even if one would be restored.",
                         action='store_true')
+    parser.add_argument('--json-args', help=argparse.SUPPRESS)
 
     debug = parser.add_argument_group('debug arguments')
     debug.add_argument('-l', '--loglevel', dest='loglevel',
@@ -118,6 +120,13 @@ def main():
     """Main entry point for qutebrowser."""
     parser = get_argparser()
     args = parser.parse_args()
+    if args.json_args is not None:
+        # Restoring after a restart.
+        # When restarting, we serialize the argparse namespace into json, and
+        # construct a "fake" argparse.Namespace here based on the data loaded
+        # from json.
+        data = json.loads(args.json_args)
+        args = argparse.Namespace(**data)
     earlyinit.earlyinit(args)
     # We do this imports late as earlyinit needs to be run first (because of
     # the harfbuzz fix and version checking).