fix(rpc): Fix http batch request to handle single item requests

[masonmcbride]

This pull request fixes the bug described in #3676. Using http, if a batch of requests only has one item, the request marshalls it as a single request and would create an error because the response logic is expecting a batch of responses. This pr changes how the client side unmarshalls the response by first trying to unmarshall it as a batch and returning it if successful. If it fails, it then tries to unmarshall as a response and returns that if successful. If both fail, it returns a Unmarshall error, as expected.

Omarsy's pr #3678 also fixed this issue from the server side inside the handlers.go file. I kept it as is but reverted earlier changes I made to it. The only file that changes in this pr is the client.go file.

I added a test that specifically verifies client side http batch request functionality, and this code is also covered by previous tests TestRPCClient_E2E_Endpoints from github.com/gnolang/gno/tm2/pkg/bft/rpc/client and TestClient_SendRequest from github.com/gnolang/gno/tm2/pkg/bft/rpc/lib/client/http

[Gno2D2]

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[notJoon]

duplicated with #3678

[n2p5]

It looks like we've resolved this issue with the RPC server patch #3678 , but I still think it is worthwhile thinking about how we could make the client more forgiving as well. I'll pass long feedback line in a review.

[n2p5]

Nice first pass, please see my comments in line for a few changes.

[n2p5]

@notJoon I still think this is worth patching so that Batching responses for the client will work, even on older test nets. This follows the robustness principle (Postel's Law). If we can coax a slightly malformed response into a correct one, then it is better for the end-user experience. But, with the server patch, all testnets moving forward should be fine with the server side-only change.

[masonmcbride]

I updated both the server side (Omar's solution) and the client side (mine) functions associated with batch requests so that they have the same functionality but are more readable. On the server side, it tries to unmarshall into a slice of Responses and if it can't it tried to unmarshall into a single Response but both cases perform the same process which is abstracted out as processRequest. On the client side, sendRequestCommon has R ResponseType which is a *types.RPCResponse | types.RPCResponses so it uses a switch case on the return type and exhausts the cases for a clear program flow.

[codecov]

Codecov Report

Attention: Patch coverage is 82.35294% with 3 lines in your changes missing coverage. Please review.

Files with missing lines	Patch %	Lines
tm2/pkg/bft/rpc/lib/client/http/client.go	82.35%	3 Missing ⚠️

📢 Thoughts on this report? Let us know!

[n2p5]

Let's keep this PR simple and let's remove the server handler changes, since it has been addressed in another PR and any refactoring we might want to do can come in a separate PR.

Also - since we are modifying the client.go, let's make sure that the functions your code touches have proper test coverage that address the expected behavior that this change is making.

Please add the tests and update your PR description as well.

[zivkovicmilos]

@masonmcbride

Thank you for opening up the PR 🙏

Gimme a bit of time to get to this and review, it look promising 🫡

[n2p5]

Thanks for taking the initiative on this. I'm going to wait for feedback from @zivkovicmilos or someone else from the core team to weigh in on this, but thanks for addressing my feedback and for adding test coverage.