The major problem with unchecked exceptions is that it is not class
consumer business.
What do you say when someone throws SomethingIsBrokenInsideOfMe to you? I'd
say "hey, take a vacation, fix yourself, you look unhealthy". Is it not my
business what exactly is broken (leg or arm, whatever, it doesn't help to
fix my issue). But it is fair enough if library throws YouAreWrong
exception in my face when I'm screwed up.
When you make a typo in your Container implementation, it could fail with
something like \TypeError. It is "unhappy-path", isn't it? Is
it MisconfiguredServiceException? I don't think so. What do you do then?
You go and fix your implementation. What happens if configuration is
broken? You go and fix it as well. I don't see much difference here.
MisconfiguredServiceException for me is an illusory solution for
"unhappy-path". You can't trust it. What does it exactly mean? What if you
make a syntax typo in your PHP configuration (with arrays, let's say),
should it raise the MisconfiguredServiceException? Or it should bubble up
\ParseError? I mean, it is more like ConfigurationIsTotallyScrewedUp rather
than simple MisconfiguredService. It's vague exception that means
"something is wrong with *them*". I'd rather catch ALL other
(non-NotFoundException) exceptions if I want to avoid program crash for
some reason. I can trust \Exception (or even \Throwable). The meaning is
simply same: "something is wrong with them" and I don't really care what
exactly is.
Can you please provide real-life example when you want to catch
MisconfiguredServiceException (excepting "I want to log it differently",
because it doesn't look real-life, honestly; and it is too universal answer
for any kind of exceptions)?
On Monday, November 7, 2016 at 5:27:58 PM UTC+3, Larry Garfield wrote:
>
> Container nesting is part of the spec, and a stated goal of the spec, so
> it's a valid use case to consider.
>
> True, there are many different ways that things can break. Consistent and
> constructive handling of the not-happy path is a critical part of spec
> development. See also: HTML5, the majority of which is not new stuff but
> standardizing the many different ways that browsers used to handle badly
> formed HTML. It's a total mess because the unhappy path was never
> well-defined, so everyone did it differently, so code broke in a variety of
> inconsistent ways. My issue is that "throw anything other than X" is not a
> consistent and constructive handling of the non-happy path.
>
> The biggest distinction I would draw would be between "you asked for
> something that's not there" and "you asked for something that's broken".
> Those are very different things; one implies I screwed up, the other
> implies the configurer screwed up. I can see the argument for not
> specifying a separate exception for every possible way that the requested
> service is broken (there are many, that's true), but a clear distinction
> between those two broad categories ("missing" and "broken") seems like a
> much better baseline.
>
> In that case, I would revise my ask to defining two exceptions:
>
> * NotFoundException extends ContainerExceptionInterface (thrown if the
> requested service isn't defined anywhere)
> * MisconfiguredServiceException extends ContainerExceptionInterface
> (thrown if the requested service is defined, but for whatever reason can't
> be instantiated)
>
> And implementers are free to subclass the latter if they choose, but must
> still have that exception flag on them. (I'm flexible on the name, the one
> I have there is likely not the best name.)
>
> --Larry Garfield
>
> On 11/05/2016 12:59 PM, Daniel Plainview wrote:
>
> > A situation of "if your child container throws exception X, you're
> required to catch it and turn it into anything that's not X but is still Y"
> seems needlessly convoluted
>
> You did it by introducing "child container", Container contract doesn't
> have any child containers, this contract is very simple
> and straightforward. By saying about child containers, you mean that you
> know how internals of the Container work, you know about "child
> containers", but you shouldn't care about it when you want to use Container.
>
> > but doesn't provide me as a developer sufficient debug information. I'd
> potentially want to log differently depending on which exception it is, but
> I can't do that if I have no idea what the second exception is going to be;
> I just know what it's *not* going to be, which means I'd need a
> Pokemon-catch if I wanted to log it. That's what I am not comfortable with.
>
> I asked you above, what do you think about
> DependencyArgumentTypeMismatchException, MissingRequiredArgumentException
> and many other exceptions, what makes them less important than
> DependencyNotFoundException? They are all about wrong configuration (or
> similar issues that indicates of internal problems of Container, not user's
> failure).
>
> I mean, you can say that "I'd potentially want to log differenty
> DependencyArgumentTypeMismatchException and
> MissingRequiredArgumentException, but I don't know how to catch them".
