Use Clippy for Checking with Rust-analyzer, in Emacs with Eglot

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• related to Emacs

So according to Avery Larsen: Enable Clippy With rust-analyzer(Larsen 2023), setting "rust-analyzer.check.command": "clippy" in settings.json does the trick. I think this solution is related to VSCode's setting.

In our Emacs world, there is no such a file. However we have .dir-locals.el and Eglot neatly provides a project-specific configuration eglot-workspace-configuration, as showed in João Távora: Eglot Manual 5.1 Project-specific configuration(Távora 2022), for tweaking this settings.json-ish behavior.

Simply put the following in .dir-locals.el:

((nil
  . ((eglot-workspace-configuration
      . (:rust-analyzer (:check (:command "clippy")))))))

Side notes:

• clippy's feature is a super-set of cargo check, so don't worry about the caveat of missing features.
• in Emacs' JSON RPC GNU: 33.31 Parsing and generating JSON values(GNU 2018), false Boolean value is represented by :false, but somehow Eglot requires that to be :json-false, as its document shows. Nonetheless, you can use json-serialize to check the plist's serialization result (with :false replaced) to see if the output is as desired.