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To: "Stas Malyshev" <smalyshev@sugarcrm.com>
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Date: Thu, 9 Aug 2012 09:46:49 +0300
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Subject: Re: [PHP-DEV] Error handling brainstorming
From: sv_forums@fmethod.com ("Stan Vass")

> You are either purposefully exaggerating or not doing it right.
>
> if(fileop1() && fileop2() && fileop3()) {
> // do valid stuff
> } else {
> // do error stuff
> }
>
> It's not that hard.

I guess it was my mistake that I simplified my actual code for simplicity's 
sake. Please show me how would my actual code look stuffed in an "if" 
statement:

try {
   $cacheBaseFile = Core\CACHE_PATH . '/Compiled/' . \str_replace('\\', '-', 
$symbolName);

   // The validator checks whether the cache is fresh.
   $cacheIsFresh = include $cacheFileBase . '.val.php';

   // Attempt to load the cache (it should be there if the validator is 
there, unless someone messed with the files).
   if ($cacheIsFresh) {
      $result = include $cacheFileBase . '.main.php';
   } else {
      $this->generateCache($symbolName);
      ...
   }
   return $result;
} catch (IncludeIOError $e) { // One or more of the files were damaged or 
missing.
   ...
}

When you have:

1) comments
2) multiple statements
3) assign variables
4) call functions/methods with long arguments
etc.

...you can't just stuff it in an if (op() && op() && op()) and pretend this 
is in any way a maintainable code style.

>> With exceptions:
>> ----------------
>> try {
>>     fileop1();
>>     fileop2();
>>     fileop3();
>>     normal_actions();
>> } catch (IOException $e) {
>>     exceptional_actions();
>> }
>
> Now imagine fileop1 throws some other exception - note that you have no
> idea which exceptions are there and nothing guarantees you fileop1
> throws only IOException, and by the proposal here, any problem in any
> code whatsoever results in exception now, even if the problem was in
> converting log message to utf-8 while writing some log inside some
> function called by fileop2(). Now your whole app has failed, even though
> you don't really care about that log message at all.

Exceptions aren't about log messages, they're about exceptions - error 
conditions that have to be handled.
If my code above generates another type of exception there are only two 
options:

1) Either I catch that exception because I know how to handle it -or-
2) I don't catch it, and the app should correctly stop right there before 
data damage is done.

I know PHP's model is all messed up, but no one here, I believe, is asking 
about putting non-error log messages in Exceptions. IO failure is an 
exception.

If your IO operation fails, you can't just log it and plow forward 
blissfully without handling the problem.

Stan