feat(backend): add Literal parameter validation in API Server and Driver. Fixes #12602

[khushiiagrawal]

Description of your changes:

This PR implements validation for Literal runtime parameters as part of KEP-11385.

Fixes #12602

Changes Made

1. Proto Definition (api/v2alpha1/pipeline_spec.proto)

• Added literals field to ComponentInputsSpec.ParameterSpec
• Regenerated Go protocol buffer bindings

2. API Server Validation (backend/src/apiserver/template/v2_template.go)

• Extended validatePipelineJobInputs() to check runtime parameters against the literals field
• If literals is non-empty, validates that the runtime value matches one of the allowed literals using proto.Equal()
• Returns clear error message when validation fails

3. Driver Validation (backend/src/v2/driver/resolve.go)

• Added validateLiteralParameter() helper function
• Integrated validation in resolveInputs() to check resolved upstream parameters against literal constraints

4. Unit Tests (backend/src/apiserver/template/v2_literal_test.go)

• Added 10 test cases covering:
  • Valid/invalid string, number, and boolean literal matches
  • Backward compatibility (empty/nil literals = no constraint)
  • Multiple parameters with literals

Backward Compatibility

• Parameters without literals field continue to work unchanged
• Empty literals array is treated the same as no literals (no constraint)

Test Results

All 16 tests pass (14 existing + 2 new test functions with sub-tests)

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[google-oss-prow]

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[github-actions]

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[google-oss-prow]

Hi @khushiiagrawal. Thanks for your PR.

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[Copilot]

Pull request overview

This PR implements validation for Literal runtime parameters to enforce that parameter values match a predefined set of allowed values, as specified in KEP-11385. The validation occurs at two critical points: when pipeline jobs are submitted to the API server and when the driver resolves upstream parameters at runtime.

Key Changes:

• Added literals field to the proto definition for parameter specifications
• Implemented validation logic in both API server and driver components
• Added comprehensive test coverage for API server validation

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 2 comments.

Show a summary per file

File	Description
api/v2alpha1/pipeline_spec.proto	Added literals field to ComponentInputsSpec.ParameterSpec to store allowed literal values
api/v2alpha1/go/pipelinespec/pipeline_spec.pb.go	Regenerated Go bindings with new literals field and getter method
api/v2alpha1/go/cachekey/cache_key.pb.go	Updated protoc version metadata (v6.33.2)
backend/src/apiserver/template/v2_template.go	Extended validatePipelineJobInputs() to validate runtime parameters against literal constraints using proto.Equal()
backend/src/v2/driver/resolve.go	Added validateLiteralParameter() helper and integrated validation in resolveInputs() to check resolved upstream parameters
backend/src/apiserver/template/v2_literal_test.go	Added comprehensive test suite with 10 test cases covering valid/invalid matches for strings, numbers, booleans, and backward compatibility scenarios

---

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[droctothorpe]

/ok-to-test

@alyssacgoins can you review this?

[khushiiagrawal]

hii @alyssacgoins , do let me know if any changes required :)

[alyssacgoins]

It looks like you updated this line for Description in additional to adding Literals. Can you revert this line back?

[khushiiagrawal]

This file is auto-generated by protoc from the .proto file. When I added the Literals field to pipeline_spec.proto and regenerated the Go code, the protoc compiler reformatted this line as part of the regeneration. I can't selectively revert just this line without breaking the generated code. The spacing change has no functional impact , it's just a formatting difference from the protobuf compiler version.
Thanks!

[alyssacgoins]

hii @alyssacgoins , do let me know if any changes required :)

Hey @khushiiagrawal thanks for your PR - I've added a round of comments.

[khushiiagrawal]

Hey @khushiiagrawal thanks for your PR - I've added a round of comments.

Thanks @alyssacgoins for taking the time to review and for the detailed comments. I’ll go through them and make the required changes.

[khushiiagrawal]

@droctothorpe @alyssacgoins
I’ve addressed all the review comments and pushed the updates.
The remaining failing checks appear to be due to test timeouts, not code changes.
Thanks!

[khushiiagrawal]

@alyssacgoins Please take a look!
Thanks.