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Date: Sat, 16 May 2015 17:48:07 -0600
Message-ID: <CAFMT4NoSC0ewg7y2=wBvCzNiNN4_RKmysJuBKncNPJmnWfaEqA@mail.gmail.com>
To: Rowan Collins <rowan.collins@gmail.com>
Cc: internals <internals@lists.php.net>
Content-Type: text/plain; charset=UTF-8
Subject: Re: [PHP-DEV] [VOTE] Exceptions in the engine
From: levim@php.net (Levi Morrison)

On Sat, May 16, 2015 at 5:44 PM, Levi Morrison <levim@php.net> wrote:
> On Sat, May 16, 2015 at 2:17 PM, Rowan Collins <rowan.collins@gmail.com> wrote:
>> On 16/05/2015 20:15, Levi Morrison wrote:
>>>
>>> The difference is that as time goes on and I've written code for PHP 7
>>> I was hit by this issue. It's an even bigger issue than even I
>>> realized during voting. How many people who voted on that issue have
>>> played with the code from both scenarios? Few, I can't guarantee it
>>> but given the historical precedent it's almost certainly true.
>>
>>
>> Can you give an example of the issue you were hit with? A sample program /
>> scenario, where failure to catch an EngineException caused behaviour that
>> was in some way worse than that under PHP 5?
>
> Here's a simplified example that illustrates one issue:
>
> <?php
>
> set_error_handler(function(){
>     echo "Handled.";
> });
>
> function foo(callable $f) {}
>
> try {
>     foo("bar is not callable");
> } catch (Exception $e) {
>     echo "Caught.";
> }
>
> echo "Done.", PHP_EOL;
>
> ?>
>
> In PHP 5 this prints "Handled.Done". Under PHP 7 this fails with:
>
>> Fatal error: Argument 1 passed to foo() must be callable, string given
>
> Note that if the TypeException had been caught by catch (Exception $e)
> the program would have still been correct. This kind of setup exists
> in PHPUnit for example; even if the test has some bad syntax or
> failure the testing harness needs to continue. There are other valid
> uses as well.
>
> The only way to make this work in both PHP 5 and 7 is to modify the
> code, despite the program being 100% correct under PHP 5 and the
> documented semantics.

To re-iterate now that I've shared an example: code is broken whether
it's part of Exception or not. I would prefer to not break the code
for people who purposefully utilized the semantics of error handlers
and exceptions to write their valuable products. The people who didn't
actually intended to catch all Exceptions should be the ones who feel
the pain.

It's also the principle of least astonishment: why isn't TypeException
caught by `catch (Exception $e)`?