[CB-8468] Application freezes if breakpoint hits JavaScript callback invoked from native

• Type: Bug
• Status: Closed
• Priority: Minor
• Resolution: Fixed
• Fix Version/s: 4.0.0
• Component/s: cordova-ios, cordova-js
• Assignee: Shazron Abdullah
• Reporter: Marcus Pridham
• Created: 12/Feb/15 21:13
• Updated: 23/Aug/18 07:10
• Resolved: 29/May/15 00:30

Description

It you attach Safari to your application and hit a breakpoint in a Cordova callback the application freezes and you can't step through or continue. This only happens in breakpoints in the native to JavaScript callbacks. JavaScript breakpoints in other areas work fine.

A simple way to reproduce is to use the globalization plugin. Attach safari and put a breakpoint in the success callback.

navigator.globalization.getPreferredLanguage(function() {
        console.log("test"); // Will freeze if breakpoint set here
    }, function() {});

The problem seems to have to do with the webview stringByEvaluatingJavaScriptFromString. It is a synchronous call that can return the result of the JavaScript back to the native. The native code will crash if a breakpoint is hit while trying to execute the JavaScript. The workaround is to have your callback code in a setTimeout so it is not in the same context as the native stringByEvaluatingJavaScriptFromString call.

A workaround:

Open cordova.js and around line 281 replace:

callbackFromNative: function(callbackId, isSuccess, status, args, keepCallback) {
 

With:

    callbackFromNative: function(callbackId, isSuccess, status, args, keepCallback) {
       setTimeout(function() {
            cordova.callbackFromNative2(callbackId, isSuccess, status, args, keepCallback);
        }, 0);
    },
       
    callbackFromNative2: function(callbackId, isSuccess, status, args, keepCallback) {

Issue Links

• relates to: CB-4998 iOS Bridge sometimes stops working when debugger is attached.