My take on assertions, which I also tried to stick to in Wikibase, is as
follows:
* A failing assertion indicates a "local" error in the code or a bug in PHP;
They should not be used to check preconditions or validate input. That's what
InvalidArgumentException is for (and I wish type hints would trigger that, and
not a "fatal error"). Precondition checks can always fail, never trust the
caller. Assertions are things that should *always* be true.
* Use assertions to check postconditions (and perhaps invariants). That is, use
them to assert that the code in the method (and maybe class) that contains the
assert is correct. Do not use them to enforce caller behavior.
* Use boolean expressions in assertions, not strings. The speed advantage of
strings is not big, since the expression should be a very basic one anyway, and
strings are awkward to read, write, and, as mentioned before, potentially
dangerous, because they are eval()ed.
* The notion of "bailing out" on "fatal errors" is a misguided remnant from the
days when PHP didn't have exceptions. In my mind, assertions should just throw
an (usually unhandled) exception, like Java's AssertionError.
I think if we stick with this, assertions are potentially useful, and harmless
at worst. But if there is consensus that they should not be used anywhere, ever,
we'll remove them. I don't really see how the resulting boiler plate would be
cleaner or safer:
if ( $foo > $bar ) {
throw new OMGWTFError();
}
-- daniel
Am 31.07.2013 00:28, schrieb Tim Starling:
On 31/07/13 07:28, Max Semenik wrote:
I remeber we discussed using asserts and decided they're a bad
idea for WMF-deployed code - yet I see
Warning: assert() [<a href='function.assert'>function.assert</a>]:
Assertion failed in
/usr/local/apache/common-local/php-1.22wmf12/extensions/WikibaseDataModel/DataModel/Claim/Claims.php
on line 291
The original discussion is here:
<http://thread.gmane.org/gmane.science.linguistics.wikipedia.technical/59620>
Judge for yourself.
-- Tim Starling
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