RFR: 8321139: jlink's man page does not document the --compress option correctly [v3]

[Jaikiran Pai]

On Thu, 20 Nov 2025 10:51:06 GMT, Ana Maria Mihalceanu <duke at openjdk.org> wrote:

>> This PR looks into aligning the behavior and documentation for `--compress` option and plugin of `jlink`:
>> 
>> - When an user provides `-c {0|1|2}` to `jlink`, then the tool should process it as when receiving `--compress={0|1|2}`. As these values are now deprecated, a warning should be issued to the end user.
>> - When an user provides `-c zip-[0-9]` to `jlink`, then the tool should process it as when receiving `--compress=zip-[0-9]`.
>> - When no compression level is given, meaning the `jlink` command does not contain either `-c` or `--compress` with a value, the default level selected is `zip-6`.
>> - The `--compress` option description reflects above behavior and warns that previous compression levels are deprecated to be removed in a future release.
>> - The `--plugin` option description reflects the implementation behavior and warns that previous compression levels are deprecated to be removed in a future release.
>> 
>> Some implementation details and choices:
>> - While current `jlink` man page states that the tool supports `-c={0|1|2}`, I inspired myself on how `javac` supports the shortened options https://docs.oracle.com/en/java/javase/25/docs/specs/man/javac.html#options.
>> - While `-c 0` and `--compress=0` produce the same compression level as of `zip-0`, I preferred not to tie the new compression level to the old value for the option. I believe that this approach would make it easier/cleaner to remove the code for the deprecated values (when their time comes).
>> - While `-c 2` and `--compress=2` produce the same compression level as of `zip-6`, I preferred not to tie the new compression level to the old value for the option. I believe that this approach would make it easier/cleaner to remove the code for the deprecated values (when their time comes).
>> - As I didn't affect the actual compression implementation, only the options, I tested only how the options are mapped. The actual set and validation of the options was not affected, hence I didn't change those tests.
>
> Ana Maria Mihalceanu has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - Remove extra line.
>  - Align behavior of compression levels to the input received and sync help+documentation messages.

The change overall looks reasonable to me.

Given that we ended up fixing the behaviour of `-c` option in this PR, I think we should rename the JBS issue to something like "jlink's compression plugin doesn't handle -c option correctly". It should then be OK to address the man page and the help text changes as part of this same fix. I believe a CSR will be needed for this change.

My knowledge of this tool is very limited, so please wait for Alan's input before doing the JBS issue change.

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PR Comment: https://git.openjdk.org/jdk/pull/28359#issuecomment-3562228861