JDK 16 RFR of JDK-8248983: Add Name.isEmpty

[forax at univ-mlv.fr]

----- Mail original -----
> De: "joe darcy" <joe.darcy at oracle.com>
> À: "Remi Forax" <forax at univ-mlv.fr>
> Cc: "compiler-dev" <compiler-dev at openjdk.java.net>
> Envoyé: Mercredi 8 Juillet 2020 18:23:21
> Objet: Re: JDK 16 RFR of JDK-8248983: Add Name.isEmpty

> Hi Remi,
> 
> The value of the method is to provide a reference point within the
> javax.lang.model API for the "empty name" concept. The goal for the code
> in the body of Name.isEmpty is to have as little as possible, preferably
> just delegating to CharSequence.isEmpty. I'd prefer to have the empty
> name links point to the method Name.isEmpty rather than
> CharSequence.isEmpty, hence defining a minimal Name.isEmpty method
> within the API.

I can buy that the concept of empty name is important, following what you are saying, length() should be re-abstracted for the exact same reason.
I think i prefer to follow the current implementation of Name that explain the concept of empty name in the top level javadoc of Name, and fix the sentence "An empty Name has a length of zero." to mention isEmpty.

> 
> HTH,
> 
> -Joe

Rémi

> 
> On 7/8/2020 5:15 AM, Remi Forax wrote:
>> HI Joe,
>> I don't understand the value that this method provides,
>> because either the JDK 15 is the bootstrap JDK and in this case, this code is
>> useless because CharSequence.isEmpty() already provides the right behavior,
>> or you don't and it will not compile.
>>
>> So either you write it to delegate to length() so you are not dependent of JDK
>> 15 being the bootstrap JDK or you do nothing and you will get isEmpty() for
>> free when the JDK 15 will be the bootstrap JDK.
>>
>> public interface Name extends CharSequence {
>>       /**
>> +     * Returns {@code true} if this is an empty name with a length of
>> +     * zero; returns {@code false} otherwise.
>> +     * @return {@code true} for an empty name and {@code false} otherwise.
>> +     *
>> +     * @since 16
>> +     */
>> +    default boolean isEmpty() {
>> +        return length() == 0;
>> +    }
>>
>> regards,
>> Rémi
>>
>> ----- Mail original -----
>>> De: "joe darcy" <joe.darcy at oracle.com>
>>> À: "compiler-dev" <compiler-dev at openjdk.java.net>
>>> Envoyé: Mercredi 8 Juillet 2020 04:23:32
>>> Objet: JDK 16 RFR of JDK-8248983: Add Name.isEmpty
>>> Hello,
>>>
>>> Please review the webev and CSR for
>>>
>>>      JDK-8248983: Add Name.isEmpty
>>>      CSR: https://bugs.openjdk.java.net/browse/JDK-8249005
>>>      webrev: http://cr.openjdk.java.net/~darcy/8248983.0/
>>>
>>> In its current form, this fix can only be pushed *after* the minimum
>>> boot JDK in the JDK 16 build is updated to JDK 15. Otherwise, the
>>> default method on CharSequence is not necessarily present.
>>>
>>> To be pushed earlier, the default method on Name would need to be
>>> changed to host an implementation that didn't delegate to
>>> CharSequence.isEmpty. It would not be difficult to take that route
>>> instead with a follow-up bug to change the implementation of the default
>>> method later.
>>>
>>> Thanks,
>>>
> >> -Joe