fix: parse_response crashes on null output from Codex backend stream

[thiagobarbosa]

Fix #3313

Fix a crash in parse_response when a Response from the Codex backend stream has a null (None) output field instead of a list.

Before this fix, any consumer receiving a Response with a null output (observed from the Codex backend stream) would hit a TypeError: 'NoneType' object is not iterable inside parse_response. The fix treats a missing/None output the same as an empty list, matching how other optional list fields are typically handled in this SDK.

• src/openai/lib/_parsing/_responses.py: iterate over response.output or [] instead of response.output, so a None output no longer raises a TypeError and is treated as an empty output list. This file lives under src/openai/lib/, which per CONTRIBUTING.md is excluded from code generation, so it's safe to edit by hand.
• tests/lib/responses/test_responses.py: add test_parse_response_handles_null_output, which constructs a Response with output=None and asserts parse_response(...) returns parsed.output == [] instead of raising.

[Copilot]

Pull request overview

Fixes a TypeError in parse_response() when the Codex backend stream returns a Response with output: null by treating None output as an empty list, and adds regression test coverage for that case.

Changes:

• Guard parse_response() against response.output is None by iterating over response.output or [].
• Add a unit test asserting output=None is parsed as [] without raising.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
src/openai/lib/_parsing/_responses.py	Prevents iteration over None by defaulting missing/None output to an empty list.
tests/lib/responses/test_responses.py	Adds a regression test to ensure parse_response() handles output=None and returns parsed.output == [].

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[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 1 comment.

[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated 2 comments.