YardMap#spec_for_require: Get gem with version from bundle

[alisnic]

This is another stab at problem described in #508. Which basically makes solargraph work better when being run outside bundle (without bundle exec)

Why run solargraph outside bundle anyway?

Legacy projects usually have gems with old gem dependencies. This means that we want to use the latest solargraph version, we can't, because one of its depedencies cannot be satisfied:

Bundler could not find compatible versions for gem "diff-lcs":
  In snapshot (Gemfile.lock):
    diff-lcs (= 1.3)

  In Gemfile:
    rspec-rails was resolved to 3.5.2, which depends on
      rspec-expectations (~> 3.5.0) was resolved to 3.5.0, which depends on
        diff-lcs (>= 1.2.0, < 2.0)

    solargraph (~> 0.44.2) was resolved to 0.44.2, which depends on
      diff-lcs (~> 1.4)

Running `bundle update` will rebuild your snapshot from scratch, using only
the gems in your Gemfile, which may resolve the conflict.

Usually upgrading deps in such projects is a huge undertaking, which often does not justify installing solargraph

What this fix does?

We already know the version of each gem from the bundle from YardMap#process_gemsets. So instead of fetching gem specification using Gem::Specification.find_by_name(name) (which, while in bundler will resolve to the only and correct version of the gem), we can fetch it using Gem::Specification.find_by_name(name, version), which resolve to correct gem version even when solargraph runs outside bundle

Impact

Before fix in a sample project with Rails annotations:

[10] pry(#<Repl>)> yard_map.yardocs.size
=> 39
[11] pry(#<Repl>)> api_map.pins.select {|p| p.path && p.path.include?("ActionController") }.map(&:path)
=> 6

After fix in a sample project

[3] pry(#<Repl>)> yard_map.yardocs.size
=> 42
[4] pry(#<Repl>)> api_map.pins.select {|p| p.path && p.path.include?("ActionController") }.map(&:path).size
=> 565

[castwide]

Thanks, partner! This looks correct to me. I'm not ready to merge it yet because of other pending changes, but I wanted to make sure you knew it was on my radar and will probably be included in the next release.

[alisnic]

awesome! thank you!