Improve Syntax and Runtime error backtraces

lib/execjs/external_runtime.rb

@@ -24,12 +24,12 @@ module ExecJS
 
       def exec(source, options = {})
         source = encode(source)
-        source = "#{@source}\n#{source}" if @source
+        source = "#{@source}\n#{source}" if @source != ""
         source = @runtime.compile_source(source)
 
         tmpfile = write_to_tempfile(source)
         begin
-          extract_result(@runtime.exec_runtime(tmpfile.path))
+          extract_result(@runtime.exec_runtime(tmpfile.path), tmpfile.path)
         ensure
           File.unlink(tmpfile)
         end
@@ -57,14 +57,25 @@ module ExecJS
           tmpfile
         end
 
-        def extract_result(output)
+        def extract_result(output, filename)
-          status, value = output.empty? ? [] : ::JSON.parse(output, create_additions: false)
+          status, value, stack = output.empty? ? [] : ::JSON.parse(output, create_additions: false)
           if status == "ok"
             value
-          elsif value =~ /SyntaxError:/
-            raise RuntimeError, value
           else
-            raise ProgramError, value
+            stack ||= ""
+            real_filename = File.realpath(filename)
+            stack = stack.split("\n").map do |line|
+              line.sub(" at ", "")
+                  .sub(real_filename, "(execjs)")
+                  .sub(filename, "(execjs)")
+                  .strip
+            end
+            stack.reject! { |line| ["eval code", "eval@[native code]"].include?(line) }
+            stack.shift unless stack[0].to_s.include?("(execjs)")
+            error_class = value =~ /SyntaxError:/ ? RuntimeError : ProgramError
+            error = error_class.new(value)
+            error.set_backtrace(stack + caller)
+            raise error
           end
         end
     end
@@ -158,7 +169,7 @@ module ExecJS
           if $?.success?
             output
           else
-            raise RuntimeError, output
+            raise exec_runtime_error(output)
           end
         end
 
@@ -181,7 +192,7 @@ module ExecJS
           if $?.success?
             output
           else
-            raise RuntimeError, output
+            raise exec_runtime_error(output)
           end
         end
       else
@@ -193,13 +204,20 @@ module ExecJS
           if $?.success?
             output
           else
-            raise RuntimeError, output
+            raise exec_runtime_error(output)
           end
         end
       end
       # Internally exposed for Context.
       public :exec_runtime
 
+      def exec_runtime_error(output)
+        error = RuntimeError.new(output)
+        lineno = output.split("\n")[0][/:(\d+)$/, 1] || 1
+        error.set_backtrace(["(execjs):#{lineno}"] + caller)
+        error
+      end
+
       def which(command)
         Array(command).find do |name|
           name, args = name.split(/\s+/, 2)

lib/execjs/ruby_racer_runtime.rb

@@ -12,11 +12,7 @@ module ExecJS
           begin
             @v8_context.eval(source)
           rescue ::V8::JSError => e
-            if e.value["name"] == "SyntaxError"
+            raise wrap_error(e)
-              raise RuntimeError, e.value.to_s
-            else
-              raise ProgramError, e.value.to_s
-            end
           end
         end
       end
@@ -37,11 +33,7 @@ module ExecJS
             begin
               unbox @v8_context.eval("(#{source})")
             rescue ::V8::JSError => e
-              if e.value["name"] == "SyntaxError"
+              raise wrap_error(e)
-                raise RuntimeError, e.value.to_s
-              else
-                raise ProgramError, e.value.to_s
-              end
             end
           end
         end
@@ -52,11 +44,7 @@ module ExecJS
           begin
             unbox @v8_context.eval(properties).call(*args)
           rescue ::V8::JSError => e
-            if e.value["name"] == "SyntaxError"
+            raise wrap_error(e)
-              raise RuntimeError, e.value.to_s
-            else
-              raise ProgramError, e.value.to_s
-            end
           end
         end
       end
@@ -96,6 +84,20 @@ module ExecJS
             result
           end
         end
+
+        def wrap_error(e)
+          error_class = e.value["name"] == "SyntaxError" ? RuntimeError : ProgramError
+
+          stack = e.value["stack"] || ""
+          stack = stack.split("\n")
+          stack.shift
+          stack = [e.message[/<eval>:\d+:\d+/, 0]].compact if stack.empty?
+          stack = stack.map { |line| line.sub(" at ", "").sub("<eval>", "(execjs)").strip }
+
+          error = error_class.new(e.value.to_s)
+          error.set_backtrace(stack + caller)
+          error
+        end
     end
 
