fix(config): surface an invalid simulate config as a config error

[JulianMaurin]

A schema-invalid config uploaded by config simulate came back as
the simulator's HTTP 422 and was reported as a Mergify API failure
(exit 6) — even though the same fixture fails config validate
client-side with exit 8. The drift meant a local-config problem
looked like a service problem to scripts.

Add HttpClient::post_classifying, which lets a caller remap a
terminal status before the default flavor mapping, and use it in
simulate to map the simulator's 422 to a configuration error
(exit 8).

Co-Authored-By: Claude Opus 4.8 (1M context) noreply@anthropic.com

Depends-On: #1678

[JulianMaurin]

This pull request is part of a Mergify stack:

#	Pull Request	Link
1	fix(queue): treat a not-queued PR as a normal state, not an API error	#1678
2	fix(config): surface an invalid simulate config as a config error	#1679	👈
3	fix(ci): return a runtime error when scopes --write fails	#1680
4	fix(stack): exit not-found when checkout finds no stack	#1681
5	feat(cli): support the git-style help subcommand	#1682
6	docs(cli): correct stack reorder and scopes-send help text	#1683

[mergify]

Merge Protections

🟢 All 7 merge protections satisfied — ready to merge.

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🟢 ⛓️ Depends-On Requirements

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• depends-on = Mergifyio/mergify-cli#1678 [⛓️ fix(queue): treat a not-queued PR as a normal state, not an API error #1678]

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  • author = dependabot[bot]
  • author = mergify-ci-bot
  • author = renovate[bot]

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• title ~= ^(fix|feat|docs|style|refactor|perf|test|build|ci|chore|revert|ui)(?:\(.+\))?:

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🟢 📕 PR description

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[JulianMaurin]

Revision history

#	Type	Changes	Reason	Date
1	initial	987a30e		2026-06-25 07:49 UTC
2	rebase	987a30e → f18b064 (rebase only)		2026-06-25 07:49 UTC
3	rebase	f18b064 → 23baf94 (rebase only)		2026-06-25 07:56 UTC
4	rebase	23baf94 → 75d611c (rebase only)		2026-06-25 08:51 UTC

[Copilot]

Pull request overview

This PR adjusts HTTP error classification so config simulate reports a schema-invalid local config as a configuration error (exit 8) instead of a Mergify API failure (exit 6), and also updates queue show to treat “PR not in merge queue” (404) as a normal state with stdout output and exit 0.

Changes:

• Add HttpClient::post_classifying to allow callers to remap specific terminal HTTP statuses before ApiFlavor error mapping.
• Use post_classifying in config simulate to map simulator HTTP 422 to CliError::Configuration (exit 8), with regression tests.
• Change queue show 404 behavior to emit a not-queued message/document on stdout and return success, updating unit + live smoke tests accordingly.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
crates/mergify-queue/src/show.rs	Treat 404 “not queued” as a normal result; emit stdout output in human/JSON modes; update tests.
crates/mergify-core/src/http.rs	Introduce post_classifying and a classifier hook into the retry/execution path; add unit tests.
crates/mergify-config/src/simulate.rs	Map simulator 422 responses to configuration errors using the new HTTP helper; add regression test.
crates/mergify-cli/tests/live_smoke.rs	Update pinned contract for queue show not-queued case (stdout + exit 0).

---

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[mergify]

Queued — the merge queue status continues in this comment ↓.

[mergify]

Merge Queue Status

• ✅ Entered queue — 2026-06-25 12:37 UTC · Rule: default · triggered by merge protections
• ✅ Checks passed · on draft merge queue: checking main (71dd92c) and #1679 together #1690
• ✅ Merged — 2026-06-25 12:45 UTC · at 75d611c3dc1ef914c0eb96cd3d2b2f4bcaaecad1 · squash

This pull request spent 8 minutes 14 seconds in the queue, including 7 minutes 44 seconds running CI.

Required conditions to merge

• depends-on = Mergifyio/mergify-cli#1678 [⛓️ fix(queue): treat a not-queued PR as a normal state, not an API error #1678]
  • fix(config): surface an invalid simulate config as a config error #1679
• all of [🛡 Merge Protections rule Enforce conventional commit]:
  • title ~= ^(fix|feat|docs|style|refactor|perf|test|build|ci|chore|revert|ui)(?:\(.+\))?:
    • fix(config): surface an invalid simulate config as a config error #1679
• all of [🛡 Merge Protections rule 👀 Review Requirements]:
  • any of:
    • #approved-reviews-by>=2
      • fix(config): surface an invalid simulate config as a config error #1679
    • author = dependabot[bot]
      • fix(config): surface an invalid simulate config as a config error #1679
    • author = mergify-ci-bot
      • fix(config): surface an invalid simulate config as a config error #1679
    • author = renovate[bot]
      • fix(config): surface an invalid simulate config as a config error #1679
• all of [🛡 Merge Protections rule 📕 PR description]:
  • body ~= (?ms:.{48,})
    • fix(config): surface an invalid simulate config as a config error #1679
• all of [🛡 Merge Protections rule 🔎 Reviews]:
  • #changes-requested-reviews-by = 0
    • fix(config): surface an invalid simulate config as a config error #1679
  • #review-requested = 0
    • fix(config): surface an invalid simulate config as a config error #1679
  • #review-threads-unresolved = 0
    • fix(config): surface an invalid simulate config as a config error #1679
• all of [🛡 Merge Protections rule 🤖 Continuous Integration]:
  • all of:
    • check-success=ci-gate