fix(openapi-fetch): use text() when no content-length is provided to avoid errors parsing empty response (200 with no content)

[srbarba]

Changes

Fixes an issue where responses with HTTP 200 status and no Content-Length header would fail when parsing JSON, even when the response body is empty.

Problem: When a server returns a successful response (200 OK) without a Content-Length header and an empty body, calling response.json() directly throws an error because there's no content to parse. This is a valid HTTP scenario but was causing runtime errors.

Solution: Added a check for missing Content-Length headers when parseAs: "json". The fix:

1. First reads the response as text using response.text()
2. Then conditionally parses it as JSON only if content exists
3. Returns undefined if the response is empty

How to Review

1. Review the logic: Check the added condition in index.js around line 245 that handles the case when parseAs === "json" && !contentLength
2. Run the test: The new test "json with empty response" in response.test.ts verifies the fix works correctly
3. Verify no regressions: All existing tests should pass, confirming backward compatibility
4. Consider edge cases: The fix only applies when:
   • Response is successful (2** except 204)
   • parseAs is set to "json" (default)
   • Content-Length header is absent (not just "0")

Key review points:

• Empty responses now return { data: undefined } instead of throwing an error
• Responses with Content-Length: "<any>" are still handled by the existing logic
• The fix doesn't affect error responses or other parseAs options

Checklist

• Unit tests updated
• docs/ updated (if necessary) - No docs changes needed, internal bug fix
• pnpm run update:examples run (only applicable for openapi-typescript) - N/A, this is openapi-fetch

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[changeset-bot]

🦋 Changeset detected

Latest commit: a38257a

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 3 packages

Name	Type
openapi-fetch	Patch
openapi-react-query	Patch
swr-openapi	Patch

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[srbarba]

Related issue: #1977

[drwpow]

Makes sense. Good tests, thank you!