Rasmus Lerdorf wrote:
On 09/01/2012 05:44 PM, Gustavo Lopes wrote:
More importantly, there is no other satisfactory solution (except a
fatal error). foreach has no return value, so it has no other way to
signal a failure. If we used a notice or a warning here what would
happen is that code that used generators with an invalid state would,
except for the notice, work as if it had been given an empty iterator.
Put another way, it would fail with only a notice, and continue. That is
a far more serious problem. In other circumstances where we emit
warnings, we usually have a return value the caller can check for error
conditions.
This is the real question here. It actually isn't about Exceptions at
all. It is whether trying to iterate a closed generator should be a
fatal error that breaks script execution right then and there. Whether
that is done as an exception or a fatal error isn't actually all that
relevant since the end result will be the same for most people. If
everyone is in agreement that this should be a fatal error (I don't
personally get why it has to be fatal) then lets just make it a fatal
error and when we come up with a decent proposal for turning recoverable
fatals into exceptions language-wide we can revisit this. And this might
even be in the same release, so...
Finally I'm understanding what my problem is with a lot of this stuff.
I kept looking at this and trying to understand exactly WHAT the flow through
the code is. The 'magic' processing of generators is hiding away exactly where
the source of a problem is. Showing me the code that is carrying out the
processing, rewind, next etc ... at lease allows me to understand just what is
throwing a problem when it happens - and handling the error! And yes an
exception that gives a accurate error report is the only way of handling that
without the visible code steps to error against? So we are back to the
fundamental problem of how does one HANDLE that exception in an environment
where they are currently only used in limited specific actions ... which may
also be wrong! ...
I prefer to code for and capture errors, so if the file does not exist I check
for that and give the user a suitable warning. If I'm iterating a file and the
read does not complete becuase of an OS read fault I like to capture that state
and handle it. I can accept generators IF I can bail out with a suitable error
when I need to, but exceptions are there simply because no one bothered to
handle the real error? The work flow has been so screwed up that the only way
out is to crash?
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