On Sat, Jun 10, 2017 at 6:15 PM, sebb <seb...@gmail.com> wrote: > On 10 June 2017 at 17:22, Sam Ruby <ru...@intertwingly.net> wrote: >> On Sat, Jun 10, 2017 at 12:05 PM, sebb <seb...@gmail.com> wrote: >>> On 10 June 2017 at 16:58, Sam Ruby <ru...@intertwingly.net> wrote: >>>> On Sat, Jun 10, 2017 at 11:48 AM, sebb <seb...@gmail.com> wrote: >>>>> On 10 June 2017 at 15:57, Sam Ruby <ru...@intertwingly.net> wrote: >>>>>> On Sat, Jun 10, 2017 at 10:27 AM, sebb <seb...@gmail.com> wrote: >>>>>>> On 10 June 2017 at 15:20, Sam Ruby <ru...@intertwingly.net> wrote: >>>>>>>> On Sat, Jun 10, 2017 at 9:43 AM, sebb <seb...@gmail.com> wrote: >>>>>>>>> Hard to trace entry in error.log: >>>>>>>>> >>>>>>>>> App 11526 stderr: _ERROR TypeError: Cannot read property 'proposal' >>>>>>>>> of null >>>>>>>>> >>>>>>>>> The above error was fixed by cf054fd >>>>>>>>> >>>>>>>>> However finding the location of the error is not trivial, as there is >>>>>>>>> no obvious context. >>>>>>>>> >>>>>>>>> Most other Ruby errors are reported with a stack trace and line >>>>>>>>> numbers - why is this error different? >>>>>>>>> Can it be fixed to produce a more detailed error message? >>>>>>>> >>>>>>>> It is different in that it actually is a JavaScript error. >>>>>>>> >>>>>>>> A number of whimsy applications use react.js in a number of pages >>>>>>>> (many roster pages, all board agenda pages). If you view source on >>>>>>>> those pages, you will see a static rendering, then the loading of >>>>>>>> javascript files, then the data the scripts need. >>>>>>>> >>>>>>>> The static rendering is done by running the JavaScript application on >>>>>>>> the server and inserting its output into the page. That application >>>>>>>> may fail, which is what happened here. >>>>>>> >>>>>>> Can't such errors be caught by the code that runs JavaScript? >>>>>> >>>>>> I suspect that that would either require a change to ExecJS or for >>>>>> Wunderbar to use an alternative to ExecJS. Here is the relevant >>>>>> Wunderbar code: >>>>>> >>>>>> https://github.com/rubys/wunderbar/blob/master/lib/wunderbar/react.rb#L125 >>>>> >>>>> There's a rescue clause here: >>>>> >>>>> https://github.com/rubys/wunderbar/blob/master/lib/wunderbar/react.rb#L133 >>>>> >>>>> Is that catching all possible errors, or are some not catchable here? >>>> >>>> It is catching the error, and printing out the one line you are >>>> seeing. What is missing is anything resembling a stack traceback - >>>> which I presumed was the context you were originally looking for (see >>>> subject line?). >>> >>> Yes. >>> >>> If Wunderbar has control over what is printed, then surely it can add >>> some more context? >>> Eg the name of the file it is processing? >> >> I'm still not following. >> >> In the case of the Roster tool, here's the input: >> >> https://github.com/apache/whimsy/blob/master/www/roster/views/ppmc.html.rb > > This is not obvious from the error log > >> So, the name of the file being processed is 'app.js'. Here it is: >> >> https://github.com/apache/whimsy/blob/master/www/roster/views/app.js.rb >> >> Here's the generated javascript, which is run on both the client and server: >> >> https://whimsy.apache.org/roster/app.js >> >> The error you saw occurred some place in that generated file. >> >> It is not clear to me how logging the name 'app.js' would help with >> debugging. >> >> Knowing the page that failed would be more useful, but that already is >> in the log. > > Is it? > > A sample log extract shows: > > App 11526 stderr: 71.168.148.85 - johndament [10/Jun/2017:12:35:34 > +0000] "GET / HTTP/1.1" 304 - 1.6687 > App 11526 stderr: 71.168.148.85 - johndament [10/Jun/2017:12:35:36 > +0000] "GET /ppmc/ HTTP/1.1" 200 - 0.1865 > App 11526 stderr: _ERROR TypeError: Cannot read property 'proposal' of null > App 11526 stderr: 71.168.148.85 - johndament [10/Jun/2017:12:35:40 > +0000] "GET /ppmc/ariatosca HTTP/1.1" 200 - 1.8059 > App 11526 stderr: 71.168.148.85 - johndament [10/Jun/2017:12:35:40 > +0000] "GET /app.js HTTP/1.1" 200 - 0.0036 > App 11526 stderr: 71.168.148.85 - johndament [10/Jun/2017:12:54:49 > +0000] "GET / HTTP/1.1" 304 - 1.3152 > App 11526 stderr: 71.168.148.85 - johndament [10/Jun/2017:12:54:53 > +0000] "GET /ppmc/ HTTP/1.1" 304 - 0.1825 > App 11526 stderr: _ERROR TypeError: Cannot read property 'proposal' of null > App 11526 stderr: 71.168.148.85 - johndament [10/Jun/2017:12:54:55 > +0000] "GET /ppmc/ariatosca HTTP/1.1" 304 - 1.0298 > App 11526 stderr: 71.168.148.85 - johndament [10/Jun/2017:12:54:56 > +0000] "GET /app.js HTTP/1.1" 304 - 0.0004 > App 11526 stderr: _ERROR TypeError: Cannot read property 'proposal' of null > App 11526 stderr: 98.122.169.124 - rubys [10/Jun/2017:13:02:40 +0000] > "GET /ppmc/atlas HTTP/1.1" 200 - 0.5462 > App 11526 stderr: 98.122.169.124 - rubys [10/Jun/2017:13:02:41 +0000] > "GET /stylesheets/app.css HTTP/1.1" 200 - 0.0007 > App 11526 stderr: 98.122.169.124 - rubys [10/Jun/2017:13:02:41 +0000] > "GET /app.js HTTP/1.1" 200 - 0.0032 > > It's not at all obvious how to debug that, except that it is probably > associated with the /ppmc/ URL > > There's no indication that the error is a Javascript error. > Nor how to find the script that generated the Javascript > > When I tried forcing an error, the Javascript console shows: > > Uncaught TypeError: Cannot read property 'length' of undefined > at main.js.rb:144 > .... > > But the screen only shows 'TypeError: Cannot read property 'length' of > undefined' > > and the log likewise. > > I would expect the log (and possibly the screen) to show the first > part of the stack trace.
As I said, I know of no way to get any more information out of ExecJS. If you know of a way to get more information out, or know of a viable alternative to, ExecJS, please educate me. - Sam Ruby >>>> Or am I misunderstanding what you are looking for? >>>> >>>>>>>> Generally, the easiest way to debug such situations is to bring the >>>>>>>> page up in the browser and look at the error console. It used to be >>>>>>>> the case that in both Firefox and Chrome, you could click on the stack >>>>>>>> traceback in the console to see the original source; but for reasons I >>>>>>>> don't understand, with the current FIrefox you see the generated >>>>>>>> JavaScript instead. >>>>>>>> >>>>>>>> - Sam Ruby >>>>>> >>>>>> - Sam Ruby >>>> >>>> - Sam Ruby
