Bug 1099071 - Display error message in console for thrown empty string;r=bgrins

MozReview-Commit-ID: IhOFhDnyMpF

devtools/client/webconsole/console-output.js

@@ -1349,7 +1349,7 @@ Messages.JavaScriptEvalOutput = function(evalResponse, errorMessage)
   // be useful to extensions customizing the console output.
   this.response = evalResponse;
 
-  if (errorMessage) {
+  if (typeof(errorMessage) !== "undefined") {
     severity = "error";
     msg = errorMessage;
     quoteStrings = false;

devtools/client/webconsole/jsterm.js

@@ -308,6 +308,11 @@ JSTerm.prototype = {
       return;
     }
     let errorMessage = response.exceptionMessage;
+    // Wrap thrown strings in Error objects, so `throw "foo"` outputs
+    // "Error: foo"
+    if (typeof(response.exception) === "string") {
+      errorMessage = new Error(errorMessage).toString();
+    }
     let result = response.result;
     let helperResult = response.helperResult;
     let helperHasRawOutput = !!(helperResult || {}).rawOutput;

devtools/client/webconsole/test/browser_webconsole_jsterm.js

@@ -142,4 +142,28 @@ function* testJSTerm(hud) {
   jsterm.clearOutput();
   yield jsterm.execute("undefined");
   yield checkResult("undefined", "undefined is printed");
+
+  // check that thrown strings produce error messages,
+  // and the message text matches that of a stringified error object
+  // bug 1099071
+  jsterm.clearOutput();
+  yield jsterm.execute("throw '';");
+  yield checkResult((node) => {
+    return node.parentNode.getAttribute("severity") === "error" &&
+      node.textContent === new Error("").toString();
+  }, "thrown empty string generates error message");
+
+  jsterm.clearOutput();
+  yield jsterm.execute("throw 'tomatoes';");
+  yield checkResult((node) => {
+    return node.parentNode.getAttribute("severity") === "error" &&
+      node.textContent === new Error("tomatoes").toString();
+  }, "thrown non-empty string generates error message");
+
+  jsterm.clearOutput();
+  yield jsterm.execute("throw { foo: 'bar' };");
+  yield checkResult((node) => {
+    return node.parentNode.getAttribute("severity") === "error" &&
+      node.textContent === Object.prototype.toString();
+  }, "thrown object generates error message");
 }

devtools/client/webconsole/webconsole.js

@@ -1,5 +1,5 @@
 /* -*- indent-tabs-mode: nil; js-indent-level: 2 -*- */
-/* vim: set ft= javascript ts=2 et sw=2 tw=80: */
+/* vim: set ft=javascript ts=2 et sw=2 tw=80: */
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */