Firefox's developer tools are really becoming great. "Copy as CURL" for the network tab was something in chrome that I really missed. Box model view which was super handy is now editable. Console showing stack traces along errors was long due. New Canvas debugger, eyedropper are very handy.
Font viewer, responsive design tools, the 3d view (very handy in debugging silly box model issues) and highlight painted area mode (handy in optimizing visualizations) are all things I love that I haven't been able to find good analogues for in other browsers.
Yeah it's pretty good, but it still has issues. My game uses a manifest.cache and the console/networking tab does not give good feedback with it. In chrome, the console will tell me, "This file could not be found". In Firefox, it gives me no feedback that was a problem... things just don't work as expected.
Also, I'm pretty convinced the dev tools have some sort of memory leak in them. Every 3-5 days I have to restart Firefox or my game runs so slow it's unplayable. I don't think it has to do with my code because I've got no persistent store and refreshing the page doesn't fix it. Restarting the browser always does.
Sometimes the debugger gets confused and puts breakpoints on things I no longer have breakpoints on.
The profiler does not have a very useful view. I can't figure out how to delete reports I've made without closing the dev tools. More importantly, I can't find a convenient way to answer the question, "What are the slowest parts of this code?" I have to do a lot of manual labor expanding deeply nested trees.
As I said, it's pretty good. These are just things I'd like to see improved, not things that drive me crazy. I prefer the dev tools to firebug because firebug takes a relatively long time to start up.
Re: this update, I'm embarrassed to say I didn't know console.error even existed (I don't consider myself a JS expert). I've been using `throw new Error("message")`. Will that show stack traces now, too? I always have to put breakpoints on the line with the throw to figure out the call stack. This can add a lot of time to my debugging if I'm not sure how to reproduce the error.
That is not true. I am sure add-ons can access the same stuff that built-in tools can. Most of the stuff are exposed as JS objects and there are APIs for a lot of stuff. APIs for devtools may be a bit hard to find the documentation sometimes. I guess it is because it is still being developed.
For me Firebug seems ~2x as slow (eg, for a 1s operation in native tools, firebug takes 2s). Opening Firebug on my workstation causes a noticable pause in all activity on page for several seconds, while opening the native tools only takes about half a second. All of Firefox's dev tools are still a ways from being as fast and bug-free as the Webkit tools (both Chrome and Safari). I can't cite specific examples since I dropped Firebug in Firefox once the native tools reached a certain level of quality. I just suggest trying to use 'em and seeing if you like them more than Firebug. I did.
I have a little bit of a hard time believing this: Firefox Addons can use almost all the APIs in the browser that built-in code can, and I'm at least led to believe the new debugging APIs the built-in tools are using are no exception to that rule. https://developer.mozilla.org/en-US/docs/Tools/Debugger-API seems to agree on those points. Or do you mean the tools themselves aren't extensible?
It's been a few years since I've written any Firefox code or touched XPCOM, so I could be looking on this without up-to-date information: I'd be interested if the Firebug authors or others have written any thoughts on struggles they have with this.
Font viewer, responsive design tools, the 3d view (very handy in debugging silly box model issues) and highlight painted area mode (handy in optimizing visualizations) are all things I love that I haven't been able to find good analogues for in other browsers.