Add Prism warnings in diagnostics

[snutij]

Motivation

Closes #1406

Add Prism warnings in diagnostics, actually we handle only errors.

Implementation

Same as error, but based on parse_result.warnings

Some minor changes in DiagnosticsExpectationsTest because we are not handling only Rubocop diagnostics now.

Automated Tests

Added fixtures and expectations.

Manual Tests

You can open test/fixtures/syntax_diagnostics.rb and see errors and warning.

[andyw8]

FYI @kddnewton

[andyw8]

I wonder if we should make this configurable (#1434) since if working on a legacy there project, there could be lot of noise.

Also, are we good with cases such as this where the Prism and RuboCop warnings covers the same thing, e.g.: (I see it was discussed in the issue).

[st0012]

I agree that this could be a configurable feature, which can be the first new config of .ruby-lsp.yml.

That said, I think it's fine to merge or even release this first to see how people react to it.

[kddnewton]

I don't think there will be much noise to be honest, there aren't that many kinds of warnings and all of them are trivially fixable.

I do think you could add a configuration option to limit it to "default"-level warnings versus "verbose"-level warnings though.

[vinistock]

Just a minor nitpick, but this is great 🚀.

Concerning configuring this, I honestly wouldn't worry about it ahead of time. If people start complaining about the warnings we can consider it, but I don't think it warrants increasing complexity.

However, I wonder if we can now shutdown some of the RuboCop rules in the rubocop-shopify configuration. Prism is surely going to be a lot faster in surfacing this and we can reduce the number of cops running.

@kddnewton do you have a list of which warnings are available? (Even better if you know which RuboCop rules they map to).

[kddnewton]

@vinistock they're listed here: https://github.com/ruby/prism/blob/f41ba6d7ecfc844535996e24525d4ea47c0a85db/src/diagnostic.c#L305-L314.

I haven't taken the time to line them up 1-to-1 with warnings from rubocop, but if you don't mind doing that it would actually help me. I need it for ruby/prism#2513.

[andyw8]

I'll take a stab at matching those to the RuboCop cops.

[andyw8]

[PM_WARN_AMBIGUOUS_FIRST_ARGUMENT_MINUS] -> Lint/AmbiguousOperator
[PM_WARN_AMBIGUOUS_FIRST_ARGUMENT_PLUS]  -> Lint/AmbiguousOperator
[PM_WARN_AMBIGUOUS_PREFIX_STAR]          -> Lint/AmbiguousOperator
[PM_WARN_AMBIGUOUS_SLASH]                -> Lint/AmbiguousRegexpLiteral
[PM_WARN_DUPLICATED_HASH_KEY]            -> Lint/DuplicateHashKey
[PM_WARN_DUPLICATED_WHEN_CLAUSE]         -> Lint/DuplicateCaseCondition
[PM_WARN_EQUAL_IN_CONDITIONAL]           -> Lint/AssignmentInCondition
[PM_WARN_END_IN_METHOD]                  -> Lint/Syntax
[PM_WARN_FLOAT_OUT_OF_RANGE]             -> Lint/FloatOutOfRange
[PM_WARN_INTEGER_IN_FLIP_FLOP]           -> Lint/FlipFlop

[vinistock]

Thanks for the contribution!