Summary

Fixes duplicate case compilation errors when multiple response patterns share the same schema.

Fixes #1

Problem

When an OpenAPI spec defines multiple response patterns (2XX, 3XX) using the same schema, ogen generated duplicate case statements in type switches, causing compilation failures:

./oas_response_encoders_gen.go:42:7: duplicate case *ResponseStatusCode in type switch
	./oas_response_encoders_gen.go:17:7: previous case

Solution

Added uniqueResponseTypes() function that deduplicates response types by Type.Name before generating switch cases.

This is safe because:

• Ogen's type caching ensures responses with the same Type.Name are identical
• Runtime status code differences are handled via the StatusCode field, not separate cases
• All responses with matching type names have identical encoding logic

Example

Before: Generated duplicate cases (compilation error)

switch response := response.(type) {
case *ResponseStatusCode:  // 2XX
    // ...
case *ResponseStatusCode:  // 3XX - duplicate!
    // ...
}

After: Single case handles both patterns

switch response := response.(type) {
case *ResponseStatusCode:
    code := response.StatusCode  // runtime value: 200, 201, 301, etc.
    w.WriteHeader(code)
    // ...
}

Changes

• Added uniqueResponseTypes() deduplication function in gen/templates.go
• Updated gen/_template/response_encode.tmpl to use deduplication
• Added integration test reproducing the exact issue scenario

Testing

• New integration test with 2XX/3XX patterns sharing schema
• Test verifies generated code compiles (bug prevented compilation)
• All existing tests pass
• Manually verified with reproduction case from issue