Merge pull request #835 from Shopify/vs/avoid_mutating_document_tree_on_show_syntax_tree

Avoid mutating document tree in show syntax tree

Author: vinistock

lib/ruby_lsp/requests/show_syntax_tree.rb

@@ -47,7 +47,7 @@ def ast_for_range
         start_char = scanner.find_char_position(range[:start])
         end_char = scanner.find_char_position(range[:end])
 
-        queue = T.cast(@document.tree, SyntaxTree::Program).statements.body
+        queue = T.cast(@document.tree, SyntaxTree::Program).statements.body.dup
         found_nodes = []
 
         until queue.empty?

test/requests/show_syntax_tree_test.rb

@@ -62,5 +62,14 @@ def test_returns_ast_for_a_selection
 
       (assign (var_field (ident "bar")) (int "456"))
     AST
+
+    response = RubyLsp::Executor.new(store, @message_queue).execute({
+      method: "rubyLsp/textDocument/showSyntaxTree",
+      params: {
+        textDocument: { uri: "file:///fake.rb" },
+        range: { start: { line: 1, character: 0 }, end: { line: 1, character: 9 } },
+      },
+    }).response
+    refute_empty(response[:ast])
   end
 end