[ReactNative] Make JS stack traces in Xcode prettier

Libraries/JavaScriptAppEngine/Initialization/ExceptionsManager.js

@@ -0,0 +1,71 @@
+/**
+ * Copyright 2004-present Facebook. All Rights Reserved.
+ *
+ * @providesModule ExceptionsManager
+ */
+'use strict';
+
+var Platform = require('Platform');
+var RCTExceptionsManager = require('NativeModules').ExceptionsManager;
+
+var loadSourceMap = require('loadSourceMap');
+var parseErrorStack = require('parseErrorStack');
+
+var sourceMapPromise;
+
+function handleException(e) {
+  var stack = parseErrorStack(e);
+  console.error(
+    'Error: ' +
+    '\n stack: \n' + stackToString(stack) +
+    '\n URL: ' + e.sourceURL +
+    '\n line: ' + e.line +
+    '\n message: ' + e.message
+  );
+
+  if (RCTExceptionsManager) {
+    RCTExceptionsManager.reportUnhandledException(e.message, format(stack));
+    if (__DEV__) {
+      (sourceMapPromise = sourceMapPromise || loadSourceMap())
+        .then(map => {
+          var prettyStack = parseErrorStack(e, map);
+          RCTExceptionsManager.updateExceptionMessage(e.message, format(prettyStack));
+        })
+        .then(null, error => {
+          console.error('#CLOWNTOWN (error while displaying error): ' + error.message);
+        });
+    }
+  }
+}
+
+function stackToString(stack) {
+  var maxLength = Math.max.apply(null, stack.map(frame => frame.methodName.length));
+  return stack.map(frame => stackFrameToString(frame, maxLength)).join('\n');
+}
+
+function stackFrameToString(stackFrame, maxLength) {
+  var fileNameParts = stackFrame.file.split('/');
+  var fileName = fileNameParts[fileNameParts.length - 1];
+
+  if (fileName.length > 18) {
+    fileName = fileName.substr(0, 17) + '\u2026' /* ... */;
+  }
+
+  var spaces = fillSpaces(maxLength - stackFrame.methodName.length);
+  return '  ' + stackFrame.methodName + spaces + '  ' + fileName + ':' + stackFrame.lineNumber;
+}
+
+function fillSpaces(n) {
+  return new Array(n + 1).join(' ');
+}
+
+// HACK(frantic) Android currently expects stack trace to be a string #5920439
+function format(stack) {
+  if (Platform.OS === 'android') {
+    return stackToString(stack);
+  } else {
+    return stack;
+  }
+}
+
+module.exports = { handleException };