fix(openapi): preserve 204 status code in response conversion

[devin-ai-integration]

Description

Fixes a bug where a 204 No Content status code defined in an OpenAPI spec is displayed as "200 Successful" in Fern docs. The status code was being lost during the OpenAPI → Fern IR conversion because no-body responses produced undefined in the response field, and downstream defaults filled in 200.

This also affects other non-200 success codes (201, 202) when the endpoint has no response body.

Changes Made

Three files in the OpenAPI importer pipeline are modified:

1. convertResponse.ts — Added a successStatusCode field to ConvertedResponse that tracks the first success status code encountered, even when the response has no body (i.e., value is undefined).

2. convertHttpOperation.ts — When convertedResponse.value is undefined but successStatusCode is non-200, creates a ResponseWithExample.text() carrier to propagate the status code through the IR.

3. buildEndpoint.ts — In the text response handler, special-cases statusCode === 204 to emit only "status-code": 204 in the Fern Definition without setting type: "text", so the downstream IR correctly represents a no-body response.

Additionally:

• Added a no-content seed test fixture (test-definitions/fern/apis/no-content/) with an OpenAPI spec containing a DELETE endpoint returning 204
• Generated ts-sdk seed output for the new fixture
• Added an unreleased changelog entry
• Updated snapshots across multiple test suites (openapi-ir-to-fern-tests, v3-importer-tests, ir-to-jsonschema, ete-tests)

⚠️ Reviewer Checklist

• Carrier response approach: The fix uses ResponseWithExample.text() as a "carrier" to thread the status code through the OpenAPI IR (which doesn't have a dedicated "no body" response variant). Confirm this doesn't cause unexpected behavior in other consumers of the IR.
• Hardcoded 204 in buildEndpoint.ts: The textResponse.statusCode === 204 check is specific to 204. Other non-200 codes with no body (e.g., 201) will still get type: "text" set in the Fern Definition. Consider whether this should be more general (e.g., checking for absence of actual text content). The ete-test snapshots show this: petstore's createPets (201) now gets status-code: 201 with type: text, while 204 endpoints get only status-code: 204.
• Snapshot changes: Examples are removed from endpoints that now have carrier text responses (e.g., hathora's delete/destroy/suspend endpoints, file-upload's create conversation). Verify this is acceptable behavior.
• Downstream pipeline: This fix ensures status code reaches the Fern IR, but fern-platform's v1ToV2.ts migrator also has statusCode ?? 200 and an early return undefined when response.type == null. A separate fix there may be needed for full end-to-end correctness after re-running fern generate --docs.
• Other generators: Only ts-sdk seed output was generated. Verify whether other generators also need seed output for this fixture.

Testing

• Seed test (ts-sdk) passes for the new no-content fixture
• pnpm compile passes for affected packages
• pnpm run check (biome) passes cleanly
• All CI checks pass (260/260)

Link to Devin session: https://app.devin.ai/sessions/59b2594a5ea74b39bdd202e1e2eb5eee

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[devin-ai-integration]

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SDK Generation Benchmark Results

Comparing PR branch against latest nightly baseline on main (2026-04-14T04:55:49Z).

Full benchmark table (click to expand)

Generator	Spec	main (generator)	main (E2E)	PR (generator)	Delta
csharp-sdk	square	92s	127s	86s	-6s (-6.5%)
go-sdk	square	90s	137s	107s	+17s (+18.9%)
java-sdk	square	173s	187s	168s	-5s (-2.9%)
php-sdk	square	84s	122s	85s	+1s (+1.2%)
python-sdk	square	128s	163s	128s	+0s (+0.0%)
ruby-sdk-v2	square	113s	156s	133s	+20s (+17.7%)
rust-sdk	square	96s	92s	100s	+4s (+4.2%)
swift-sdk	square	86s	129s	84s	-2s (-2.3%)
ts-sdk	square	101s	136s	96s	-5s (-5.0%)

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: 2026-04-14T04:55:49Z). Trigger benchmark-baseline to refresh.
Last updated: 2026-04-14 16:59 UTC