Including templates with blocks containing parameters lacking default values panics

[mvrhov]

The engine crashes with the following error:
"panic: runtime error: invalid memory address or nil pointer dereference"

Reporducer:

Main template

{{block body()}}
{{include "include.jet"}}
{{end}}

include.jet

{{block inputField(label)}}
{{label}}
{{end}}

the problem seems to be that the label doesn't have default value... If {{block inputField(label)}} is changed to {{block inputField(label="foo")}} then there is no crash

[annismckenzie]

While I agree that this looks like a bug I'd also like to point out that files with block definitions shouldn't' be included but rather imported. Is that possible for you? Even if you give the block parameter a default value it'll still be evaluated and executed which is probably not what you want? 🤔

[mvrhov]

I can do an import (thanks for the hint)that's no problem, but the panic remains and it would be nice if it would be fixed and an error reported instead.

[annismckenzie]

I agree with you – what would you say should the error message be? I'm asking because this is actually a layer 8 problem in that while you certainly can include a template with blocks they will be evaluated straight away which is almost never what you want – I've had a Jet-powered app with tons of templates in production for years now and I've never come across a use case where this is preferred to importing a template and yielding blocks at the appropriate points. Otherwise one might just as well drop the blocks( )and include the template as is.

We could actually think about failing the parsing of templates when including one that contains blocks but that would entail bumping the major to v3 which I really would like to avoid. But if we go ahead and just disallow including templates with blocks that contain parameters without default values then that's almost the same thing while being vastly more complicated to determine by the parser (I haven't actually looked at that part of the code base yet 😅). Thoughts? /cc @jhsx

[mvrhov]

I agree with you – what would you say should the error message be

"label not defined in this context". The same error or something very similar is already reported on different occasions.

I have a constant struggle with the jet. I'm really really used to the twig php template engine and I find a lot of things that were standard/normal there to be lacking here as e.g. they don't work, or the behavior is different than one would expect.
The next problem I'm probably going to face is how to extract the text to be translated from templates so it can be give to the translators.