Need more clear errors instead of "format for LanguageID not supported"

[vanarok]

If there are errors in the formatter or linter, efm will generate a misleading error: "format for LanguageID not supported: any-lang".

[mattn]

What is better?

[NfNitLoop]

@mattn

For example, I'm learning how to configure efm-langserver, and I kept getting the error "lint for LanguageID not supported: typescript", even though I definitely configured linting for typescript!

It turned out to be this line, skipping the config, because I hadn't enabled lint-after-open, which isn't even documented in schema.md. I had to read the source code to figure out what was going on.

A better message might be: "Skipping lint rule because lint-after-open=false".

[mattn]

Ah, sorry. Thanks for let me known. Can you make pull-request to fix issue?