RFR: 8258117: jar tool sets the time stamp of module-info.class entries to the current time [v9]

[Lance Andersen]

On Wed, 24 Nov 2021 15:04:35 GMT, Jaikiran Pai <jpai at openjdk.org> wrote:

>> The commit here is a potential fix for the issue noted in https://bugs.openjdk.java.net/browse/JDK-8258117.
>> 
>> The change here repurposes an existing internal interface `ModuleInfoEntry` to keep track of the last modified timestamp of a `module-info.class` descriptor.
>> 
>> This commit uses the timestamp of the `module-info.class` on the filesystem to set the time on the `JarEntry`. There are a couple of cases to consider here:
>> 
>> 1. When creating a jar  (using `--create`), we use the source `module-info.class` from the filesystem and then add extended info to it (attributes like packages, module version etc...). In such cases, this patch will use the lastmodified timestamp from the filesystem of `module-info.class` even though we might end up updating/extending/modifying (for example by adding a module version) its content while storing it as a `JarEntry`. 
>> 
>> 2. When updating a jar (using `--update`), this patch will use the lastmodified timestamp of `module-info.class` either from the filesystem or from the source jar's entry (depending on whether a new `module-info.class` is being passed to the command). Here too, it's possible that we might end up changing/modifying/extending the `module-info.class` (for example, changing the module version to a new version) that gets written into the updated jar file, but this patch _won't_ use `System.currentTimeMillis()` even in such cases.
>> 
>> If we do have to track actual changes that might happen to `module-info.class` while extending its info (in `extendedInfoBytes()`) and then decide whether to use current system time as last modified time, then this will require a bigger change and also a discussion on what kind of extending of module-info.class content will require a change to the lastmodifiedtime of that entry.
>
> Jaikiran Pai has updated the pull request incrementally with three additional commits since the last revision:
> 
>  - review suggestion - format code in ModuleInfoEntry to use 4 space indentation
>  - review suggestion - change javadoc to mention module-info.class instead of module descriptor
>  - review suggestion - use if/else instead of ternary operator

Marked as reviewed by lancea (Reviewer).

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PR: https://git.openjdk.java.net/jdk/pull/5486