fix(clientgen): avoid shared JSON mapping collisions

[SebastienMelki]

Summary

• stop protoc-gen-go-client from emitting package-level JSON mapping files/methods owned by protoc-gen-go-http
• keep clientgen enum annotation validation and client runtime checks for go-http-provided custom unmarshaler methods
• add a combined go-http + go-client regression test for duplicate JSON mapping output
• update docs and consistency tests for the new ownership boundary

Fixes #246

Verification

• go test ./internal/clientgen ./internal/httpgen -count=1
• make lint
• ./scripts/run_tests.sh --fast

[github-actions]

🔍 CI Pipeline Status

✅ Lint: success
✅ Test: success
✅ Coverage: success
✅ Build: success
✅ Integration: success

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📊 Coverage Report: Available in checks above
🔗 Artifacts: Test results and coverage reports uploaded

[SebastienMelki]

Review

Clean ownership fix — go-http is now the sole emitter of package-level JSON mapping files, eliminating duplicate symbol errors when both Go plugins target the same package. The client dispatches through sebufUnmarshaler/json.Marshaler interfaces at runtime, so it picks up custom marshalers when present and falls back to protojson otherwise.

What I checked

• Deleted files (10 source + 15 golden) are genuinely duplicates of httpgen equivalents — no client-specific logic lost.
• enum_validation.go correctly preserves the fail-fast annotation conflict check without emitting code.
• generator.go:52-59 early return for service-less files is well-commented and correct.
• marshalRequest / unmarshalResponse dispatch logic unchanged — interface-based forwarding to go-http-owned methods works as before.
• Golden test expectations updated consistently — no references to deleted golden files remain.
• Consistency tests in httpgen properly removed the TestGoGeneratorsProduceIdentical* tests that compared go-http vs go-client output (now moot), while keeping TS + OpenAPI cross-generator checks intact.
• Combined generation test (TestCombinedGoHTTPAndGoClientGenerationDoesNotDuplicateJSONMappingFiles) is a solid regression guard.

Minor suggestions (non-blocking)

1. Combined test coverage: The test only exercises int64_deep_nested_encoding.proto. Adding a second fixture (e.g. flatten.proto or enum_encoding.proto) would catch regressions across more annotation families.

2. Client-only usage discoverability: If someone uses go-client without go-http, mapping annotations silently have no effect. The doc update in client-generation.md mentions this but it's easy to miss in a long sentence. A short callout box or generation-time warning could save users debugging time.

[codecov]

Codecov Report

❌ Patch coverage is 0% with 24 lines in your changes missing coverage. Please review.
✅ Project coverage is 34.56%. Comparing base (9e14c24) to head (b21866f).

Files with missing lines	Patch %	Lines
internal/clientgen/enum_validation.go	0.00%	21 Missing ⚠️
internal/httpgen/oneof_discriminator.go	0.00%	3 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main     #247      +/-   ##
==========================================
+ Coverage   28.88%   34.56%   +5.68%     
==========================================
  Files          75       67       -8     
  Lines       13157    10994    -2163     
==========================================
  Hits         3800     3800              
+ Misses       9160     6997    -2163     
  Partials      197      197              

Flag	Coverage Δ
unittests	34.56% <0.00%> (+5.68%)	⬆️

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[SebastienMelki]

Examples review follow-up pushed in be53144.

What changed:

• reviewed all example buf.gen.yaml files and regenerated every example with buf dep update && buf generate
• refreshed market-data-unwrap generated output/docs so go-http-owned unwrap marshalers are used alongside go-client
• clarified market-data-unwrap README: go-http owns custom unwrap marshalers; go-client consumes them when generated in the same package
• fixed restful-crud Makefile install to include protoc-gen-go-client
• fixed simple-api regeneration: clean now removes api/docs, and buf.gen.yaml enables mock generation because main.go uses NewMockUserServiceServer
• fixed a oneof discriminator generator bug surfaced by examples: emitted fmt.Errorf strings now use %w instead of %%w; added regression coverage and updated golden
• tidied example modules after regeneration

Verification:

• all examples: buf dep update && buf generate
• make lint
• ./scripts/run_tests.sh --fast
• go test ./... in every examples/* module with go.mod

[SebastienMelki]

LGTM. Clean ownership separation — all 9 JSON mapping generators removed from clientgen with no stale references, enum validation correctly retained, combined generation test verifies no duplicate files, and consistency tests properly updated. Docs reflect the new boundary.