tcpserver.js does not propagate mjml compile errors for mjml >= 3

[liminspace]

tcpserver.js does not propagate mjml compile errors for mjml >= 3

[yourcelf]

mjml doesn't distinguish between error level ("errors" vs "warnings"), but with default options it is possible to have both errors and html output in the compiled result.

mjml2html does accept an options argument which could include {validationLevel: "strict"}, which causes it to throw an exception on the presence of any error - so that's another approach that could be taken to ensure that errors are thrown, rather than inspecting the errors array.

For my use case, I'd much prefer get an exception and not send an email if there's any possibility the email rendering was incomplete, even if it did render with warnings. In my setup now I'm running with my own version of tcpserver.js to get that behavior, so it isn't a burden to me if you think it better for django-mjml to have a more lax setup.

[liminspace]

Thanks @yourcelf,
mjml 4 hasn't released yet (it's just beta now), so I haven't check it yet.
I'll update django-mjml to support mjml 4 soon but just in separated branch, not master.

[yourcelf]

Apologies for my lack of clarity. This impacts mjml >= 3, not just v4+. I'm currently using 3.3.5, I expect anything in major version 3 will be affected (though I haven't checked earlier point releases).

[liminspace]

OK, I'll add mjml's errors checking.
But what about some warning messages in errors field? Is it possible if there is a rendered template and some errors together?

[liminspace]

@yourcelf, this issue is done in next release 0.5.0. Now you can check it in develop branch. Just set up mjml option level/validationLevel with strict value, see readme.