Re: [aspectj-users] Type expression matching annotation values: String m

[Matthew Adams <matthew@xxxxxxxxxxxxxxx>]

Hi Archie,

I didn't see your message before my last reply.  I really could go with either (a) or (b), but I feel more invested in (b).  I can't speak to the difficulty of implementation of either strategy -- the AspectJ team would have to comment.

While the Java familiarity afforded by (a) is appealing, the verbosity is a turn-off for me.  AspectJ pointcuts already are very terse and a bit cryptic for the uninitiated, so I'm not afraid of just continuing down that road with (b).

Check out my suggestions and please comment with your thoughts.

-matthew

On Fri, Apr 26, 2013 at 10:19 AM, Archie Cobbs <archie@xxxxxxxxxxxx> wrote:

Jumping in to this discussion, feel free to kick me out... :)

Seems like there are two overall strategies here: (a) ad hoc syntax and (b) generic java _expression_ syntax.

Option (a) is what Matthew is suggesting... takes a lot more work, gives more flexibility. And the answer to the "member of array" question just falls out if you choose option (a), e.g. @Foo(Arrays.asList(value).contains(1)).

If you choose option (b) then not only do we have to invent a bunch of new, custom syntax, there will be an endless round of bike-shed arguments about what that syntax ought to be. But (b) is probably a lot more expedient (especially if the project maintainers just dictate whatever syntax they care to implement :)

So I think the first question that should be answered before getting into all the details is: (a) or (b) ?

-Archie

On Fri, Apr 26, 2013 at 10:02 AM, Andy Clement <andrew.clement@xxxxxxxxx> wrote:

I think that would be great, and would provide a lot of flexibility - but it is quite a lot of work... Most cycles are going to get consumed on supporting Java 8 for the next little while.  I'm sure when you start thinking about type annotations (jsr308) you are going to come up with a million new AspectJ use cases...

For strings I might be happier with using a regex of some kind rather than getting into what methods are or are not allowed.  

@Foo(value =~ "/^goo.*/")

For numbers the usual set of operators seem ok.  I'm still waiting for someone to tell me the best operator for that 'member of array' construct we were talking about previously:

@Foo({1,2,3})

declare @type: @Foo(value ???? 1): @ContainsOne;

cheers,

Andy

On 25 April 2013 20:08, Matthew Adams <matthew@xxxxxxxxxxxxxxx> wrote:

So as I've been kicking around some of the type _expression_ enhancements, in
particular, https://bugs.eclipse.org/bugs/show_bug.cgi?id=405016, it
occurred to me that, IMHO, there should be a limited type _expression_ syntax
for matching annotation values.

For example, consider annotation values of type String.  It would be nice to
match case sensitively, insensitively, or even match a regex.  The syntax
for that could look something like the following type _expression_ examples.
Given

public @interface Foo { String value(); }

these would be allowed:

(@Foo(value = "goo") *)
(@Foo(value.equals("goo")) *) // same as above
(@Foo(value.equalsIgnoreCase("goo")) *)
(@Foo(value.startsWith("goo")) *)
(@Foo(value.endsWith("goo")) *)
(@Foo(value.matches("go{2}")) *)
(@Foo(value.trim().length() > 0) *)
...

Any appropriate method or _expression_ that returns boolean seems supportable.

As for numeric types (primitives & wrappers), given

public @interface Bar { int value(); }

these would be allowable:

(@Bar(value > 10) *)
(@Bar(value >= 0 && value < 10) *)
(@Bar(value % 2 == 0) *)
...

Since these type expressions are evaluatable statically (since all
annotation values must be constants), this seems fully validatable at
compile time.

Thoughts?

-matthew



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