[Go] Add strictResponseDecoding option to Go-server generator. Fixes issue #21446

[Chimdi511]

Summary

This PR introduces a new generator property, strictResponseDecoding, to the go-server generator. When enabled (the new default), every JSON decoder in generated handlers will call DisallowUnknownFields(), causing the server to reject any incoming payloads that contain fields not defined in the spec. Users can disable strict mode and allow extra fields by passing --additional-properties strictResponseDecoding=false. Fixes issue #21446.

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Changes

1. Codegen configuration

   • File: GoServerCodegen.java

   • What’s changed:

     • Added a STRICT_RESPONSE_DECODING CLI option (default: true).
     • Exposed strictResponseDecoding boolean in additionalProperties for use in templates.

2. Template guard

   • File: server.mustache

   • What’s changed:

     • Wrapped the call to decoder.DisallowUnknownFields() in a {{#strictResponseDecoding}}…{{/strictResponseDecoding}} block.

3. Documentation

   • File: Go-server README (modules/openapi-generator/README.md)

   • What’s changed:

     • Documented the new --additional-properties=strictResponseDecoding={true|false} flag, its default behavior, and usage example.

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Impact

• Backward compatibility:

  • Default behavior is now “strict” (reject unknown fields). Users relying on permissive parsing must explicitly opt out.

• Client generation:

  • No impact; this change applies only to the go-server generator.

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Usage Example

# Strict mode (default):
openapi-generator generate \
  -i api.yaml \
  -g go-server

# Permissive mode:
openapi-generator generate \
  -i api.yaml \
  -g go-server \
  --additional-properties strictResponseDecoding=false

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Checklist

• Added CLI option in GoServerCodegen.java
• Updated server.mustache template
• Updated Go-server README with documentation

@antihax @grokify @kemokemo @jirikuncar @ph4r5h4d @lwj5

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[wing328]

please merge the latest master to your branch and regenerate the samples again

let me know if you need any help

[wing328]

thanks for the pr

before introducing another option, did you try setting disallowAdditionalPropertiesIfNotPresent to false (or true which should be the default)?