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fix(responseInterceptor): handle bodyless responses (HEAD/1xx/204/304) with content-encoding#1251

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chimurai merged 1 commit into
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fix-responseInterceptor-bodyless-decompression-error
May 25, 2026
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fix(responseInterceptor): handle bodyless responses (HEAD/1xx/204/304) with content-encoding#1251
chimurai merged 1 commit into
masterfrom
fix-responseInterceptor-bodyless-decompression-error

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@chimurai

@chimurai chimurai commented May 25, 2026 •
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fixes: #381
fixes: #658

reproduction:

const targetServer = http.createServer((req, res) => {
  res.statusCode = 204;
  res.setHeader('content-type', 'application/json; charset=utf-8');
  res.setHeader('content-encoding', 'gzip');
  res.end();
});


const app = express();
app.use(
  '/abc',
  createProxyMiddleware({
    target: targetUrl,
    changeOrigin: true,
    selfHandleResponse: true,
    on: {
      proxyRes: responseInterceptor(async (buffer) => buffer),
    },
  }),
);

response:

{
  "status": 200,
  "text": "Error fetching proxied request: unexpected end of file",
  "body": {},
  "headers": {
    "x-powered-by": "Express",
    "date": "Mon, 25 May 2026 10:45:02 GMT",
    "connection": "close",
    "content-length": "54"
  }
}

also mentioned in:

Summary by CodeRabbit

  • Bug Fixes

    • Fixed handling of bodyless HTTP responses (HEAD, 1xx, 204, 304) when upstream includes content-encoding headers. The response interceptor now correctly removes content-encoding from proxied response headers for these cases.

  • Tests

    • Added test coverage for bodyless responses with content-encoding headers.

Review Change Stack

@coderabbitai

coderabbitai Bot commented May 25, 2026 •
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📝 Walkthrough

Walkthrough

The PR fixes a bug in responseInterceptor where bodyless HTTP responses (HEAD, 1xx, 204, 304) with content-encoding headers caused decompression errors. The fix adds detection logic, skips content-encoding processing for bodyless responses, and exits early without writing a body. Tests validate the behavior across unit and e2e scopes.

Changes

Bodyless Response Handling

Layer / File(s) Summary
Bodyless response detection and interception fix
src/handlers/response-interceptor.ts, test/unit/response-interceptor.spec.ts		 Added isBodylessResponse() helper to identify HEAD requests and 1xx/204/304 responses. Integrated helper to skip content-encoding decompression and to end the response early (after headers, without invoking the interceptor). Unit tests verify HEAD and 103 responses bypass interception and body writing.
End-to-end validation for bodyless responses with content-encoding
test/e2e/response-interceptor.spec.ts		 E2E test suite validates 204 and 304 responses with upstream content-encoding (gzip/deflate) are returned bodyless, with content-encoding removed from proxy headers, and with other headers (cache-control, etag) preserved.
Documentation and configuration updates
CHANGELOG.md, cspell.json		 Changelog documents the fix for bodyless responses with content-encoding. Spellcheck dictionary includes "bodyless".

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

  • chimurai/http-proxy-middleware#1249: Both PRs modify src/handlers/response-interceptor.ts to adjust header filtering around content-encoding in similar code paths (main PR handles bodyless responses, related PR addresses trailer/transfer-encoding conflicts).
  • chimurai/http-proxy-middleware#1250: Both PRs modify decompression and content-encoding handling in response-interceptor.ts (main PR skips decompression for bodyless statuses, related PR extends decompression support to include zstd).

Poem

🐰 A HEAD without a body, a 204 so bare,
No gzip, no deflate—just empty air!
The interceptor now knows when to stop and rest,
Bodyless responses handled best! ✨

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name Status Explanation Resolution
Docstring Coverage ⚠️ Warning Docstring coverage is 50.00% which is insufficient. The required threshold is 80.00%. Write docstrings for the functions missing them to satisfy the coverage threshold.
✅ Passed checks (4 passed)
Check name Status Explanation
Title check ✅ Passed The PR title clearly and specifically summarizes the main change: fixing responseInterceptor to handle bodyless responses with content-encoding headers.
Linked Issues check ✅ Passed The PR addresses all coding requirements from issue #658: handling bodyless responses (HEAD/1xx/204/304) with content-encoding, avoiding decompression errors, preserving original status codes, and preventing error responses.
Out of Scope Changes check ✅ Passed All changes are directly related to fixing responseInterceptor for bodyless responses: implementation, tests (unit and e2e), changelog, and spell-check additions are all in-scope.
Description Check ✅ Passed Check skipped - CodeRabbit’s high-level summary is enabled.

✏️ Tip: You can configure your own custom pre-merge checks in the settings.

✨ Finishing Touches
📝 Generate docstrings
  • Create stacked PR
  • Commit on current branch
🧪 Generate unit tests (beta)
  • Create PR with unit tests
  • Commit unit tests in branch fix-responseInterceptor-bodyless-decompression-error

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@chimurai chimurai added bug and removed bug labels May 25, 2026
@chimurai chimurai added this to the v4.1 milestone May 25, 2026
@pkg-pr-new

pkg-pr-new Bot commented May 25, 2026

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npm i https://pkg.pr.new/http-proxy-middleware@1251

commit: 35b90cf

@coveralls

coveralls commented May 25, 2026

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Coverage Status

coverage: 94.815% (+0.07%) from 94.75% — fix-responseInterceptor-bodyless-decompression-error into master

@chimurai chimurai merged commit c65741c into master May 25, 2026
26 checks passed
@chimurai chimurai deleted the fix-responseInterceptor-bodyless-decompression-error branch May 25, 2026 12:01
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v4.1

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Successfully merging this pull request may close these issues.

[bug] Error fetching proxied request: unexpected end of file Webworker proxy with If-Modified-Since header

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