Add `node_id_for_backtrace_location` function

We want to use error highlight with eval'd code, specifically ERB
templates. We're able to recover the generated code for eval'd templates
and can get a parse tree for the ERB generated code, but we don't have a
way to get the node id from the backtrace location. So we can't pass the
right node into error highlight.

This patch gives us an API to get the node id from the backtrace
location so we can find the node in the AST.

Error Highlight PR: https://github.com/ruby/error_highlight/pull/26

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

1 files changed, 13 insertions, 0 deletions

diff --git a/test/ruby/test_ast.rb b/test/ruby/test_ast.rb
index aaf626e801..0932e93d5a 100644
--- a/test/ruby/test_ast.rb
+++ b/test/ruby/test_ast.rb
@@ -186,6 +186,19 @@ class TestAst < Test::Unit::TestCase
     end
   end
 
+  def test_node_id_for_location
+    exception = begin
+                  raise
+                rescue => e
+                  e
+                end
+    loc = exception.backtrace_locations.first
+    node_id = RubyVM::AbstractSyntaxTree.node_id_for_backtrace_location(loc)
+    node = RubyVM::AbstractSyntaxTree.of(loc, keep_script_lines: true)
+
+    assert_equal node.node_id, node_id
+  end
+
   def test_of_proc_and_method
     proc = Proc.new { 1 + 2 }
     method = self.method(__method__)