denokv serve: 500 An internal server error occurred when attempting to sum a non kvu64

[johnspurlock-skymethod]

To reproduce: run denokv serve locally, connect via Deno.openKv, then attempt a sum operation on an existing non kvu64 value.

Expected:
http 4xx response, this is a non-retryable client error

Actual:
An error is logged: [ERROR denokv] Failed to write to database: Failed to perform 'sum' mutation on a non-U64 value in the database and an http 500 is returned to the client with body An internal server error occurred. The spec encourages retrying 5xx, so it's probably important to return a 4xx here instead.

[johnspurlock-skymethod]

Upgrading to Deno 1.38.1 from 1.37.2, I see the built-in Deno.openKv('http://localhost:4512/') client will actually retry forever in this case - another reason to use 4xx here.

[lucacasonato]

Yes, this is a bug.

[johnspurlock-skymethod]

Thanks!