+ Add Source::TreeRewriter.default_diagnostics

lib/parser/source/tree_rewriter.rb

@@ -95,6 +95,7 @@ def initialize(source_buffer,
                      crossing_deletions: :accept,
                      different_replacements: :accept,
                      swallowed_insertions: :accept)
+        @diagnostics = nil
         @source_buffer = source_buffer
         @in_transaction = false
 
@@ -321,12 +322,20 @@ def transaction
       # Provides access to a diagnostic engine.
       # By default outputs diagnostic to $stderr
       #
-      def diagnostics
-        @diagnostics ||= Diagnostic::Engine.new.tap do |engine|
+      def self.default_diagnostics
+        @default_diagnostics ||= Diagnostic::Engine.new.tap do |engine|
           engine.consumer = -> diag { $stderr.puts diag.render }
         end
       end
 
+      ##
+      # Provides access to a diagnostic engine.
+      # By default: self.class.default_diagnostics
+      #
+      def diagnostics
+        @diagnostics ||= self.class.default_diagnostics.dup
+      end
+
       def in_transaction?
         @in_transaction
       end
@@ -409,11 +418,12 @@ def policy(event)
       def trigger_policy(event, range: raise, conflict: nil, **arguments)
         action = policy(event)
         diag = Parser::Diagnostic.new(POLICY_TO_LEVEL[action], event, arguments, range)
-        @diagnostics.process(diag)
+        engine = @diagnostics || self.class.default_diagnostics
+        engine.process(diag)
         if conflict
           range, *highlights = conflict
           diag = Parser::Diagnostic.new(POLICY_TO_LEVEL[action], :"#{event}_conflict", arguments, range, highlights)
-          @diagnostics.process(diag)
+          engine.process(diag)
         end
         raise Parser::ClobberingError, "Parser::Source::TreeRewriter detected clobbering" if action == :raise
       end

test/test_source_tree_rewriter.rb

@@ -298,6 +298,19 @@ def test_ordered_replacements
                   result.map {|r, s| [r.to_range, s]}
                 )
   end
+
+  def test_default_diagnostics
+    default = Parser::Source::TreeRewriter.default_diagnostics
+    before = default.consumer
+    diagnostics = []
+    default.consumer = -> diag { diagnostics << diag.render }
+    rewriter = Parser::Source::TreeRewriter.new(@buf, swallowed_insertions: :warn)
+    rewriter.replace(@ll, 'xx')
+    rewriter.remove(@hello)
+    assert_equal(2, diagnostics.size)
+  ensure
+    default.consumer = before
+  end
 end
 
 class TestSourceTreeRewriterImport < Minitest::Test