Go: map HTTP 400 to validation (not api_error)

[jeremy]

Problem

SPEC.md §6 prescribes 400 → validation to match the other five SDKs, but Go's checkResponse had no case http.StatusBadRequest, so 400 Bad Request fell through to the default arm and was mislabeled api_error. The SPEC self-tagged this as a [CONFLICT]/[static] carve-out with no conformance coverage.

Fix

• Add case http.StatusBadRequest → CodeValidation (retryable: false) to go/pkg/basecamp/helpers.go. This is a code/message correction, not a retry-behavior change.
• Resolve the SPEC carve-outs: mark the error-code table row, the mapping-algorithm step, the non-retryable-errors note, and Appendix D as [conformance]-verified; drop the stale "Go currently maps 400 to api_error" note.
• Add a 400 → validation case to the shared conformance fixture conformance/tests/error-mapping.json and a 400 row to helpers_test.go.

Tests / Verify

• helpers_test.go 400 row proven to fail pre-fix (api_error != validation).
• The new fixture case is green across all five conformance runners (Go, Kotlin, TypeScript, Ruby, Python) and passes conformance-fixtures-check.

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Part of the retry-contract follow-up (#456 / #460 / #461 / #476). Independent of the other two PRs in the series (no shared files).

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Summary by cubic

Maps HTTP 400 to validation in the Go SDK to align with SPEC §6 and other SDKs. Adds conformance coverage and a unit test; 400 remains non-retryable.

• Bug Fixes
  • Go: map 400 → validation in go/pkg/basecamp/helpers.go (retryable: false).
  • Tests: add 400 case to conformance/tests/error-mapping.json and helpers_test.go.
  • Spec: mark 400 mapping and non-retryable note as [conformance]; clarify mapping algorithm fallbacks.

^{Written for commit 28a3be8. Summary will update on new commits.}

[github-actions]

⚠️ Potential breaking changes detected:

• Change in error mapping: HTTP 400 responses are now mapped to a new error code CodeValidation instead of the more general api_error. This constitutes a breaking change as it alters the contract for error handling.

Review carefully before merging. Consider a major version bump.

[jeremy]

Series — retry-contract follow-up (branch fresh off main, each independent):

• Go: replay *WithBody request bodies across retries #481 — Go *WithBody retry body replay
• Go: map HTTP 400 to validation (not api_error) #482 — Go HTTP 400 → validation
• Go + Python: honor per-operation retry.max as a ceiling; add parity guard #483 — Go + Python per-op retry.max ceiling + parity guard

#481 and #483 both touch go/templates/client.tmpl (disjoint regions, no textual conflict). Whichever merges second should be rebased and regenerated (make -C go generate); the merged tree passes the Go generated-drift gate.

[Copilot]

Pull request overview

Aligns the Go SDK’s HTTP error-code mapping with SPEC.md §6 and the other SDKs by correctly classifying HTTP 400 as validation (instead of falling through to api_error). This closes a documented spec/implementation mismatch and adds conformance + unit-test coverage for the 400 case.

Changes:

• Go: map http.StatusBadRequest (400) to CodeValidation in checkResponse.
• Conformance: add a 400 → validation case to conformance/tests/error-mapping.json.
• Spec + tests: update SPEC.md to remove the prior carve-out and add a Go unit test row for 400.

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Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 1 comment.

File	Description
SPEC.md	Updates §6 error-code table/mapping algorithm and non-retryable notes to reflect 400→validation as conformance-verified.
go/pkg/basecamp/helpers.go	Adds an explicit 400→CodeValidation branch in checkResponse.
go/pkg/basecamp/helpers_test.go	Adds a 400 row to the checkResponse status→code/retryability table test.
conformance/tests/error-mapping.json	Adds a conformance fixture asserting 400 maps to validation with retryable=false.

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[cubic-dev-ai]

No issues found across 4 files

_{Re-trigger cubic}

[jeremy]

Addressed the bot review:

• [Copilot] Scoped the "[conformance]-verified" statement to steps 1–10 (explicitly enumerated statuses) and marked the two catch-all fallback steps (11: general 5xx; 12: any other non-mapped status) as [static].

[Copilot]

Pull request overview

Copilot reviewed 4 out of 4 changed files in this pull request and generated no new comments.