RFR: 8331051: Add an `@since` checker test for `java.base` module

[Nizar Benalla]

On Fri, 26 Apr 2024 23:24:19 GMT, Jonathan Gibbons <jjg at openjdk.org> wrote:

>> This checker checks the values of the `@since` tag found in the documentation comment for an element against the release in which the element first appeared.
>> 
>> Real since value of an API element is computed as the oldest release in which the given API element was introduced. That is:
>> - for modules, classes and interfaces, the release in which the element with the given qualified name was introduced
>> - for constructors, the release in which the constructor with the given VM descriptor was introduced
>> - for methods and fields, the release in which the given method or field with the given VM descriptor became a member of its enclosing class or interface, whether direct or inherited
>> 
>> Effective since value of an API element is computed as follows:
>> - if the given element has a `@since` tag in its javadoc, it is used
>> - in all other cases, return the effective since value of the enclosing element
>> 
>> The since checker verifies that for every API element, the real since value and the effective since value are the same, and reports an error if they are not.
>> 
>> Preview method are handled as per JEP 12, if `@PreviewFeature` is used consistently going forward then the checker doesn't need to be updated with every release. The checker has explicit knowledge of preview elements that came before `JDK 14` because they weren't marked in a machine understandable way and preview elements that came before `JDK 17` that didn't have `@PreviewFeature`.
>> 
>> Important note : We only check code written since `JDK 9` as the releases used to determine the expected value of `@since` tags are taken from the historical data built into `javac` which only goes back that far
>> 
>> The intial comment at the beginning of `SinceChecker.java` holds more information into the program.
>> 
>> I already have filed issues and fixed some wrong tags like in #18640, #18032, #18030, #18055, #18373, #18954, #18972.
>
> test/jdk/tools/sincechecker/SinceChecker.java line 423:
> 
>> 421:     }
>> 422: 
>> 423:     //these were preview in before the introduction of the @PreviewFeature
> 
> Just curious: where do you find this information?

Used a script to get all the elements with `@Deprecated(forRemoval=true, since=...)`, `@jdk.internal.preview`, `{@preview Associated with ....` in their javadoc.
And then had to cross reference with a document that had all the ids

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PR Review Comment: https://git.openjdk.org/jdk/pull/18934#discussion_r1582899131