feat(grpc_datasource): introduce RPCTransport abstraction with gRPC implementation

[fengyuwusong]

@coderabbitai summary

Summary

Refactor the gRPC data source so the dial path goes through a small RPCTransport interface instead of a hard-coded grpc.ClientConnInterface dependency. This is a no-op for behaviour and a no-op for existing callers, but it lets follow-up work plug additional transports (Connect, gRPC-Web, in-memory mocks) into the same data source pipeline.

This is the first of two PRs that together replace #1480.

Related

• Replaces: feat(grpc_datasource): add ConnectRPC transport for gRPC datasource #1480 (split into this PR + a follow-up that adds the ConnectRPC implementation)
• Follow-up: a second PR will add a Connect-protocol implementation of RPCTransport, regenerate the grpctest fixture via buf to also emit Connect handlers, and exercise the data source end-to-end with both transports.
• Consumed by: feat(router): add ConnectRPC transport for gRPC subgraphs cosmo#2808 (the router-side feature that motivated this work)

What's changed

pkg/engine/datasource/grpc_datasource

• New transport.go: defines the RPCTransport interface and a GRPCTransport implementation that wraps grpc.ClientConnInterface. The interface takes the same (ctx, methodFullName, input, output) shape the data source already passes to grpc.ClientConnInterface.Invoke, so swapping it in is mechanical.
• grpc_datasource.go: DataSource now keeps an RPCTransport rather than a raw grpc.ClientConnInterface. NewDataSource accepts the abstraction; a thin convenience wrapper NewDataSourceGRPC preserves the existing call shape for callers that already have a grpc.ClientConnInterface.
• New transport_test.go: shared helpers (newTestCompiler, findMessageDesc) plus a smoke test for GRPCTransport.Invoke. Helpers live here so the follow-up Connect transport tests can reuse them without a circular dependency.
• grpc_datasource_test.go, grpc_datasource_federation_test.go, grpc_datasource_spy_test.go: every existing NewDataSource(conn, …) call site is migrated onto NewDataSourceGRPC(conn, …). Tests still take a grpc.ClientConnInterface directly.

pkg/engine/datasource/graphql_datasource

• graphql_datasource.go: the planner constructed the gRPC data source inline via grpcdatasource.NewDataSource(p.grpcClient, …). With the new signature this would no longer compile, so the call switches to grpcdatasource.NewDataSourceGRPC(p.grpcClient, …). No behavioural change, no change to public Factory APIs.

Backward compatibility

• All existing NewDataSource consumers should switch to NewDataSourceGRPC. The old function name is kept but takes the abstraction, not a grpc.ClientConnInterface.
• No behaviour change for the gRPC dial path: GRPCTransport.Invoke simply forwards to the underlying client connection.

Testing

• pkg/engine/datasource/grpc_datasource: existing test suite (455+ cases) passes; new TestGRPCTransport_Invoke covers the wrapper directly.
• pkg/engine/datasource/graphql_datasource: existing tests pass against the migrated call site.

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 — N/A: no public-facing API change worth surfacing in docs at this stage; user-facing docs land with the consuming cosmo PR.
• I have read the Contributors Guide.

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[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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Configuration used: Path: .coderabbit.yaml

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Plan: Pro

Run ID: ec65926d-15d3-41ef-8232-c4ac9bba870a

📥 Commits

Reviewing files that changed from the base of the PR and between 3b64f82 and d16cca0.

📒 Files selected for processing (5)

• v2/pkg/engine/datasource/graphql_datasource/graphql_datasource.go
• v2/pkg/engine/datasource/grpc_datasource/grpc_datasource.go
• v2/pkg/engine/datasource/grpc_datasource/grpc_datasource_federation_test.go
• v2/pkg/engine/datasource/grpc_datasource/grpc_datasource_spy_test.go
• v2/pkg/engine/datasource/grpc_datasource/grpc_datasource_test.go

💤 Files with no reviewable changes (1)

• v2/pkg/engine/datasource/grpc_datasource/grpc_datasource.go

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📝 Walkthrough

Walkthrough

This PR introduces an RPCTransport interface and grpcTransport adapter, refactors grpcdatasource.DataSource to store and use an RPCTransport (constructor accepts RPCTransport), updates Load to call transport.Invoke, adds transport tests, and updates GraphQL wiring and all gRPC datasource tests to wrap connections with NewGRPCTransport.

Changes

gRPC Datasource Transport Abstraction

Layer / File(s)	Summary
Transport Interface & Implementation v2/pkg/engine/datasource/grpc_datasource/transport.go	Introduces RPCTransport interface with Invoke(ctx, methodFullName, input, output) and a grpcTransport adapter with NewGRPCTransport that delegates to grpc.ClientConnInterface.Invoke.
Transport Tests v2/pkg/engine/datasource/grpc_datasource/transport_test.go	Adds newTestCompiler, findMessageDesc, and TestGRPCTransport_Invoke smoke test asserting NewGRPCTransport(mi).Invoke(...) succeeds with dynamic protobuf messages.
DataSource Struct & Load Refactor v2/pkg/engine/datasource/grpc_datasource/grpc_datasource.go	Replaces internal cc grpc.ClientConnInterface with transport RPCTransport; NewDataSource now accepts an RPCTransport; Load performs RPCs using d.transport.Invoke(...).
GraphQL Datasource Integration v2/pkg/engine/datasource/graphql_datasource/graphql_datasource.go	ConfigureFetch updated to call NewDataSource with NewGRPCTransport(p.grpcClient) when constructing a gRPC-backed datasource.
Federation Test Updates v2/pkg/engine/datasource/grpc_datasource/grpc_datasource_federation_test.go	Five federation/entity-loading tests updated to pass NewGRPCTransport(conn) into NewDataSource; test behavior unchanged.
Spy Test Updates v2/pkg/engine/datasource/grpc_datasource/grpc_datasource_spy_test.go	Four spy tests updated to wrap conn with NewGRPCTransport when creating DataSource; assertions about RPC calls unchanged.
Comprehensive Test & Benchmark Updates v2/pkg/engine/datasource/grpc_datasource/grpc_datasource_test.go	Many tests and benchmarks updated to construct DataSource with NewGRPCTransport(...) across diverse test scenarios; no other config changes at call sites.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Possibly related PRs

• refactor: improve entity validation and mapping #1472: Modifies grpc datasource construction, DataSource internals, and Load/merge behavior in related code patterns.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely summarizes the main change: introducing an RPCTransport abstraction for the gRPC datasource with a gRPC implementation.
Description check	✅ Passed	The description is comprehensive and directly related to the changeset, explaining the refactoring's purpose, structure, and impact across multiple files.
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

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[fengyuwusong]

Hi @Noroth, I've addressed your review feedback in the latest commit (d16cca0):

Could you please take another look? Thanks!