RFR: JDK-8200337: Generalize see and link tags for user-defined anchors [v4]

[Jonathan Gibbons]

On Fri, 7 Oct 2022 13:51:23 GMT, Hannes Wallnöfer <hannesw at openjdk.org> wrote:

>> Please review a a new feature to allow `@link`, `@linkplain` and `@see` tags to link to arbitrary URI fragments in the generated documentation (including in auxiliary `doc-files` documentation).
>> 
>> The changes in module `jdk.compiler` are mostly cleanup changes retained from earlier versions of the patch. The current proposed version uses a very simple change in `ReferenceParser` to avoid parsing the member name section of the reference when a non-member fragment is encountered.
>> 
>> The implementation introduces a new form of reference with a double hash mark (`##`) separator. This is a change from the previous implementation which also auto-recognized URI fragments and documentation paths by looking for `-` characters which are not allowed in member names. This feature was removed upon further consideration because it makes the feature more complex and less recognizable.
>>  
>> Links to auxiliary documentation files follow the same rules. They are recognized by looking for `/` characters in the fragment name. This means that ordinary `id` attribute values must not contain `/`, while auxiliary file paths must contain a `/` character. Both restrictions should be easy to sustain.
>> 
>> One thing that is difficult for this feature is to provide a good link label if no label is supplied in the tag. In contrast to program element names a fragment name does usually not make a good human readable name. The solution is to use the fragment name as default label text. I expect that the feature will usually be used with a user provided label.
>
> Hannes Wallnöfer has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Remove aux doc file reference feature

(repeating? after first message was lost...?)

I primarily reviewed the `DocCommentParser` level of the code.

Removing the `allowMember` parameter from the `reference` method seems like a retrograde step, since there are places where the method is called that require a specific kind of reference, such as requiring a type name after `@throws`.

If anything you should honor the `TODO` that you deleted there, and upgrade the `boolean allowMember` parameter into some sort of enum set that allows a caller to specify the kinds of reference that are acceptable in any given syntactic position.  After all, the new `##` syntax should only be permitted in `@see` and `{@link}` nodes.

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PR: https://git.openjdk.org/jdk/pull/10395