Introduce YANG LSP support

[esmasth]

This addresses #4355

[jcs090218]

There is a compile error:

In toplevel form:
clients/lsp-yang.el:56:2: Error: assignment to free variable ‘lsp-json-schemas’
..........................Test lsp-byte-compilation-test backtrace:


Test lsp-byte-compilation-test condition:

    (ert-test-failed
     ((should
       (byte-compile-file library))
      :form
      (byte-compile-file "/home/runner/work/lsp-mode/lsp-mode/clients/lsp-yang.el")
      :value nil))

Can you update our CHANGELOG.org too? :)

[esmasth]

I'll fix both in the next patch, thanks.

[esmasth]

@jcs090218 request your rereview here

[jcs090218]

Hmm... where does this variable come from? 🤔 This looks a bit odd to me. Usually, we don't change the variable at the root level.

[esmasth]

This comes from lsp-json.el in this repo. Is it better to append to the list? How does one do that for repeat alist?

[jcs090218]

I guess my question is, why is the YANG lsp client required to modify JSON language server settings? 🤔 Most language server clients are isolated, so it's a bit odd to see something like this.

[esmasth]

The json schema association settings could be set in init.el or .emacs for user specified associations as per variable provided by lsp-json.el. json schema associations are not always possible to encode in the json itself due to variability in editor support and how strictly json schema is written.

The association, hence, is provided via json schema handling subsystem configuration, which is the lsp-json.el in lsp-mode based emacs world as I see. The validation et al under the hood happens via vscode json language server.

Now, it should be possible for "emacs extensions" which are json based config consumers, to provide schema and association (like it is possible via vscode extensions), as an addition to a list of known associations, else each user of lsp-yang.el for example will have to make the association themselves, or there would be a central database of association configuration, neither of which scale.

[esmasth]

I will remove this setting for this commit, since setq overrides any default settings. There should be a mechanism provided by lsp-json.el which allows for appending any default or further setq.

[esmasth]

Thanks @jcs090218. Could you please guide me on how to resolve the failing checks? I don't know where to start.

[jcs090218]

Thanks @jcs090218. Could you please guide me on how to resolve the failing checks? I don't know where to start.

Don't worry about the failing tests. It's irrelevant to this PR.

[esmasth]

Thanks a lot @jcs090218. I have resolved the review comments hopefully, and also fixed the settings.json match pattern as a separate commit. OK to merge? I don't have permissions.

[jcs090218]

Thank you for your contribution!