Support nodes in spot

Fixes a bug where `spot` was using the wrong local variable.

We want to use error highlight with code that has been eval'd,
specifically ERB templates. We can recover the compiled source code of
the ERB template but we need an API to pass the node into error
highlight's `spot`.

Required Ruby PR: ruby/ruby#6593

Co-authored-by: Aaron Patterson <tenderlove@ruby-lang.org>

lib/error_highlight/base.rb

@@ -59,8 +59,7 @@ def self.spot(obj, **opts)
       Spotter.new(node, **opts).spot
 
     when RubyVM::AbstractSyntaxTree::Node
-      # Just for compatibility
-      Spotter.new(node, **opts).spot
+      Spotter.new(obj, **opts).spot
 
     else
       raise TypeError, "Exception is expected"

test/test_error_highlight.rb

@@ -1257,4 +1257,36 @@ def test_spot_with_backtrace_location
     assert_equal(22, spot[:last_column])
     assert_equal("      raise_name_error\n", spot[:snippet])
   end
+
+  def test_spot_with_node
+    omit unless RubyVM::AbstractSyntaxTree.respond_to?(:node_id_for_backtrace_location)
+
+    begin
+      raise_name_error
+    rescue NameError => exc
+    end
+
+    bl = exc.backtrace_locations.first
+    expected_spot = ErrorHighlight.spot(exc, backtrace_location: bl)
+    ast = RubyVM::AbstractSyntaxTree.parse_file(__FILE__, keep_script_lines: true)
+    node_id = RubyVM::AbstractSyntaxTree.node_id_for_backtrace_location(bl)
+    node = find_node_by_id(ast, node_id)
+    actual_spot = ErrorHighlight.spot(node)
+
+    assert_equal expected_spot, actual_spot
+  end
+
+  private
+
+  def find_node_by_id(node, node_id)
+    return node if node.node_id == node_id
+
+    node.children.each do |child|
+      next unless child.is_a?(RubyVM::AbstractSyntaxTree::Node)
+      found = find_node_by_id(child, node_id)
+      return found if found
+    end
+
+    return false
+  end
 end