NPE in daemon prompter when using iteractive mode with no project (using archetype)

[rmannibucau]

Here is the stack

$ mvn archetype:generate -DarchetypeGroupId=org.apache.maven.archetypes -DarchetypeArtifactId=maven-archetype-quickstart -DarchetypeVersion=1.4 -e
[INFO] Error stacktraces are turned on.
[INFO] Scanning for projects...
[INFO] BuildTimeEventSpy is registered.
[INFO] 
[INFO] -------------------------------------------< org.apache.maven:standalone-pom >--------------------------------------------
[INFO] Building Maven Stub Project (No POM) 1
[INFO] ---------------------------------------------------------[ pom ]----------------------------------------------------------
[INFO] 
[INFO] --- archetype:3.2.0:generate (default-cli) @ standalone-pom ---
[INFO] Generating project in Interactive mode
[INFO] Archetype repository not defined. Using the one from [org.apache.maven.archetypes:maven-archetype-quickstart:1.4] found in catalog remote
[INFO] --------------------------------------------------------------------------------------------------------------------------
[INFO] BUILD FAILURE
[INFO] --------------------------------------------------------------------------------------------------------------------------
[INFO] Total time:  1.860 s
[INFO] Finished at: 2023-03-10T10:00:51+01:00
[INFO] --------------------------------------------------------------------------------------------------------------------------
[ERROR] Failed to execute goal org.apache.maven.plugins:maven-archetype-plugin:3.2.0:generate (default-cli) on project standalone-pom: Failed to prompt user: Unable to prompt user: NullPointerException -> [Help 1]

org.apache.maven.lifecycle.LifecycleExecutionException: Failed to execute goal org.apache.maven.plugins:maven-archetype-plugin:3.2.0:generate (default-cli) on project standalone-pom: Failed to prompt user
	at org.apache.maven.lifecycle.internal.MojoExecutor.doExecute2(MojoExecutor.java:341)
	at org.apache.maven.lifecycle.internal.MojoExecutor.doExecute(MojoExecutor.java:324)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:212)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:174)
	at org.apache.maven.lifecycle.internal.MojoExecutor.access$000(MojoExecutor.java:77)
	at org.apache.maven.lifecycle.internal.MojoExecutor$1.run(MojoExecutor.java:162)
	at org.apache.maven.plugin.DefaultMojosExecutionStrategy.execute(DefaultMojosExecutionStrategy.java:39)
	at org.apache.maven.lifecycle.internal.MojoExecutor.execute(MojoExecutor.java:159)
	at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:114)
	at org.apache.maven.lifecycle.internal.LifecycleModuleBuilder.buildProject(LifecycleModuleBuilder.java:80)
	at org.apache.maven.lifecycle.internal.builder.singlethreaded.SingleThreadedBuilder.build(SingleThreadedBuilder.java:60)
	at org.apache.maven.lifecycle.internal.LifecycleStarter.execute(LifecycleStarter.java:132)
	at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:313)
	at org.apache.maven.DefaultMaven.doExecute(DefaultMaven.java:228)
	at org.apache.maven.DefaultMaven.execute(DefaultMaven.java:153)
	at org.apache.maven.cli.MavenCli.execute(MavenCli.java:859)
	at org.apache.maven.cli.MavenCli.doMain(MavenCli.java:282)
	at org.apache.maven.cli.MavenCli.main(MavenCli.java:198)
...
Caused by: java.io.IOException: Unable to prompt user
	at org.mvndaemon.mvnd.interactivity.DaemonPrompter.doPrompt(DaemonPrompter.java:175)
	at org.mvndaemon.mvnd.interactivity.DaemonPrompter.doPrompt(DaemonPrompter.java:111)
	... 32 common frames omitted
Caused by: java.lang.NullPointerException: null
	at java.base/java.util.Objects.requireNonNull(Objects.java:221)
	at org.mvndaemon.mvnd.interactivity.DaemonPrompter.doPrompt(DaemonPrompter.java:166)
	... 33 common frames omitted

[psiroky]

Which version of mvnd are you seeing this with? I tried with 0.9.0 and the latest master (ca4bdd0), but could not reproduce.

That being said, DaemonPrompter.java:166 contains Connection con = Objects.requireNonNull(Connection.getCurrent()); which seems like the the connection got lost for some reason? But then I am not sure how would the error message / stacktrace got to the client.

[gnodet]

Which version of mvnd are you seeing this with? I tried with 0.9.0 and the latest master (ca4bdd0), but could not reproduce.

That being said, DaemonPrompter.java:166 contains Connection con = Objects.requireNonNull(Connection.getCurrent()); which seems like the the connection got lost for some reason? But then I am not sure how would the error message / stacktrace got to the client.

I think that's using the mvn script from mvnd, that's why there's no connection...
But the DaemonPrompter is used anyway, so I think, if there's no connection, it should delegate to the usual one (or duplicate the behaviour and go to the console). An alternative would be to split the classpath so that when launching maven, the class loader would not contain any maven daemon specific classes.
It should be easier, now that all processes are using the plexus class world's launcher to boot.

[rmannibucau]

Think the option to have a mvn.m2.conf and a mvnd.m2.conf is very tempting.

[gnodet]

Think the option to have a mvn.m2.conf and a mvnd.m2.conf is very tempting.

We already have 3 configs in the master: one for maven, one for the mvnd client and one for the mvnd daemon. So it's just a matter of modifying the distribution / config so that the daemon jars are not included when starting maven.