Add inlay hint support per LSP specification. Closes #103.

Author: xeger

lib/syntax_tree/language_server.rb

@@ -61,11 +61,19 @@ def run
            }
           write(id: id, result: [format(store[uri])])
         in {
+             # official RPC in LSP spec 3.17
+             method: "textDocument/inlayHint",
+             id:,
+             params: { textDocument: { uri: } }
+           }
+          write(id: id, result: inlay_hints(store[uri], false))
+        in {
+             # proprietary RPC (deprecated) between this gem and vscode-syntax-tree
              method: "textDocument/inlayHints",
              id:,
              params: { textDocument: { uri: } }
            }
-          write(id: id, result: inlay_hints(store[uri]))
+          write(id: id, result: inlay_hints(store[uri], true))
         in {
              method: "syntaxTree/visualizing",
              id:,
@@ -85,6 +93,9 @@ def run
     def capabilities
       {
         documentFormattingProvider: true,
+        inlayHintProvider: {
+          resolveProvider: false
+        },
         textDocumentSync: {
           change: 1,
           openClose: true
@@ -108,14 +119,18 @@ def format(source)
       }
     end
 
-    def inlay_hints(source)
+    def inlay_hints(source, proprietary)
       inlay_hints = InlayHints.find(SyntaxTree.parse(source))
       serialize = ->(position, text) { { position: position, text: text } }
 
-      {
-        before: inlay_hints.before.map(&serialize),
-        after: inlay_hints.after.map(&serialize)
-      }
+      if proprietary
+        {
+          before: inlay_hints.before.map(&serialize),
+          after: inlay_hints.after.map(&serialize)
+        }
+      else
+        inlay_hints.all
+      end
     rescue Parser::ParseError
       # If there is a parse error, then we're not going to return any inlay
       # hints for this source.

lib/syntax_tree/language_server/inlay_hints.rb

@@ -2,18 +2,19 @@
 
 module SyntaxTree
   class LanguageServer
-    # This class provides inlay hints for the language server. It is loosely
-    # designed around the LSP spec, but existed before the spec was finalized so
-    # is a little different for now.
+    # This class provides inlay hints for the language server. It existed
+    # before the spec was finalized so, so it provides two result formats:
+    # aligned with the spec (`#all`) and proprietary (`#before` and `#after`).
     #
     # For more information, see the spec here:
     # https://github.com/microsoft/language-server-protocol/issues/956.
     #
     class InlayHints < Visitor
-      attr_reader :stack, :before, :after
+      attr_reader :stack, :all, :before, :after
 
       def initialize
         @stack = []
+        @all = []
         @before = Hash.new { |hash, key| hash[key] = +"" }
         @after = Hash.new { |hash, key| hash[key] = +"" }
       end
@@ -98,6 +99,13 @@ def visit_if_op(node)
       def visit_rescue(node)
         if node.exception.nil?
           after[node.location.start_char + "rescue".length] << " StandardError"
+          all << {
+            position: {
+              line: node.location.start_line - 1,
+              character: node.location.start_column + "rescue".length
+            },
+            label: " StandardError"
+          }
         end
 
         super
@@ -129,6 +137,20 @@ def self.find(program)
       private
 
       def parentheses(location)
+        all << {
+          position: {
+            line: location.start_line - 1,
+            character: location.start_column
+          },
+          label: "₍"
+        }
+        all << {
+          position: {
+            line: location.end_line - 1,
+            character: location.end_column
+          },
+          label: "₎"
+        }
         before[location.start_char] << "₍"
         after[location.end_char] << "₎"
       end

test/language_server/inlay_hints_test.rb

@@ -11,40 +11,46 @@ def test_assignments_in_parameters
 
         assert_equal(1, hints.before.length)
         assert_equal(1, hints.after.length)
+        assert_equal(2, hints.all.length)
       end
 
       def test_operators_in_binaries
         hints = find("1 + 2 * 3")
 
         assert_equal(1, hints.before.length)
         assert_equal(1, hints.after.length)
+        assert_equal(2, hints.all.length)
       end
 
       def test_binaries_in_assignments
         hints = find("a = 1 + 2")
 
         assert_equal(1, hints.before.length)
         assert_equal(1, hints.after.length)
+        assert_equal(2, hints.all.length)
       end
 
       def test_nested_ternaries
         hints = find("a ? b : c ? d : e")
 
         assert_equal(1, hints.before.length)
         assert_equal(1, hints.after.length)
+        assert_equal(2, hints.all.length)
       end
 
       def test_bare_rescue
         hints = find("begin; rescue; end")
 
         assert_equal(1, hints.after.length)
+        assert_equal(1, hints.all.length)
       end
 
       def test_unary_in_binary
         hints = find("-a + b")
 
         assert_equal(1, hints.before.length)
         assert_equal(1, hints.after.length)
+        assert_equal(2, hints.all.length)
       end
 
       private