[bv-dev] Value extraction open issue #13 and #14: Path and nodes

[Gunnar Morling]

Hi Michael,

The names of nodes in property paths have no influence on method
interpolation. They are additional information contained (besides the
message) in constraint violations.

But your hint on relying on the index is a good one: we may represent
constrained type uses with the name *and* index, just as we do it for
ParameterNode in BV 1.1.

--Gunnar


2017-02-22 18:26 GMT+01:00 Michael Nascimento <misterm at gmail.com>:
> Gunnar,
>
> Maybe I'm missing the point here, but as far as I understand, names added to
> the paths will be significant - for instance, it will influence how messages
> will end up being formatted, because keys will now depend on this additional
> information, right? If this is wrong, then disregard what I wrote below
> because it's based on that assumption.
>
> When you rename a property or a class name, client code will very likely
> fail to compile. You're releasing an incompatible change - you probably need
> to bump your major version in some cases and write thorough release notes in
> order to do that. Now, we're saying that to BeanValidation - and so far, in
> JCP standards, the only one AFAIK -, type parameter *names* are relevant. If
> you rename one, your code will compile but you might end up having a runtime
> exception or a poorly formatted error message because of that, unless you
> explicitly test them for type parameter name change - the only change that
> will not break other parts of your code. Whereas if you really on order, a
> change either breaks compilation or completely changes the semantics of
> existing code and has to follow the incompatible change process.
>
> But, as I said, what I said above is only valid if the names are
> significant, i.e., used somewhere else in a meaningful way.
>
> Regards,
> Michael
>
> On Wed, Feb 22, 2017 at 2:13 PM, Gunnar Morling <gunnar at hibernate.org>
> wrote:
>>
>> > Looks bad, type parameter names in Java are considered documentation and
>> > not
>> > something you cannot change during class evolution. For Map, it won't
>> > ever
>> > change, but for other domain classes, it can change.
>>
>> Property paths reflect on a model in a given state. If your model
>> evolves, e.g. because you rename a bean property, paths obtained
>> previously may not match any element in the model's current state
>> anymore.
>>
>> I.e. I'm failing to see the how the situation is fundamentally
>> different for type parameters?
>>
>> 2017-02-22 17:46 GMT+01:00 Michael Nascimento <misterm at gmail.com>:
>> > On Wed, Feb 22, 2017 at 1:10 PM, Guillaume Smet
>> > <guillaume.smet at gmail.com>
>> > wrote:
>> >>
>> >> = 1. Type parameter information
>> >>
>> >> == 1.1 Should we add the type parameter to the node?
>> >>
>> >> Assume the example of a map:
>> >> private Map<@Valid City (1), @Valid Statistics (2)> map;
>> >>
>> >> With the current way of doing things, you end up with the following
>> >> paths:
>> >> (1) (name = map, type = PROPERTY) -> (name = name, type = PROPERTY,
>> >> isInIterable = true, key = city)
>> >> (2) (name = map, type = PROPERTY) -> (name = count, type = PROPERTY,
>> >> isInIterable = true, key = city)
>> >>
>> >> So you wouldn't be able to differentiate if the violations is coming
>> >> from
>> >> City or Statistics.
>> >>
>> >> One of the ideas we had is to integrate the TypeVariable<?> type
>> >> parameter
>> >> info into the last node. In the case of (1), you would have 2 nodes:
>> >> (1) (name = map, type = PROPERTY) -> (name = name, type = PROPERTY,
>> >> isInIterable = true, key = city, typeParameter = K)
>> >> (2) (name = map, type = PROPERTY) -> (name = count, type = PROPERTY,
>> >> isInIterable = true, key = city, typeParameter = V)
>> >>
>> >> WDYT?
>> >
>> >
>> > Looks bad, type parameter names in Java are considered documentation and
>> > not
>> > something you cannot change during class evolution. For Map, it won't
>> > ever
>> > change, but for other domain classes, it can change.
>> >
>> > Type parameter *order*, though, cannot change without change meaning, so
>> > that's the best option we have left :-(
>> >
>> >>
>> >> == 1.2 If we add this information, what should it be?
>> >>
>> >> At first, Gunnar thought about using java.lang.reflect.TypeVariable for
>> >> this type parameter information but we have an issue with it: it is not
>> >> serializable and the path is supposed to be.
>> >>
>> >> Thus we need to either use a String with the name of the type parameter
>> >> or
>> >> introduce our own serializable structure.
>> >
>> >
>> > Introduce a serializable structure. :-(
>> >
>> >> What's your take on this? If we go the structure route, which
>> >> information
>> >> should this structure contain apart from the name?
>> >> java.lang.reflect.TypeVariable also has the generic declaration
>> >> information.
>> >>
>> >> Do you foresee issues if we are not using
>> >> java.lang.reflect.TypeVariable?
>> >> Typically it would be harder to do additional reflection things.
>> >
>> >
>> > Yeah, as the generics model evolve, we might paint ourselves in the
>> > corner.
>> >
>> >> = 2. Type argument constraints
>> >>
>> >> So, the discussion above also applies to type argument constraints but
>> >> there are some specific questions for them.
>> >>
>> >> == 2.1 New node type
>> >>
>> >> Type argument constraints cover the following case, ZipCode being a
>> >> constraint:
>> >> Map<@ZipCode String, String> map;
>> >>
>> >> In this case, we envision the following node structure (assuming we
>> >> would
>> >> add the typeParameter discussed in 1.1):
>> >> (name = map, type = property) -> (name = '<map key>', type =
>> >> TYPE_ARGUMENT, isInIterable = true, key = myKey, typeParameter = K)
>> >>
>> >> TYPE_ARGUMENT is a new type introduced in javax.validation.ElementKind.
>> >>
>> >> Does it make sense?
>> >
>> >
>> > My answer from above applies here as well.
>> >
>> >> == 2.2 Default node names
>> >>
>> >> The default extractors define the following node names for the added
>> >> TYPE_ARGUMENT node:
>> >> - arrays and Iterables (List included): <iterable element>
>> >> - Map key: <map key>
>> >> - Map value: <map value>
>> >>
>> >> This is similar to the nodes we created for "<return value>" or
>> >> "<cross-parameter>" constraints.
>> >>
>> >> Question: should they have a node name? should it be the type parameter
>> >> name instead (so E or K or V for instance)?
>> >>
>> >> Note that this might have consequences in the string representation we
>> >> will discuss later.
>> >
>> >
>> > If they must have a name, it will probably have to be named after the
>> > types
>> > they apply to and type parameter order :-(
>> >
>> >>
>> >> == 2.3 Optional and ObservableValue
>> >>
>> >> In these 2 cases, we won't append a node.
>> >>
>> >> Note that while in the ObservableValue case, it might feel more natural
>> >> as
>> >> the constraint will probably be used like:
>> >> @NotBlank StringProperty property;
>> >> to apply a NotBlank constraint on the wrapped value so it's rather
>> >> logical
>> >> to not have a node.
>> >>
>> >> Just to be clear, for Optional, on the other hand, with our proposal,
>> >> we
>> >> won't have a node whereas the code looks like:
>> >> Optional<@NotBlank String> optional;
>> >
>> >
>> > Couldn't quite understand what comments I could make about it, so ok :-)
>> >>
>> >>
>> >> = 3 String representation
>> >>
>> >>
>> >> Note: this is implementation specific but we thought it might be
>> >> interesting to discuss it here anyway.
>> >
>> >
>> > Sorry, too many nuances and I don't have a strong opinion here.
>> >
>> > Regards,
>> > Michael
>> >
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