Unnecessary compile with private-B-change-removes-B-to-A-dep.patch

[guw]

Thanks to @rsalvador we have a case of an unnecessary compilation which is no longer a cache hit due to a classpath change.

./script.sh private-B-change-removes-B-to-A-dep
...
INFO: 4 processes: 1 internal, 1 darwin-sandbox, 2 worker.

and the explain log:

Executing action 'Building libB.jar (1 source file)': One of the files has changed.
Executing action 'Extracting interface for jar bazel-out/darwin_x86_64-fastbuild/bin/libB.jar': One of the files has changed.
Executing action 'Building libC.jar (1 source file)': One of the files has changed.

So C is being rebuild although the ijar of B does not change.

[fmeum]

@guw I see that this disables Java header compilation in the .bazelrc. With --java_header_compilation, I get the expected outcome with no unnecessary rebuild:

INFO: 3 processes: 1 internal, 1 linux-sandbox, 1 worker.

Why do you disable Java header compilation? It is pretty much required with --experimental_java_classpath=bazel as it provides the list of "API deps" for a given target.

[guw]

That's quite surprising, isn't it? Only directly declared deps should be responsible for re-compilation and not changes in the transitive list.

The header compilation had to be disabled because it's too expensive (much longer build times) and it's broken.