3.0 Cell::__toString() must not throw an exception

[k-halaburda]

What i did:

in the console: /cake bake cell Sidebar
in my layout cell('Sidebar::nonexistentmethod');?>

What happened:

Warning (2): call_user_func_array() expects parameter 1 to be a valid callback, class 'App\View\Cell\SidebarCell' does not have a method 'categories' [ROOT\vendor\cakephp\cakephp\src\View\CellTrait.php, line 83]

and then:

Fatal Error
Error: Method App\View\Cell\SidebarCell::__toString() must not throw an exception

I think a fatal here is not intentional and dont really tell whats going on, warning should do the job. Php.net says You cannot throw an exception from within a __toString() method. Doing so will result in a fatal error.
http://www.php.net/manual/en/language.oop5.magic.php#object.tostring

Solution:

In View/Cell.php

public function __toString() {
try{
return $this->render();
catch(Exception $ex){
return '';
}
}

[markstory]

I don't think swallowing errors is a good idea. It might be better to return the exception message instead.

[ADmad]

..class 'App\View\Cell\SidebarCell' does not have a method 'categories'..
Such an error is in fact preferable. It's tell you exactly what's wrong and allows you to easily fix the problem.

[markstory]

Agreed, I think there are a few problems here:

• CellTrait::cell() does not check method names. We could skip the entire __toString() issue here if an exception was raised earlier. Adding method checks and raising exceptions will solve this.
• Cell::__toString() does not handle any errors in the view rendering well. Catching errors that occurred during rendering, and outputting the error string will solve this.

Does the above sound reasonable?

[k-halaburda]

I consider cells something similar to elements with its own logic (witch by the way are really great). I guess nonexistent cell methods should be threaten like non existend element files - people get used to that IMO

[josegonzalez]

I would prefer that we throw an exception instead of pretending the file doesn't exist. In fact, I'd say not throwing an exception for a non-existent element is a bug, given that this is certainly not what the user wanted.

[markstory]

Missing elements do trigger errors. I'll update element() to use an exception along with these changes.

[markstory]

Closing as #3676 is now open.