Why is the FireFox debugger not showing full source code?

Question

I am trying to debug a web page in FireFox v42.0 Windows 10, where that web page goes through a proxy server and has code injected into it inline via <script>...</script> (not including a separate .js file) by the proxy server. When I right-click View Page Source, I see the original page plus the code I expect to see injected (and which is actually running). I also see the injected content in the DOM view of the Inspector tab. And it is also visible in the Network Tab in the Response section. However, when I view the same page in the debugger, the injected code is not visible, as if the page were not running through the proxy server.

Furthermore, if I insert a debugger; statement in the injected code, I do hit the breakpoint, but in the FireFox debugger tab it tells me I'm on line 550 of a file with only 173 lines in it according to FireFox. So I can not step through the code.

When I do the same thing in Chrome, I see what I'm expecting, which is the injected code in my page, and I am able to debug this code without problem.

I have cleared my cache to no effect. I looked at the Network tab and everything looks as expected there.

How and why is FireFox not showing me the actual page in the debugger tab (matching what's in View Source or the DOM view), and not letting my step through the injected code?

Answer 1

The below worked for me

1. Copy url from address bar and close the tab.
2. Open the url in private mode, the debugger shows the source.
3. Close private window and open in default mode, the debugger shows the source now.

Answer 2

There are a few bugs in Firefox that can cause this that I've encountered myself:

• A local caching issue which can be solved by first closing the dev tools window, hard-reloading the page (Ctrl/Cmd + Shift + R), then opening the debugger again.
• Trying to debug a tab in a container, but the source is showing the page as it would be outside a container. See bug 1375036). This particular case should now be fixed.
• Similar to the previous point, the debugger source showing you a slighty/completely different document to the one that's actually currently rendered by the browser. This is due to the fact that the debugger does not have access to the original markup & inline script the browser used to render the current page! Apparently designed that way to be memory efficient, but seems to ignore the fact that a developer wants to use the memory for storing the source, because they want the actual source. See bugs such as 1060732, 1149835, and 1472581.

If this is happening to you try debugging in the default/no container, or just do it in Chrome 🙁. If you can't debug in another browser, at least try a fresh profile before you "refresh" (nuke) Firefox as others suggest. You can do this from the about:profiles page (address must be typed manually or bookmarked), or by opening Firefox with the -P flag and creating a new one. To use those flags, run firefox -P --no-remote from a *nix/Mac terminal or C:\Program Files\Firefox Developer Edition\firefox.exe -P --no-remote from the Windows Run dialogue; the --no-remote flag is not required but allows you to run the new profile alongside your main one, and disregard links clicked in other programs.