The JSONRPC spec says:
> If present, parameters for the rpc call MUST be provided as a
> Structured value
https://www.jsonrpc.org/specification#parameter_structures
(Where a "Structured value" is elsewhere defined as either a map or
array.)
This change skips the serialization of the `params` field for JSONRPC
method calls and notifications if the `params` field is the `None`
variant. This fixes compatibility with LSP servers which adhere closely
to that part of the spec: `ocamllsp` in the wild.
We should not depend on jsonrpc-core anymore:
* The project just announced it's no longer actively maintained[^1],
preferring their new implementation in `jsonrpsee`.
* The types are too strict: we would benefit from removing some
`#[serde(deny_unknown_fields)]` annotations to allow language
servers that disrespect the spec[^2].
* We don't use much of the project. Just the types out of core.
These are easy to embed directly into the `helix-lsp` crate.
[^1]: https://github.com/paritytech/jsonrpc/pull/674
[^2]: https://github.com/helix-editor/helix/issues/2786
