fix(@typespec/http): `@head` response with body wrongly flags content type by Copilot · Pull Request #9869 · microsoft/typespec

Copilot · 2026-03-02T19:26:03Z

Add head-operation-no-body diagnostic to lib.ts
Revert payload.ts to use treatContentTypeAsHeader only
Update responses.ts to emit head-operation-no-body warning
Revert tsp-for-openapi3.ts and update openapi3 paths.test.ts
Update responses.test.ts and verbs.test.ts to use head-operation-no-body code
Fix formatting in verbs.test.ts
Use object (not array) in expectDiagnostics when expecting a single diagnostic

Original prompt

This section details on the original issue you should resolve

<issue_title>@head request with a body wrongly flags the content type</issue_title>
<issue_description>

Release 1.9.1 of @typespec/http updated so that the content-type header present in

I don't know if it is valid or not to do that with HEAD but the resulting openapi seems wrong as it now include the content type as header and the response has the wrong one

import "@typespec/http";

using Http;

@head
op listHead(): OkResponse | Error;

@error
model Error {
  @header
  contentType: "application/problem+json";

  type: string;
}

          headers:
            content-type:
              required: true
              schema:
                type: string
                enum:
                  - application/problem+json
          content:
            application/json:
              schema:
                $ref: '#/components/schemas/Error'
```</issue_description>

<agent_instructions>We should emit a warning when this happen but also fix it so that we still respect the content type depsite it being against the HTTP spec. This means we probably need to move the logic where we decide if content-type should be a type: contentType or a header in the http property</agent_instructions>

## Comments on the Issue (you are @copilot in this section)

<comments>
<comment_new><author>@timotheeguerin</author><body>
Http spec explicitly disallow this https://www.rfc-editor.org/rfc/rfc2616#page-54

So I believe we should add a diagnostic here. Now the question is do we want to police this or just it be a warning
1. Make it an error, doesn't matter what the regression was because it can't compile
2. Make it a warning, what do we do here:
  a. Drop the response body
  b. Act like any other verb and treat the content type as the one of the response</body></comment_new>
</comments>

Fixes @head request with a body wrongly flags the content type #9832

✨ Let Copilot coding agent set things up for you — coding agent works faster and does higher quality work when set up for your repo.

…erb-body warning Co-authored-by: timotheeguerin <1031227+timotheeguerin@users.noreply.github.com>

…est.ts, improve changeset Co-authored-by: timotheeguerin <1031227+timotheeguerin@users.noreply.github.com>

packages/openapi3/test/tsp-openapi3/utils/tsp-for-openapi3.ts

packages/http/src/lib.ts

packages/http/src/payload.ts

…treatContentTypeAsHeader, revert tsp-for-openapi3.ts Co-authored-by: timotheeguerin <1031227+timotheeguerin@users.noreply.github.com>

pkg-pr-new · 2026-03-04T19:31:08Z

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npm i https://pkg.pr.new/@typespec/http@9869

npm i https://pkg.pr.new/@typespec/openapi3@9869

commit: 0bf96a8

packages/http/src/lib.ts

packages/http/src/responses.ts

packages/http/test/responses.test.ts

packages/http/test/verbs.test.ts

timotheeguerin · 2026-03-05T13:08:38Z

@copilot rename the diagnostic to head-operation-no-body

Co-authored-by: timotheeguerin <1031227+timotheeguerin@users.noreply.github.com>

Copilot · 2026-03-05T13:18:44Z

@copilot rename the diagnostic to head-operation-no-body

Done in c6c60f9.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

telemetry.astro.build
- Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node node /home/REDACTED/work/typespec/typespec/website/node_modules/.bin/../astro/astro.js build pnpm pec/�� ebsite/src/conte--llmstxt uname /.bin/node --no-emit ture st/node-gyp-bin/generate-scenarios-summary sh /nod�� es && pnpm build:lib && vite bui--typekits node pec/node_modules/.bin/node ose l/reference sh node (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

Configure Actions setup steps to set up my environment, which run before the firewall is enabled
Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

timotheeguerin · 2026-03-05T13:39:33Z

@copilot fix formatting issue

Co-authored-by: timotheeguerin <1031227+timotheeguerin@users.noreply.github.com>

Copilot · 2026-03-05T13:49:31Z

@copilot fix formatting issue

Fixed in 433f22a — prettier wrapped the long expectDiagnostics line in verbs.test.ts.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

telemetry.astro.build
- Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node node /home/REDACTED/work/typespec/typespec/website/node_modules/.bin/../astro/astro.js build node s/.b�� tput-dir ../../website/src/content/docs/docs/libraries/events/reference node .0_tmp_3968/node_modules/pnpm/dist/node-gyp-bin/node . sh p-client/node_mogenerate-scenarios-summary sh sion�� tspd --enable-experimental gen-extern-signature . node /.bin/sh --no-emit sh rsioning/referendoc sh (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

