Suggest the correct method name in Ruby::NoMethod.

[ksss]

This pull request introduces a new feature to provide method suggestions when a Ruby::NoMethod error occurs in the steep LSP.
It leverages the did_you_mean gem to suggest possible corrections based on a dictionary of method name list by RBS.

textDocument/codeAction

I implemented this feature using textDocument/codeAction.
Currently only for Ruby::NoMethod, but can be extended to support Ruby::UnknownConstant and RBS::UnknownTypeName, etc.

Implementation

I implemented Steep::Services::CodeActionProvider.
It is designed for textDocument/codeAction with reference to Steep::Services::CompletionProvider.

Example

sample.rb

o = Object.new
o.calss

# @type var a: {a: 1}
a = _ = nil
x = a.foo(1)

With an editor that can use LSP, such as VSCode, it is possible to propose a “Quick Fix” and actually fix the problem.

[ParadoxV5]

👏

[ParadoxV5]

It doesn’t look right to construct a new temporary spellchecker for each diagnostic instance and on every call.
(Correct me if I’m wrong: I’m not familiar with how Did You Mean works.)

[ksss]

The initialization cost of DidYouMean::SpellChecker is very low.
https://github.com/ruby/did_you_mean/blob/2375fc5f2a66542df62cde3f08c2263677df3511/lib/did_you_mean/spell_checker.rb#L6-L10

module DidYouMean
  class SpellChecker
    def initialize(dictionary:)
      @dictionary = dictionary
    end

dictionary is a valid candidate for a method name, and I believe it's natural for the suggested candidates to differ depending on the error.

[ksss]

I reimplemented to use textDocument/codeAction.
The previous version, which added hover text.