RFR: 8252730: jlink does not create reproducible builds on different servers

[Stuart Marks]

On Mon, 14 Sep 2020 20:35:24 GMT, Ian Graves <igraves at openjdk.org> wrote:

> Related to [JDK-8252730 jlink does not create reproducible builds on different
> servers](https://bugs.openjdk.java.net/browse/JDK-8252730). Introduces ordering based on `Archive` module names to
> ensure stable files (and file signatures) across generated JDK images by jlink.

Sorting the Archive instances makes more sense to me than trying to add hashCode/equals to Archive. I note that the
instances added to the ResourcePoolManager are stored in a LinkedHashMap, so the sorted order should be preserved. I'll
defer to Alan and Jim as to whether sorting by module name is the right thing. Additional code comments to follow.

src/jdk.jlink/share/classes/jdk/tools/jlink/internal/ImageFileCreator.java line 274:

> 272:                                     e.getResourcePoolEntryName(), e))
> 273:                             .forEach(resources::add);
> 274:                 });

I'm somewhat allergic to nested forEach plus statement lambdas. I note that the original code mixed an imperative
for-loop with a stream, which was kind of odd; converting to a straight nested for-loop might be reasonable.
Alternatively, the nested forEaches could be converted to a flatMap as follows:

`
        archives.stream()
                .map(Archive::moduleName)
                .sorted()
                .flatMap(mn -> entriesForModule.get(mn).stream()
                               .map(e -> new ArchiveEntryResourcePoolEntry(mn, e.getResourcePoolEntryName(), e)))
                .forEach(resources::add);
`

-------------

PR: https://git.openjdk.java.net/jdk/pull/156