Configure Actions setup steps to set up my environment, which run before the firewall is enabled
Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

packages/http/test/verbs.test.ts

….test.ts Co-authored-by: timotheeguerin <1031227+timotheeguerin@users.noreply.github.com>

Copilot · 2026-03-05T14:02:35Z

Just as a heads up, I was blocked by some firewall rules while working on your feedback. Expand below for details.

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

telemetry.astro.build
- Triggering command: /home/REDACTED/work/_temp/ghcca-node/node/bin/node node /home/REDACTED/work/typespec/typespec/website/node_modules/.bin/../astro/astro.js build node cal/�� ebsite/src/conte--llmstxt --local /.bin/node import @typespecnode git st/node-gyp-bin/generate-scenarios-summary node /nod�� build.json sh t/node_modules/.bin/tspd --no-emit l/reference st/node-gyp-bin/doc sh (dns block)

If you need me to access, download, or install something from one of these locations, you can either:

Configure Actions setup steps to set up my environment, which run before the firewall is enabled
Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

timotheeguerin · 2026-03-05T16:53:06Z

@copilot update the target for that new diagnostic to be the operation

Co-authored-by: timotheeguerin <1031227+timotheeguerin@users.noreply.github.com>

github-actions · 2026-03-05T19:33:49Z

All changed packages have been documented.

✅ @typespec/http

Show changes

`@typespec/http` - fix ✏️

Emit a head-no-body warning when a @head operation response contains a body (HTTP spec: "head request must not return a message-body in the response").,> - Fix the content-type-ignored warning incorrectly firing for @head responses that have a content-type header but no body.

Initial plan

0737d66

Copilot AI assigned Copilot and timotheeguerin Mar 2, 2026

Copilot started work on behalf of timotheeguerin March 2, 2026 19:26 View session

fix: @Head request with body wrongly flags content type - emit head-v…

d4a3b1f

…erb-body warning Co-authored-by: timotheeguerin <1031227+timotheeguerin@users.noreply.github.com>

microsoft-github-policy-service bot added lib:http emitter:openapi3 Issues for @typespec/openapi3 emitter labels Mar 2, 2026

fix: address code review - add head-verb-body warning test in verbs.t…

40877dc

…est.ts, improve changeset Co-authored-by: timotheeguerin <1031227+timotheeguerin@users.noreply.github.com>

Copilot AI changed the title ~~[WIP] Fix content type flagging for HEAD requests~~ fix(@typespec/http): @head response with body uses wrong content-type and missing warning Mar 2, 2026

Copilot finished work on behalf of timotheeguerin March 2, 2026 19:58

timotheeguerin reviewed Mar 3, 2026

View reviewed changes

packages/openapi3/test/tsp-openapi3/utils/tsp-for-openapi3.ts Show resolved Hide resolved

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Copilot started work on behalf of timotheeguerin March 3, 2026 00:21 View session

fix: address reviewer feedback - rename to head-no-body, simplify to …

a24fe2f

…treatContentTypeAsHeader, revert tsp-for-openapi3.ts Co-authored-by: timotheeguerin <1031227+timotheeguerin@users.noreply.github.com>

Copilot AI changed the title ~~fix(@typespec/http): @head response with body uses wrong content-type and missing warning~~ fix(@typespec/http): @head response with body wrongly flags content type Mar 3, 2026

Copilot finished work on behalf of timotheeguerin March 3, 2026 00:35

markcowl reviewed Mar 4, 2026

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Copilot started work on behalf of timotheeguerin March 5, 2026 13:08 View session

fix: rename diagnostic to head-operation-no-body

c6c60f9

Co-authored-by: timotheeguerin <1031227+timotheeguerin@users.noreply.github.com>

timotheeguerin added the int:azure-specs Run integration tests against azure-rest-api-specs label Mar 5, 2026

Copilot finished work on behalf of timotheeguerin March 5, 2026 13:20

Copilot started work on behalf of timotheeguerin March 5, 2026 13:39 View session

fix: format verbs.test.ts

433f22a

Co-authored-by: timotheeguerin <1031227+timotheeguerin@users.noreply.github.com>

Copilot finished work on behalf of timotheeguerin March 5, 2026 13:50

timotheeguerin reviewed Mar 5, 2026

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Copilot started work on behalf of timotheeguerin March 5, 2026 13:52 View session

fix: remove array wrapper from single expectDiagnostics call in verbs…

d430ee8

….test.ts Co-authored-by: timotheeguerin <1031227+timotheeguerin@users.noreply.github.com>

Copilot finished work on behalf of timotheeguerin March 5, 2026 14:02

Copilot started work on behalf of timotheeguerin March 5, 2026 16:53 View session

Changes before error encountered

03b9e2b

Co-authored-by: timotheeguerin <1031227+timotheeguerin@users.noreply.github.com>

Copilot stopped work on behalf of timotheeguerin due to an error March 5, 2026 17:27
Workflow completed but conclusion is not available. This may indicate rate limiting or API issues.

Merge branch 'main' into copilot/fix-head-request-content-type

5970422

Merge branch 'main' into copilot/fix-head-request-content-type

0b76b0f

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@typespec/http - fix ✏️

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`@typespec/http` - fix ✏️