[cdi-dev] Challenge TCK test for indirect specialization rules

[Jozef Hartinger]

On 06/03/2014 11:48 AM, Matus Abaffy wrote:
> If the intention was not to ignore the beans in-between, then the rule for indirect specialization seems quite redundant to me.

The way indirect specialization is defined in the spec is equivalent to 
saying that "specialization" relation is transitive. Having

A specializes B
and
B specializes C

that means that also
"A specializes C"
holds true.

I agree that when looking at qualifiers and name only, this "A 
specializes C" relation may seem redundant. Relations "A specializes B" 
and "B specializes C" themselves guarantee
that B contains all the qualifiers of C, A contains all the qualifiers 
of B (and thus also those from C).

However, there are other parts of the specification for which the fact 
that both "A specializes B" and "A specializes C" hold true is 
important. For example, take section 5.1.2.
It says:

"A bean is said to be enabled if it is not specialized by any other 
enabled bean".

Now it makes a difference whether we consider specialization transitive 
(A specializes C relation exists) or not as it influences whether C ends 
up being enabled or not.

Transitive case:
Both B and C are specialized by A and thus only A remains enabled.

Non-transitive case:
A is enabled. B is specialized by A this B is not enabled. C is only 
specialized by B, which is *not enabled* thus C remains enabled. Now 
having both A and C enabled at the same time is clearly wrong and goes 
against the whole purpose of specialization. Instead of replacing C with 
A we end up we both beans enabled.

I think there is no doubt now that non-transitive specialization does 
not fit the CDI spec. In addition, I hope this makes it clear why 
transitivity of specialization is not redundant.

Jozef