mimic node more closely

Author: LinusU

source-map-support.js

@@ -355,21 +355,35 @@ function getErrorSource(error) {
   return null;
 }
 
-// Mimic node's stack trace printing when an exception escapes the process
-function handleUncaughtExceptions(error) {
-  if (!error || !error.stack) {
-    console.error('Uncaught exception:', error);
-  } else {
-    var source = getErrorSource(error);
-    if (source !== null) {
-      console.error();
-      console.error(source);
-    }
-    console.error(error.stack);
+function printErrorAndExit (error) {
+  var source = getErrorSource(error);
+
+  if (source) {
+    console.error();
+    console.error(source);
   }
+
+  console.error(error.stack);
   process.exit(1);
 }
 
+function shimEmitUncaughtException () {
+  var origEmit = process.emit;
+
+  process.emit = function (type) {
+    if (type === 'uncaughtException') {
+      var hasStack = (arguments[1] && arguments[1].stack);
+      var hasListeners = (this.listeners(type).length > 0);
+
+      if (hasStack && !hasListeners) {
+        return printErrorAndExit(arguments[1]);
+      }
+    }
+
+    return origEmit.apply(this, arguments);
+  }
+}
+
 exports.wrapCallSite = wrapCallSite;
 exports.getErrorSource = getErrorSource;
 exports.mapSourcePosition = mapSourcePosition;
@@ -405,7 +419,7 @@ exports.install = function(options) {
     // generated JavaScript code will be shown above the stack trace instead of
     // the original source code.
     if (installHandler && !isInBrowser()) {
-      process.on('uncaughtException', handleUncaughtExceptions);
+      shimEmitUncaughtException();
     }
   }
 };

test.js

@@ -415,3 +415,25 @@ it('finds source maps with charset specified', function() {
   }
   fs.unlinkSync('.generated.js');
 });
+
+it('handleUncaughtExceptions is true with existing listener', function(done) {
+  var source = [
+    'process.on("uncaughtException", function() { /* Silent */ });',
+    'function foo() { throw new Error("this is the error"); }',
+    'require("./source-map-support").install();',
+    'process.nextTick(foo);',
+    '//@ sourceMappingURL=.generated.js.map'
+  ];
+
+  fs.writeFileSync('.original.js', 'this is the original code');
+  fs.writeFileSync('.generated.js.map', createSingleLineSourceMap());
+  fs.writeFileSync('.generated.js', source.join('\n'));
+
+  child_process.exec('node ./.generated', function(error, stdout, stderr) {
+    fs.unlinkSync('.generated.js');
+    fs.unlinkSync('.generated.js.map');
+    fs.unlinkSync('.original.js');
+    assert.equal((stdout + stderr).trim(), '');
+    done();
+  });
+});