skymarshal: only parse argfiles for the first argument

We want to pass some arguments to skymarshal that start with @. argparse was
trying to expand these as if they were argfiles. Here we switch to only
trying to interpret the first argument as an argfile, which should be all
that's necessary.

Topic: skymarshal-narrow-argfile
GitOrigin-RevId: 3d93c30e0565d7515acf7036e029c774d2bd32ff

third_party/skymarshal/skymarshal/skymarshal.py

@@ -7,6 +7,8 @@
 
 import argparse
 import os
+import shlex
+import sys
 import typing as T
 
 import six
@@ -17,7 +19,7 @@
 def parse_args(languages, args=None):
     # type: (T.Sequence[T.Type[SkymarshalLanguage]], T.Optional[T.Sequence[str]]) -> argparse.Namespace
     """Parse the argument list and return an options object."""
-    parser = argparse.ArgumentParser(description=__doc__, fromfile_prefix_chars="@")
+    parser = argparse.ArgumentParser(description=__doc__)
     parser.add_argument("source_path", nargs="+")
     parser.add_argument("--debug-tokens", action="store_true")
     parser.add_argument("--print-def", action="store_true")
@@ -43,7 +45,17 @@ def parse_args(languages, args=None):
         options = parser.parse_args(args)
     else:
         # Use the command-line args.
-        options = parser.parse_args()
+
+        # NOTE(will): Support argfiles, e.g. @argfile as the first argument. argparse supports this
+        # directly with fromfile_prefix_chars="@", but this was causing issues for any arguments
+        # that started with @, even if those arguments were inside the argfile. This approach is
+        # much narrower in only supporting an argfile as the first argument.
+        if len(sys.argv) >= 2 and sys.argv[1].startswith("@"):
+            with open(sys.argv[1][1:]) as argfile:
+                args = shlex.split(argfile.read())
+            options = parser.parse_args(args + sys.argv[2:])
+        else:
+            options = parser.parse_args()
 
     return options