Custom attributes (again)

[Alex Rønne Petersen]

On 06-04-2012 09:32, Walter Bright wrote:
> On 4/6/2012 12:17 AM, Kapps wrote:
>> I like it for the most part. One thing I'd like to see is placing
>> multiple
>> attributes both by using multiple @attr()'s, and by using comma separated
>> identifier/expression pairs inside a single @attr. In other words, the
>> following
>> two declarations would be identical.
>>
>> @attr(Description = "Blah", ReadOnly)
>> int ID;
>>
>> @attr(Description = "Blah")
>> @attr(ReadOnly)
>> int ID;
>
> Yes, that makes sense.
>
>> My only concerns:
>>
>> First, @attr() is a little verbose / not exactly pretty. This isn't
>> really a big
>> issue, since attributes aren't exactly piled on and it makes it easy
>> to tell
>> what's going on. It is a little uglier than in other languages however.
>
> Could do:
>
> [[name = value]]
>
> I suppose. Not sure what's better.
>
>
>> Secondly, from what I can tell it's an arbitrary key value combo. What
>> would
>> happen if you're working on a larger project and two unrelated
>> libraries try to
>> use the same attribute name to mean different things? With the module
>> system
>> this issue doesn't exist since you have to import it and can
>> selectively/privately do so, but from what I understand the method you're
>> proposing doesn't declare the attribute itself at all. Am I just
>> misunderstanding this part?
>
> Good question. I don't have experience using attributes, so I don't know
> if this would be a problem. Keep in mind that the attribute lookup will
> only be done for a particular symbol, there won't be any global lookup.

It actually can be a problem. In .NET land, there are many attributes 
across many projects (and even in the framework itself) with the same 
names. It turns out that regular namespace lookup rules alleviate this 
problem.

-- 
- Alex