Newsgroups: php.internals
Path: news.php.net
Xref: news.php.net php.internals:69602
Mailing-List: contact internals-help@lists.php.net; run by ezmlm
To: internals@lists.php.net,Julien Pauli <jpauli@php.net>
Message-ID: <525FC834.4060501@php.net>
Date: Thu, 17 Oct 2013 12:21:24 +0100
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130625 Thunderbird/17.0.7
MIME-Version: 1.0
References: <D7.A0.22512.AE09F525@pb1.pair.com> <CAMUwpuSG9GF8kC6BkULmcG+KYvdm6gubQN36B2D2NFi5235qmg@mail.gmail.com>
In-Reply-To: <CAMUwpuSG9GF8kC6BkULmcG+KYvdm6gubQN36B2D2NFi5235qmg@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Content-Transfer-Encoding: 7bit
Subject: Re: [PHP-DEV] Assertions
From: krakjoe@php.net (Joe Watkins)

On 10/17/2013 11:51 AM, Julien Pauli wrote:
> On Thu, Oct 17, 2013 at 9:25 AM, Joe Watkins <krakjoe@php.net> wrote:
>
>> Morning All,
>>
>>          I'd like to draw some attention to how poor assertions are in PHP.
>>
>>          The current assertion API is not usable in my opinion; it has a
>> considerable overhead, relies on eval(), and is generally poorly
>> implemented.
>>
>>          I have done some work toward implementing assert at the Zend
>> level, giving assertions a more modern, usable feel to them.
>>
>>          https://github.com/krakjoe/**php-src/compare/assert<https://github.com/krakjoe/php-src/compare/assert>
>>
>>          This implementation of assert removes the old implementation and
>> associated functions and INI settings, and replaces it with a single INI
>> setting to control assertion compilation.
>>
>>          Failed assertions throw an AssertionException (which extends
>> ErrorException with a severity of E_ERROR), setting the message of the
>> exception to the expression asserted.
>>
>>          The syntax of assertion is the same as [all] other languages:
>>
>>          T_ASSERT expr ';'
>>
>>          This means that assert("some code here") will pass assertion
>> causing no error, because strings are no longer treated as code, because
>> eval is evil();
>>
>>          Setting zend.assertions=0 system configuration setting will stop
>> ZEND_ASSRT compilation.
>>
>>          So, we have:
>>
>>          try {
>>                  assert (PHP != JUNK);
>>
>>
>>          } catch(AssertionException $ex) {
>>                  printf("Assertion failed: %s\n", $ex->getMessage());
>>                  printf("Something is horribly wrong ...\n");
>>          }
>>
>>          Better, no ??
>
>
> I like the idea.
> However, there is always the debatte about if a Core feature should throw
> an Exception or generate an error.
> In our current system, they don't throw Exceptions but generate errors.
> Also : someone could use a callback, and then make them throw exceptions if
> he wants to ; the callback on assertion fail, which IMO is a good feature,
> has dissapeared in your patch.
>
> Julien.Pauli
>
Morning Julien,

	That was brought up in IRC yesterday, someone pointed out that 
generators throw exceptions in some places (from an object method, but 
still). So it's not unprecedented, and nobody has provided reason for 
the preference to use errors over exceptions ... however, general case 
aside:

	Throwing exceptions here makes much more sense than errors, and is the 
reason there is no need for callbacks; should you need to control the 
flow of execution or take some action because of a failed assertion you 
can catch the AssertionException and do that without cluttering ini and 
module globals in order to do it.

	In general, of course, an assertion should abort execution, that's a 
bit final for PHP and runs contrary to 
carry-on-executing-no-matter-what, which we like, on the interweb. But, 
should you need to take some action and stop that exception from 
bubbling to the surface you should do that with language constructs 
try/catch rather than dated callbacks, which don't give you the same 
kind of recovery options so easily, they additionally require a new 
scope, a new function entry, module globals for support, and ini 
settings to configure ...

	That being said, I would rather reimplement the ability to invoke a 
callback than scrap the idea all together ... but might we have 
something a bit more PHP5 ??

	assert(
		$expression != false ||
		(CONSTANT_MASK & HAS_BITS),
		function(){ 	
			echo "oh rly?"; }
	);

	I still think it's a bit unnecessary, and this:

	try {
		assert($expression != false ||
			(CONSTANT_MASK & HAS_BITS));

	} catch (AssertionException $ex) {
		echo "oh rly?";
	}
	
	Makes much more sense ... I would rather encourage or even require that 
than reimplement callbacks ... they only seemed to exist to service the 
current implementation.

	In summary then, I think exceptions make more sense than errors and 
callbacks ...

	So what do we think about callbacks and errors now, am I making any 
sense ??

Cheers
Joe