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Date: Mon, 21 Oct 2019 22:59:03 +0100
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Subject: Re: [PHP-DEV] Reclassifying some PHP functions warning as exceptions
From: rowan.collins@gmail.com (Rowan Tommins)

On 21/10/2019 21:38, Benjamin Morel wrote:
> Sure, you can do without exceptions. I think what you're suggesting is 
> similar to Go's error handling. But PHP at some point decided in 
> favour of exceptions, so it would be logical to pursue in that direction.


I didn't say "do without exceptions", I said "use exceptions when 
they're the right tool, and other tools at other times".


> I would classify most, if not all, filesystem-related functions as 
> mostly "yes, do stop execution by default when something fails". So 
> this is, as well, in favour of exceptions.


You've backed that up with exactly one example function, and immediately 
concede a case where you might want a non-exception flow. Here are a 
handful more examples off the top of my head:

* Attempt to atomically lock and open file, returning either a file 
handle or a "could not lock" status.
* Attempt to read from a file, terminate loop when the file handle 
reaches EOF.
* Attempt to delete file, ignore if it doesn't exist.

All of these are candidates for returning false, or an error code, or an 
object in a particular status. They could be handled with exceptions, 
but that would force common patterns to use exceptions for flow control, 
which is generally seen as a "bad smell".


> Handling each and every error manually by using the return value 
> requires a lot of discipline, which could be a very steep learning 
> curve for PHP developers used to a fast prototyping language.


Again, I am not saying that every function should have a complex 
error-handling system. It may well be sensible to have a function for 
"open file, I don't expect anything to go wrong" which throws an 
exception, and a separate one for "try to open file, and report the 
result without ever triggering an exception". That's the point of 
designing a new API, to work out what the use cases are, and cater for 
them in a clean way.


Regards,

-- 
Rowan Tommins (né Collins)
[IMSoP]