[Template Inheritance] Missing note regarding different AppKernel location

[linaori]

I was having an issue regarding overriding twig template when following the TwigBundle example for custom error pages. The documentation points out that I should place it in app/Resources/TwigBundle/views/Exception/error.html.twig. I've tried this and it didn't work.

A little more context; I'm porting a Symfony1 application to Symfony2. Currently in a state where we have replaced 100% of the actions and we wanted to implement a fully Symfony2 error page.

Our AppKernel is located in a different directory: apps/myapp/lib/ due to compatibility with Symfony1. This was also the reason why the examples didn't work. Once I moved it to apps/myapp/lib/Resources/TwigBundle/views/Exception/error.html.twig, everything was working fine.

Scanning the docs, I missed a part where it mentioned that app/ is used because that's where the AppKernel is as it uses kernel.root_dir. I wasn't able to find a proper location to put this and a discussion on IRC with @wouterj pointed out that there might actually be more that needs moving around to solve this "confusion".

[wouterj]

What I proposed on IRC:

hmm, what do you think about this: move the "overriding bundle templates" section to http://symfony.com/doc/current/cookbook/bundles/override.html
and then add nothing more than a short section in the book referencing the new section

[javiereguiluz]

I don't like the idea of adding this explanation to the regular docs. To me, using multiple kernels is still a very uncommon edge case.

I propose instead to add this information, as well as any other issue specific to multi-kernel apps, to the article that describes how to use multiple kernels in Symfony (this article doesn't exist yet: see #997)

[linaori]

@javiereguiluz it's not about multiple kernels in particular. I had my kernel in a different locations due to framework migrations and seemingly simple things can become quite a pain without this being documented.

[javiereguiluz]

@iltar I see. Anyway, having the kernel in a different location looks even more uncommon to me. Maybe we could add a cookbook about how to move the kernel to another location and all the troubles that you'll find, such as the location of the templates.

[javiereguiluz]

@iltar almost two years after my last comment I think you were right and I was wrong 😞 I'm trying to fix this in #7844.