On Sat, Jun 10, 2017 at 10:57 AM, 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
In converting to Vue, I dropped the ExecJS dependency. Instead of calling out to "a" JavaScript runtime on the server, I'm specifically shelling out to nodejs. This enables me to capture stderr, which I send both to the server logs and insert into the HTML sent to the client. https://github.com/rubys/wunderbar/blob/master/lib/wunderbar/vue.rb#L31 Note: you may need to do a view-source to see this result on the client as Vue is likely to remove these DOM nodes quickly. >>> 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
