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Date: Fri, 22 May 2020 17:56:16 +0100
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Subject: Re: [PHP-DEV] [RFC][DISCUSSION] Error Exceptions mode
From: rowan.collins@gmail.com (Rowan Tommins)

On 22/05/2020 17:08, Katie Volz wrote:
> I want to start a discussion on an RFC to add a declare() statement to
> convert all errors triggered within a file to exceptions.


Hi Katie,


Personally, I'm not a fan of promoting messages to exceptions in this 
way, because APIs designed to throw exceptions generally look rather 
different from ones designed to warn and continue, so blindly converting 
seems like putting a square peg in a round hole. However, I know people 
do it already, so will give my thoughts on the principle.


My main concern is that it needs a tighter definition of "error", and 
possibly a configurable one.

The snippet from the manual which you include in your draft RFC 
references the current global error_reporting setting. This makes sense 
with a global error handler, but less so for a per-file declare - it 
means the caller can choose whether exceptions are thrown, somewhat 
defeating the point. Perhaps the declare directive could take an error 
level as its argument, e.g. declare(error_exceptions=E_ALL-E_NOTICE)?

Relatedly, you would need to define how this interacts with the @ (error 
suppression or "shut up") operator - would that force the code to run 
past a point that would otherwise throw an exception? Again, I think 
that choice should be taken away from the caller, otherwise the author 
needs to account for both modes, e.g.

declare(error_exceptions=E_WARNING);
try {
     $fh = fopen($blah, $mode);
     // if caller can suppress ErrorExceptions, we still need to check 
if $fh is false
     // ...
} catch ( ErrorException $e ) {
     // the caller shouldn't actually care what happens, because we can 
catch it here
}


Other than that, there's the usual awkwardness of declare - it has to be 
set in each file, and new directives are errors in old versions of PHP. 
That doesn't necessarily mean we shouldn't use it for now, though.


Regards,

-- 
Rowan Tommins (né Collins)
[IMSoP]