Treat frame.path as nilable in frame filtering

lib/irb/debug.rb

@@ -49,7 +49,7 @@ def setup(irb)
           def DEBUGGER__.capture_frames(*args)
             frames = capture_frames_without_irb(*args)
             frames.reject! do |frame|
-              frame.realpath&.start_with?(IRB_DIR) || frame.path.start_with?("<internal:")
+              frame.realpath&.start_with?(IRB_DIR) || frame.path&.start_with?("<internal:")
             end
             frames
           end
@@ -87,7 +87,7 @@ def configure_irb_for_debugger(irb)
       module SkipPathHelperForIRB
         def skip_internal_path?(path)
           # The latter can be removed once https://github.com/ruby/debug/issues/866 is resolved
-          super || path.match?(IRB_DIR) || path.match?('<internal:prelude>')
+          super || path&.match?(IRB_DIR) || path&.match?('<internal:prelude>')
         end
       end
 

test/irb/helper.rb

@@ -139,8 +139,13 @@ def teardown
       end
     end
 
-    def run_ruby_file(timeout: TIMEOUT_SEC, &block)
-      cmd = [EnvUtil.rubybin, "-I", LIB, @ruby_file.to_path]
+    def run_ruby_file(timeout: TIMEOUT_SEC, via_irb: false, &block)
+      if via_irb
+        irb_path = File.expand_path("../../exe/irb", __dir__)
+        cmd = [EnvUtil.rubybin, "-I", LIB, irb_path, @ruby_file.to_path]
+      else
+        cmd = [EnvUtil.rubybin, "-I", LIB, @ruby_file.to_path]
+      end
       tmp_dir = Dir.mktmpdir
 
       @commands = []

test/irb/test_debugger_integration.rb

@@ -123,6 +123,25 @@ def test_next
       assert_match(/=>   2\| puts "hello"/, output)
     end
 
+    def test_next_with_irb_script
+      # Regression test for https://github.com/ruby/irb/issues/1159
+      # Running `irb file.rb` creates C frames with nil path that must be handled
+      write_ruby <<~'ruby'
+        binding.irb
+        puts "hello"
+      ruby
+
+      output = run_ruby_file(via_irb: true) do
+        type "next"
+        type "continue"
+      end
+
+      assert_not_match(/NoMethodError/, output)
+      assert_not_match(/undefined method.*start_with\?.*nil/, output)
+
+      assert_match(/irb\(main\):001>/, output)
+    end
+
     def test_break
       write_ruby <<~'RUBY'
         binding.irb