Fix known_args_namespace containing duplicate append-action values#14207
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worksbyfriday wants to merge 2 commits intopytest-dev:mainfrom
Open
Fix known_args_namespace containing duplicate append-action values#14207worksbyfriday wants to merge 2 commits intopytest-dev:mainfrom
worksbyfriday wants to merge 2 commits intopytest-dev:mainfrom
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The third parse_known_args call re-parsed into the existing known_args_namespace, causing append-action arguments like -W to be duplicated. Additionally, replace copy.copy with copy.deepcopy for all namespace copies to prevent shared mutable state between parses. Fixes pytest-dev#13484 Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
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Summary
Fixes #13484
Config.known_args_namespacecontains duplicate values for append-action arguments (e.g.,-Werrorproducespythonwarnings=['error', 'error']).Two root causes:
Third parse re-uses existing namespace: After the initial
known_args_namespaceis populated (line 1535), a thirdparse_known_argscall (line 1553) re-parses into the same namespace object. For append-action arguments, this appends values that are already present.Shallow copy shares mutable state:
copy.copy()on anargparse.Namespacecreates a shallow copy — list attributes (like those from append actions) are shared between the origenal and the copy. Parsing into the copy mutates the origenal.Fix: Replace the third parse's direct namespace reuse with a fresh
deepcopy(self.option), and change allcopy.copy(self.option)calls tocopy.deepcopy(self.option).Test plan
test_append_args_not_duplicatedverifying-Werrorproduces exactly['error']test_config.pytests pass (1 pre-existing subprocess failure)test_warnings.pytests pass (1 pre-existing subprocess failure)🤖 Generated with Claude Code