fix: add extension code for po errors from websockets

[SkArchon]

Align websocket PO errors with normal http synchronous PO errors.

Summary by CodeRabbit

• Bug Fixes

  • Standardized websocket error responses for unknown persisted GraphQL operations (consistent message + extension code).
  • Consistent extension codes for batch-related rejections and request cancellation to improve client-facing error signals.

• Tests

  • Added tests covering persisted-operation safelist enforcement with enhanced logging for unknown subscription queries.

Checklist

• I have discussed my proposed changes in an issue and have received approval to proceed.
• I have followed the coding standards of the project.
• Tests or benchmarks have been added or updated.
• Documentation has been updated on https://github.com/wundergraph/docs-website.
• I have read the Contributors Guide.

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Organization UI

Review profile: CHILL

Plan: Pro

Run ID: 31eced47-9077-429f-9efa-6e412de5f2a2

📥 Commits

Reviewing files that changed from the base of the PR and between c673a3a and 5ae8311.

📒 Files selected for processing (4)

• router/core/batch.go
• router/core/errors.go
• router/core/graphql_prehandler.go
• router/core/websocket.go

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Walkthrough

Websocket error handling and GraphQL extension codes were standardized: persisted-operation "not found" errors now produce a structured PersistedQueryNotFound GraphQL error with an extension code. Tests were added/updated to assert the error payload and related logging. Batch and error-code constants were consolidated.

Changes

Cohort / File(s)	Summary
Websocket tests router-tests/subscriptions/websocket_test.go	Updated test expectation to assert structured PersistedQueryNotFound error payload; added test for persisted-operation safelist enforcement with LogUnknown enabled that also asserts a single "Unknown persisted operation found" log entry containing the original query text and sha256Hash.
Websocket error handling router/core/websocket.go	writeErrorMessage now recognizes PersistentOperationNotFoundError via errors.As and emits a single-element GraphQL error with message = "PersistedQueryNotFound" and extensions.code = ExtCodeErrPersistedQueryNotFound; other errors preserved. JSON payload marshaling simplified to always marshal that single error.
GraphQL error codes router/core/errors.go	Introduced shared ExtCodeErr* constants (including ExtCodeErrPersistedQueryNotFound, ExtCodeErrErrorRequestCanceled, ExtCodeErrBatchSizeExceeded, ExtCodeErrBatchSubscriptionsUnsupported) and updated writeOperationError to use these constants for specific cases.
Batch handling router/core/batch.go	Replaced inline/old batch extension code usage with ExtCodeErrBatchSizeExceeded; removed a local constants block for batch-related extension codes.
Operation prehandler router/core/graphql_prehandler.go	Batch-subscription rejection now sets httpGraphqlError.extensionCode to ExtCodeErrBatchSubscriptionsUnsupported (constant name alignment).

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• fix: request aborted shoudn't result in a fetch error #2741: Modifies router/core/errors.go error-handling and extension-code constants, closely related to the error-code refactor in this PR.

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 25.00% 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
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main purpose of the pull request: adding extension codes for persisted operation errors in websocket responses.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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✨ Finishing Touches

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Warning

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🔧 golangci-lint (2.11.4)

level=error msg="[linters_context] typechecking error: pattern ./...: directory prefix . does not contain main module or its selected dependencies"

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[github-actions]

Router image scan passed

✅ No security vulnerabilities found in image:

ghcr.io/wundergraph/cosmo/router:sha-5fdd9d1459a44bc79a89c55550e220c3a42f9d5a

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 65.64%. Comparing base (fdd035b) to head (98bed3f).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #2792       +/-   ##
===========================================
+ Coverage   46.28%   65.64%   +19.36%     
===========================================
  Files        1045      254      -791     
  Lines      139773    26457   -113316     
  Branches     8768        0     -8768     
===========================================
- Hits        64695    17368    -47327     
+ Misses      73326     7687    -65639     
+ Partials     1752     1402      -350     

Files with missing lines	Coverage Δ
router/core/batch.go	80.31% <100.00%> (ø)
router/core/errors.go	80.64% <100.00%> (ø)
router/core/graphql_prehandler.go	84.63% <100.00%> (ø)
router/core/websocket.go	76.51% <100.00%> (+0.57%)	⬆️

... and 806 files with indirect coverage changes

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