Identify which node in Foo::Bar::Baz causes a NameError

In Ruby 3.2 or later, a nested constant access like `Foo::Bar::Baz` is compiled to one instruction by the optimization ruby/ruby#6187 We try to spot which sub-node caues a NameError in question based on the constant name. We will give up if the same constant name is accessed in a nested access (`Foo::Foo`). Fixes #31

Author: mame

lib/error_highlight/base.rb

@@ -98,9 +98,40 @@ def initialize(node, point_type: :name, name: nil)
  end
  end
 
+ OPT_GETCONSTANT_PATH = (RUBY_VERSION.split(".").map {|s| s.to_i } <=> [3, 2]) >= 0
+ private_constant :OPT_GETCONSTANT_PATH
+
  def spot
  return nil unless @node
 
+ if OPT_GETCONSTANT_PATH && @node.type == :COLON2
+ # In Ruby 3.2 or later, a nested constant access (like `Foo::Bar::Baz`)
+ # is compiled to one instruction (opt_getconstant_path).
+ # @node points to the node of the whole `Foo::Bar::Baz` even if `Foo`
+ # or `Foo::Bar` causes NameError.
+ # So we try to spot the sub-node that causes the NameError by using
+ # `NameError#name`.
+ subnodes = []
+ node = @node
+ while node.type == :COLON2
+ node2, const = node.children
+ subnodes << node if const == @name
+ node = node2
+ end
+ if node.type == :CONST || node.type == :COLON3
+ if node.children.first == @name
+ subnodes << node
+ end
+
+ # If we found only one sub-node whose name is equal to @name, use it
+ return nil if subnodes.size != 1
+ @node = subnodes.first
+ else
+ # Do nothing; opt_getconstant_path is used only when the const base is
+ # NODE_CONST (`Foo`) or NODE_COLON3 (`::Foo`)
+ end
+ end
+
  case @node.type
 
  when :CALL, :QCALL

test/test_error_highlight.rb

@@ -818,6 +818,54 @@ def test_COLON2_2
  end
  end
 
+ def test_COLON2_3
+ assert_error_message(NameError, <<~END) do
+uninitialized constant ErrorHighlightTest::NotDefined
+
+ ErrorHighlightTest::NotDefined::Foo
+ ^^^^^^^^^^^^
+ END
+
+ ErrorHighlightTest::NotDefined::Foo
+ end
+ end
+
+ def test_COLON2_4
+ assert_error_message(NameError, <<~END) do
+uninitialized constant ErrorHighlightTest::NotDefined
+
+ ::ErrorHighlightTest::NotDefined::Foo
+ ^^^^^^^^^^^^
+ END
+
+ ::ErrorHighlightTest::NotDefined::Foo
+ end
+ end
+
+ if ErrorHighlight.const_get(:Spotter).const_get(:OPT_GETCONSTANT_PATH)
+ def test_COLON2_5
+ # Unfortunately, we cannot identify which `NotDefined` caused the NameError
+ assert_error_message(NameError, <<~END) do
+uninitialized constant ErrorHighlightTest::NotDefined
+ END
+
+ ErrorHighlightTest::NotDefined::NotDefined
+ end
+ end
+ else
+ def test_COLON2_5
+ assert_error_message(NameError, <<~END) do
+uninitialized constant ErrorHighlightTest::NotDefined
+
+ ErrorHighlightTest::NotDefined::NotDefined
+ ^^^^^^^^^^^^
+ END
+
+ ErrorHighlightTest::NotDefined::NotDefined
+ end
+ end
+ end
+
  def test_COLON3
  assert_error_message(NameError, <<~END) do
 uninitialized constant NotDefined