fix(python): derive offset pagination _has_next instead of hardcoding True

[patrickthornton]

Closes FER-10931.

Summary

The Python SDK generator's offset paginator hardcoded _has_next = True for every generated list endpoint, which caused a couple problems: while pager.has_next: pager = pager.next_page() never terminated; for x in pager worked only because the core paginator stops when get_next() returns an empty page.

It also ignored the IR's optional OffsetPagination.has_next_page response property, so users who explicitly declared has-next-page: $response.<field> still got the hardcoded True.

Reported by a customer using offset pagination via x-fern-pagination: { offset: $request.page, results: $response.data }.

Change

init_has_next() in generators/python/.../pagination/offset.py now:

def init_has_next(self) -> str:
    if self.offset.has_next_page is not None:
        path = self._response_property_to_dot_access(self.offset.has_next_page)
        return f"bool({Paginator.PARSED_RESPONSE_VARIABLE}.{path})"
    return f"len({Paginator.PAGINATION_ITEMS_VARIABLE} or []) > 0"

Items-length fallback matches the TypeScript generator's hasNextPage: (r) => (r?.data ?? []).length > 0.

Before / after (generated)

 _items = _parsed_response.data.users if _parsed_response.data is not None else []
-_has_next = True
+_has_next = len(_items or []) > 0
 _get_next = lambda: self.list_with_offset_pagination(page=page + 1, ...)

And for endpoints that explicitly declare has-next-page: $response.hasNextPage:

-_has_next = True
+_has_next = bool(_parsed_response.has_next_page)

Test plan

• pnpm seed test --generator python-sdk --fixture pagination --skip-scripts --local regenerated all 3 offset-pagination fixtures; snapshots updated in this PR.
• Confirmed no remaining _has_next = True strings in seed/python-sdk/.
• CI seed run.

[claude]

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SDK Generation Benchmark Results

Comparing PR branch against median of 5 nightly run(s) on main (latest: 2026-06-01T05:35:53Z).

Full benchmark table (click to expand)

Generator	Spec	main (generator)	main (E2E)	PR (generator)	Delta
python-sdk	square	137s (n=5)	236s (n=5)	139s	+2s (+1.5%)

main (generator): generator-only time via --skip-scripts (includes Docker image build, container startup, IR parsing, and code generation — this is the same Docker-based flow customers use via fern generate). main (E2E): full customer-observable time including build/test scripts (nightly baseline, informational). Delta is computed against generator-only baseline.
⚠️ = generation exited with a non-zero exit code (timing may not reflect a successful run).
Baseline from nightly runs on main (latest: 2026-06-01T05:35:53Z). Trigger benchmark-baseline to refresh.
Last updated: 2026-06-01 18:22 UTC