> There are millions of reasons why container can be broken, after all, you
> can't predict them all.
>
> DependencyNotFoundException is unchecked, because it is not client's
> problem, but internal issue of Container itself. Service does exist, but
> configuration is wrong, client has nothing to do with it, there is no sense
> to reflect it in the interface.
>
> On Saturday, November 5, 2016 at 3:38:06 AM UTC+3, Larry Garfield wrote:
>>
>> On 11/04/2016 06:27 AM, David Négrier wrote:
>>
>> I'll try an analogy with Java.
>>
>> In Java, there is a difference between checked and unchecked exceptions.
>> Checked exceptions are the exceptions that should be catched by the user.
>> Unchecked exceptions are the exceptions for which it makes no sense to
>> catch them. There is no reason to catch an "unchecked exception" because
>> there is no way the user can provide an interesting alternative behaviour
>> in the catch statement. So unchecked exception should essentially always
>> bubble up all the way to the top of the application and trigger an
>> exception middleware.
>>
>> For PSR-11, we deemed that the NotFoundExceptionInterface was a checked
>> exception (because if the container does not contain the entry you are
>> looking for, the user can maybe try an alternative behaviour like looking
>> for an alias or creating a default entry).
>> We also deemed that the DependencyNotFoundExceptionInterface was an
>> unchecked exception (because it means the container is poorly configured
>> and there is little to do about it except display an error message).
>>
>> Finally, we think that checked exceptions should be part of a PSR while
>> unchecked exceptions should be out of any PSR (because there is no need to
>> standardize an exception if you don't need to catch it).
>>
>> Of course, there is no absolute truth here. We could decide that the
>> NotFoundExceptionInterface should be "unchecked" (because you can always
>> call "has" before "get" so there is no reason this exception should be
>> catched). Also, since it boils down to "what valid use case can I have to
>> catch a DependencyNotFoundExceptionInterface?", we could also find a valid
>> use case for catching DependencyNotFoundExceptionInterface and decide it
>> should be part of the PSR. But so far, a quick survey of frameworks out
>> there has shown that no-one ever catches the "dependency not found
>> exceptions".
>>
>> Also, Larry, you say:
>>
>>
>>
>>
>>
>>
>>
>>
>>
>> *... based on the spec alone (no metadoc, no GitHub threads) the
>> following would be legal: try { $c1->get('a'); } catch
>> (NotFoundExceptionInterface $e) { print $e->getMessage(); // prints
>> "Service 'b' not found" } *
>> This is not completely true. The spec states that:
>>
>>
>> *A call to get can trigger additional calls to get (to fetch the
>> dependencies). If one of those dependencies is missing, the
>> NotFoundExceptionInterface triggered by the inner get call SHOULD NOT
>> bubble out. Instead, it should be wrapped in an exception implementing the
>> ContainerExceptionInterface that does not implement the
>> NotFoundExceptionInterface. *
>> So your code example is only valid if the container decides not to follow
>> the recommendation (we used "SHOULD NOT" instead of "MUST NOT" to cope with
>> existing containers). Of course, we could also strengthen the wording and
>> write: *If one of those dependencies is missing, the
>> NotFoundExceptionInterface triggered by the inner get call MUST NOT bubble
>> out.*
>> This way, your code sample would be illegal (but it would be harder for
>> existing containers to implement PSR-11). I have no strong opinion about
>> the "SHOULD NOT" vs "MUST NOT" idea so far. Your comments are welcome.
>>
>> ++
>> David.
>>
>>
>> See, I would disagree with dependency-not-found being an unchecked
>> exception. I think that's the fundamental difference. A situation of "if
>> your child container throws exception X, you're required to catch it and
>> turn it into anything that's not X but is still Y" seems needlessly
>> convoluted, but doesn't provide me as a developer sufficient debug
>> information. I'd potentially want to log differently depending on which
>> exception it is, but I can't do that if I have no idea what the second
>> exception is going to be; I just know what it's *not* going to be, which
>> means I'd need a Pokemon-catch if I wanted to log it. That's what I am not
>> comfortable with.
>>
>> I am generally very skeptical about SHOULD, and favor MUST in nearly all
>> cases by default. SHOULD should be read as "you're allowed to be
>> incompatible here", which is a statement a spec should make as rarely as
>> possible.
>>
>> --Larry Garfield
>>
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