jpackage signing fails with Mac jdk-14.0.1+7

[Adam Carroll]

Using JDK 14.0.1 on the Mac, jpackage fails when signing is requested.
This problem was observed using AdoptOpenJDK.  I reported the problem to
that project and they suggested that  I report the problem here.

Platform:

Mac OS Catalina v10.15.4

Architecture:

x86

Description:

This problem was seen using AdoptOpenJDK 14.0.1+7.

Using the Mac signing option for jpackage ... --mac-sign ... I see the
following error (extra path information removed):

/var/folders/rh/...../HelloFX.app: is already signed

However, if the --mac-sign option is removed, the build works without a
problem.

Reproducing the problem:

I've created a minimal, single-class JavaFX application along with the
necessary scripts to reproduce the problem:
https://github.com/AdamCarroll/jdk14-jpackage-mac

First clone the repo:

$ git clone git at github.com:AdamCarroll/jdk14-jpackage-mac.git

Checkout the tag:

$ git checkout 1.0.0

Run the build (very fast as there's only one class):

$ ./gradlew clean build

Now run the jpackage command with the --mac-sign option as follows (this is
included in the file bin/create-signed-dmg.sh):

$ jpackage \
    --type dmg \
    --module-path 'build/modules' \
    --verbose \
    --add-modules javafx.controls \
    --input 'build/libraries' \
    --dest "build/bundle" \
    --name HelloFX \
    --main-jar 'jdk14-jpackage-mac.jar' \
    --main-class 'demo.HelloFX' \
    --mac-sign

You will now see a long error that includes the following:

/var/folders/rh/...jdk.incubator.jpackage..../HelloFX.app: is already signed
java.io.IOException: Command [codesign, -s, Developer ID Application: Your
Name Here (XXXXXXXXXX), -vvvv,
/var/folders/rh/...jdk.incubator.jpackage.../HelloFX.app] exited with 1 code
at
jdk.incubator.jpackage/jdk.incubator.jpackage.internal.Executor.executeExpectSuccess(Executor.java:73)
at
jdk.incubator.jpackage/jdk.incubator.jpackage.internal.IOUtils.exec(IOUtils.java:179)
at
jdk.incubator.jpackage/jdk.incubator.jpackage.internal.IOUtils.exec(IOUtils.java:150)
...

If you now run the same command but without the --mac-sign option (or
alternatively use the script bin/create-unsigned-dmg.sh), everything works
without problems.

You can find the original issue report to the AdoptOpenJDK repository here:
https://github.com/AdoptOpenJDK/openjdk-build/issues/1718