trouble with java -Xpatch

[Martin Buchholz]

The only doc for -Xpatch I can find is

$ java -X |& grep -A2 Xpatch
    -Xpatch:<module>=<file>(:<file>)*
                      Override or augment a module with classes and resources
                      in JAR files or directories

BUT that syntax appears to have no effect, e.g.
if I try
java -Xpatch:java.base=$CLASSES
that seems to have no effect, whatever the value of $CLASSES, and
there is no warning/error if $CLASSES doesn't exist in the filesystem,
which seems like a bug.

Currently
java -Xpatch:$CLASSES
does work, but only if $CLASSES is a directory, not a jar file, which
seems like a bug.

If I have two separate -Xpatch flags, then I get:

$ java -Xpatch:junk -Xpatch:junk -help
Error occurred during initialization of VM
java.lang.ExceptionInInitializerError
at java.lang.module.SystemModuleFinder.<clinit>(java.base/SystemModuleFinder.java:129)
at java.lang.module.ModuleFinder.ofSystem(java.base/ModuleFinder.java:165)
at jdk.internal.module.ModuleBootstrap.boot(java.base/ModuleBootstrap.java:98)
at java.lang.System.initPhase2(java.base/System.java:1916)
Caused by: java.lang.IllegalArgumentException: Unable to parse: junk
at jdk.internal.module.ModulePatcher.throwIAE(java.base/ModulePatcher.java:583)
at jdk.internal.module.ModulePatcher.decodeProperties(java.base/ModulePatcher.java:97)
at jdk.internal.module.ModulePatcher.<clinit>(java.base/ModulePatcher.java:73)
at java.lang.module.SystemModuleFinder.<clinit>(java.base/SystemModuleFinder.java:129)
at java.lang.module.ModuleFinder.ofSystem(java.base/ModuleFinder.java:165)
at jdk.internal.module.ModuleBootstrap.boot(java.base/ModuleBootstrap.java:98)
at java.lang.System.initPhase2(java.base/System.java:1916)

I expect to get "Unable to parse: junk" even with just a single
-Xpatch:junk, but I don't.

I might have filed bugs, but I don't know where.