Guy Brand created MNG-7161:
------------------------------
Summary: Error thrown during uninstalling of JAnsi
Key: MNG-7161
URL: https://issues.apache.org/jira/browse/MNG-7161
Project: Maven
Issue Type: Bug
Affects Versions: 4.0.x-candidate, 4.0.0, 4.0.0-alpha-1
Reporter: Guy Brand
Our integration tests stopped working after we started to test with a Maven
{{4.0.0-alpha-1}} nightly which included this commit:
[https://github.com/apache/maven/commit/195fb626a9a4e5a0774f779b6d8da1cb9ef38468#diff-9c5fb3d1b7e3b0f54bc5c4182965c4fe1f9023d449017cece3005d3f90e8e4d8R310-R317]
In this commit the {{maven-shared-utils}} and the {{jansi}} dependencies are
being upgraded. When we then run our integration tests we get the following
null pointer exception:
{code:java}
java.lang.NullPointerException
at org.fusesource.jansi.AnsiPrintStream.uninstall(AnsiPrintStream.java:79)
at org.fusesource.jansi.AnsiConsole.systemUninstall(AnsiConsole.java:524)
at
org.apache.maven.shared.utils.logging.MessageUtils.doSystemUninstall(MessageUtils.java:101)
at
org.apache.maven.shared.utils.logging.MessageUtils.systemUninstall(MessageUtils.java:80)
at org.apache.maven.cli.MavenCli.main(MavenCli.java:203)
at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native
Method)
at
java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
at
java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.base/java.lang.reflect.Method.invoke(Method.java:566)
at
org.codehaus.plexus.classworlds.launcher.Launcher.launchEnhanced(Launcher.java:282)
at org.codehaus.plexus.classworlds.launcher.Launcher.launch(Launcher.java:225)
at
org.codehaus.plexus.classworlds.launcher.Launcher.mainWithExitCode(Launcher.java:406)
at org.codehaus.plexus.classworlds.launcher.Launcher.main(Launcher.java:347)
{code}
We debugged this and [these
changes|https://github.com/fusesource/jansi/commit/63bd892b2bdfc253ec119a57bdd42df5e80fd859#diff-d59db8655d9ae2d11948e2b411c34fc9e8513f29065d82c978d7128dafbe3bafR414-R420]
in JAnsi introduced in the above upgraded version, is the source of the
exception. The NPE is caused because the {{out}} reference is {{null}} at the
time it wants to uninstall the {{AnsiOutputStream}}. This reference is nulled
because we use the Plexus interactivity library which [disposes the
{{DefaultOutputHandler}}|https://github.com/codehaus-plexus/plexus-interactivity/blob/master/plexus-interactivity-api/src/main/java/org/codehaus/plexus/components/interactivity/DefaultOutputHandler.java#L51-L54]
on the tear down of Plexus, in which the {{System.out}} reference will be
closed which is in fact the {{out}} reference of the {{AnsiConsole (}}JAnsi
will be[ initialized
before|https://github.com/apache/maven/blob/3e917677e484067b853eaa4a6de44ebcf5a988de/maven-embedder/src/main/java/org/apache/maven/cli/MavenCli.java#L200]
the Plexus container). This happens
[here|https://github.com/apache/maven/blob/3e917677e484067b853eaa4a6de44ebcf5a988de/maven-embedder/src/main/java/org/apache/maven/cli/MavenCli.java#L202],
so before JAnsi will be uninstalled in
[here|https://github.com/apache/maven/blob/3e917677e484067b853eaa4a6de44ebcf5a988de/maven-embedder/src/main/java/org/apache/maven/cli/MavenCli.java#L203].
There are two options to solve this:
1. Report this to JAnsi such that they catch this valid use case and do not
throw as this worked without any exceptions in older versions.
2. Fix the {{MessageUtils#doSystemUninstall()}} and catch all exceptions and
swallow them, as if it can't uninstall it, then Maven itself is not capable of
fixing this state either. This is already done in a similar way
[here|https://github.com/apache/maven-shared-utils/blob/17091d82508deb9b7067f3434ba16f660ffc5023/src/main/java/org/apache/maven/shared/utils/logging/MessageUtils.java#L85-L92]
for removing the shutdown hook.
Our proposal is to do #2 which would make Maven itself resilient to such use
cases as there are other extensions/plugin out there which also retrieve a
reference for the system output streams and therefore they would fail with
Maven 4.0.0. This would also make this part future proof, as when there are
other errors thrown during the uninstall, Maven itself does not break.
We can as well report this to JAnsi too such that this gets fixed there as well.
What are your opinions on that?
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