Support DocumentLink request

This request uses the gem source comments generated by Tapioca to
let users quickly jump to the actual source of the definition.

lib/ruby_lsp/requests.rb

@@ -5,6 +5,7 @@ module RubyLsp
   # Supported features
   #
   # - {RubyLsp::Requests::DocumentSymbol}
+  # - {RubyLsp::Requests::DocumentLink}
   # - {RubyLsp::Requests::FoldingRanges}
   # - {RubyLsp::Requests::SelectionRanges}
   # - {RubyLsp::Requests::SemanticHighlighting}
@@ -15,6 +16,7 @@ module RubyLsp
   module Requests
     autoload :BaseRequest, "ruby_lsp/requests/base_request"
     autoload :DocumentSymbol, "ruby_lsp/requests/document_symbol"
+    autoload :DocumentLink, "ruby_lsp/requests/document_link"
     autoload :FoldingRanges, "ruby_lsp/requests/folding_ranges"
     autoload :SelectionRanges, "ruby_lsp/requests/selection_ranges"
     autoload :SemanticHighlighting, "ruby_lsp/requests/semantic_highlighting"

lib/ruby_lsp/requests/document_link.rb

@@ -0,0 +1,40 @@
+# typed: strict
+# frozen_string_literal: true
+
+module RubyLsp
+  module Requests
+    class DocumentLink < BaseRequest
+      extend T::Sig
+
+      sig { params(document: Document).void }
+      def initialize(document)
+        super
+
+        @links = T.let([], T::Array[LanguageServer::Protocol::Interface::DocumentLink])
+      end
+
+      sig { override.returns(T.all(T::Array[LanguageServer::Protocol::Interface::DocumentLink], Object)) }
+      def run
+        visit(@document.tree)
+        @links
+      end
+
+      sig { params(node: SyntaxTree::Comment).void }
+      def visit_comment(node)
+        match = node.value.match(%r{source://(?<path>.*):(?<line>\d+)$})
+        return unless match
+
+        file_path = File.join(Bundler.bundle_path, "gems", match[:path])
+        return unless File.exist?(file_path)
+
+        target = "file://#{file_path}##{match[:line]}"
+
+        @links << LanguageServer::Protocol::Interface::DocumentLink.new(
+          range: range_from_syntax_tree_node(node),
+          target: target,
+          tooltip: "Jump to the source"
+        )
+      end
+    end
+  end
+end

lib/ruby_lsp/server.rb

@@ -19,6 +19,10 @@ module RubyLsp
         )
       end
 
+      document_link_provider = if enabled_features.include?("documentLink")
+        Interface::DocumentLinkOptions.new(resolve_provider: false)
+      end
+
       folding_ranges_provider = if enabled_features.include?("foldingRanges")
         Interface::FoldingRangeClientCapabilities.new(line_folding_only: true)
       end
@@ -45,6 +49,7 @@ module RubyLsp
           ),
           selection_range_provider: enabled_features.include?("selectionRanges"),
           document_symbol_provider: document_symbol_provider,
+          document_link_provider: document_link_provider,
           folding_range_provider: folding_ranges_provider,
           semantic_tokens_provider: semantic_tokens_provider,
           document_formatting_provider: enabled_features.include?("formatting"),
@@ -85,6 +90,12 @@ module RubyLsp
       end
     end
 
+    on("testDocument/documentLink") do |request|
+      store.cache_fetch(request.dig(:params, :textDocument, :uri), :document_link) do |document|
+        RubyLsp::Requests::DocumentLink.new(document).run
+      end
+    end
+
     on("textDocument/foldingRange") do |request|
       store.cache_fetch(request.dig(:params, :textDocument, :uri), :folding_ranges) do |document|
         Requests::FoldingRanges.new(document).run

test/expectations/document_link/gem_source_comment.exp

@@ -0,0 +1,9 @@
+{
+    "result": [
+        {
+            "range": {"start": {"line": 0, "character": 0}, "end": {"line": 0, "character": 50}},
+            "target": "file://BUNDLER_PATH/gems/syntax_tree-3.0.0/lib/syntax_tree.rb#39",
+            "tooltip": "Jump to the source"
+        }
+    ]
+}

test/fixtures/gem_source_comment.rb

@@ -0,0 +1,3 @@
+# source://syntax_tree-3.0.0/lib/syntax_tree.rb:39
+def foo
+end

test/requests/document_link_expectations_test.rb

@@ -0,0 +1,20 @@
+# typed: true
+# frozen_string_literal: true
+
+require "test_helper"
+require "expectations/expectations_test_runner"
+
+class DocumentLinkExpectationsTest < ExpectationsTestRunner
+  expectations_tests RubyLsp::Requests::DocumentLink, "document_link"
+
+  def assert_expectations(source, expected)
+    actual = run_expectations(source)
+    assert_equal(map_expectations(json_expectations(expected)), JSON.parse(actual.to_json))
+  end
+
+  def map_expectations(expectations)
+    expectations.each do |expectation|
+      expectation["target"] = expectation["target"].sub("BUNDLER_PATH", Bundler.bundle_path.to_s)
+    end
+  end
+end