Currently, when I navigate to https://firefox-code-coverage.herokuapp.com/#/ I see the following error in the devtools console: TypeError: r is undefined [learn more] coverage.js:201:6 There is no stack trace, and the file location link takes me to this line: webpack:///src/utils/coverage.js 201| if (summary.pending === 0) { There is no `r` variable in the entire file. As a comparison, Chrome's devtools console shows this error message instead: Uncaught (in promise) TypeError: Cannot read property 'pending' of undefined

So there are 3 issues there: - The message could be better (like chrome one), which is what Bug 1259822 is about - We reference `r`, which is probably the name of the webpack'd variable. It would be nice to be able to retrieve the original variable name - There is no stacktrace Jan, I can't reproduce the issue anymore. Is it me or was it fixed ? Would you have a link where I can reproduce ? thanks !

The error still reproduces for me in Nightly, but it takes a while (I counted 21 seconds, you have to wait first for initial data to load, then for some additional polling to complete). It would be nice to extract/reduce the problematic code, or to create a reproducing test case, but I'm not sure how to do either.

Thanks Jan, I do see the message as well when waiting for a bit. For future reference, here's what we get from the server: ```json { "from": "server1.conn3.child1/consoleActor2", "type": "pageError", "pageError": { "errorMessage": "TypeError: r is undefined", "errorMessageName": "JSMSG_UNEXPECTED_TYPE", "exceptionDocURL": "https://developer.mozilla.org/docs/Web/JavaScript/Reference/Errors/Unexpected_type?utm_source=mozilla&utm_medium=firefox-console-errors&utm_campaign=default", "sourceName": "https://firefox-code-coverage.herokuapp.com/index.28f1b6e814e3c9950f13.js", "lineText": "", "lineNumber": 58, "columnNumber": 49548, "category": "content javascript", "timeStamp": 1532094691242, "warning": false, "error": false, "exception": true, "strict": false, "info": false, "private": false, "stacktrace": null, "notes": null } } ``` and indeed there's no stacktraces sent. I'll dig deeper to see why.

The message we get from the the nsIConsoleService observer [1] does not have the stack property we use to build the error packet (see [2]) [1] https://searchfox.org/mozilla-central/rev/8384a6519437f5eefbe522196f9ddf5c8b1d3fb4/devtools/server/actors/webconsole/listeners.js#70,88 [2] https://searchfox.org/mozilla-central/rev/8384a6519437f5eefbe522196f9ddf5c8b1d3fb4/devtools/server/actors/webconsole.js#1626

I do reproduce the no stack issue for uncaught promise rejection: data:text/html,<meta charset=utf8><script> function a () {b()} function b() {c();} function c() { new Promise(function(resolve,reject){ let x = r.pending; })} a(); </script>