     def name

lib/execjs/support/jsc_runner.js

@@ -9,10 +9,10 @@
       try {
         print(JSON.stringify(['ok', result]));
       } catch (err) {
-        print('["err"]');
+        print(JSON.stringify(['err', '' + err, err.stack]));
       }
     }
   } catch (err) {
-    print(JSON.stringify(['err', '' + err]));
+    print(JSON.stringify(['err', '' + err, err.stack]));
   }
 });

lib/execjs/support/jscript_runner.js

@@ -13,10 +13,10 @@
       try {
         print(JSON.stringify(['ok', result]));
       } catch (err) {
-        print('["err"]');
+        print(JSON.stringify(['err', err.name + ': ' + err.message, err.stack]));
       }
     }
   } catch (err) {
-    print(JSON.stringify(['err', err.name + ': ' + err.message]));
+    print(JSON.stringify(['err', err.name + ': ' + err.message, err.stack]));
   }
 });

lib/execjs/support/node_runner.js

@@ -11,10 +11,10 @@
       try {
         print(JSON.stringify(['ok', result]));
       } catch (err) {
-        print('["err"]');
+        print(JSON.stringify(['err', '' + err, err.stack]));
       }
     }
   } catch (err) {
-    print(JSON.stringify(['err', '' + err]));
+    print(JSON.stringify(['err', '' + err, err.stack]));
   }
 });

lib/execjs/support/spidermonkey_runner.js

@@ -9,10 +9,10 @@
       try {
         print(JSON.stringify(['ok', result]));
       } catch (err) {
-        print('["err"]');
+        print(JSON.stringify(['err', '' + err, err.stack]));
       }
     }
   } catch (err) {
-    print(JSON.stringify(['err', '' + err]));
+    print(JSON.stringify(['err', '' + err, err.stack]));
   }
 });

test/test_execjs.rb

@@ -253,38 +253,80 @@ class TestExecJS < Test
   end
 
   def test_exec_syntax_error
-    assert_raises ExecJS::RuntimeError do
+    begin
       ExecJS.exec(")")
+      flunk
+    rescue ExecJS::RuntimeError => e
+      assert e
+      assert e.backtrace[0].include?("(execjs):1"), e.backtrace.join("\n")
     end
   end
 
   def test_eval_syntax_error
-    assert_raises ExecJS::RuntimeError do
+    begin
       ExecJS.eval(")")
+      flunk
+    rescue ExecJS::RuntimeError => e
+      assert e
+      assert e.backtrace[0].include?("(execjs):1"), e.backtrace.join("\n")
     end
   end
 
   def test_compile_syntax_error
-    assert_raises ExecJS::RuntimeError do
+    begin
       ExecJS.compile(")")
+      flunk
+    rescue ExecJS::RuntimeError => e
+      assert e
+      assert e.backtrace[0].include?("(execjs):1"), e.backtrace.join("\n")
     end
   end
 
-  def test_exec_thrown_exception
+  def test_exec_thrown_error
+    begin
+      ExecJS.exec("throw new Error('hello')")
+      flunk
+    rescue ExecJS::ProgramError => e
+      assert e
+      assert e.backtrace[0].include?("(execjs):1"), e.backtrace.join("\n")
+    end
+  end
+
+  def test_eval_thrown_error
+    begin
+      ExecJS.eval("(function(){ throw new Error('hello') })()")
+      flunk
+    rescue ExecJS::ProgramError => e
+      assert e
+      assert e.backtrace[0].include?("(execjs):1"), e.backtrace.join("\n")
+    end
+  end
+
+  def test_compile_thrown_error
+    begin
+      ExecJS.compile("throw new Error('hello')")
+      flunk
+    rescue ExecJS::ProgramError => e
+      assert e
+      assert e.backtrace[0].include?("(execjs):1"), e.backtrace.join("\n")
+    end
+  end
+
+  def test_exec_thrown_string
     assert_raises ExecJS::ProgramError do
       ExecJS.exec("throw 'hello'")
     end
   end
 
-  def test_eval_thrown_exception
+  def test_eval_thrown_string
     assert_raises ExecJS::ProgramError do
-      ExecJS.exec("throw 'hello'")
+      ExecJS.eval("(function(){ throw 'hello' })()")
     end
   end
 
-  def test_compile_thrown_exception
+  def test_compile_thrown_string
     assert_raises ExecJS::ProgramError do
-      ExecJS.exec("throw 'hello'")
+      ExecJS.compile("throw 'hello'")
     end
   end