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Generated factory for a Maven 4 API mojo requires a no-arg constructor

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Since Oct 6, 2026.

  • #1236 by @CaptainAni187 — open

Assessment

Difficulty
3/5
Estimated time
1-2 days
Newbie friendliness
68/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
java
Domain
build-system, tooling

Research direction

Start in DescriptorGeneratorMojo.java around line 530, following the descriptor goal's generated Factory constructor. Use the supplied constructor-injected ReproMojo to reproduce the runtime failure with Maven 4. Done means the generated factory handles the mojo's @Inject constructor, or descriptor rejects a mojo without a no-arg constructor instead of producing a failing plugin.

Written by the indexing model from the issue text.

Description

bug
Affected version

4.0.0-beta-3; the code is unchanged on master

Bug description

For each Maven 4 API mojo, the descriptor goal generates a <Mojo>Factory subclass whose only constructor calls the mojo's no-arg constructor (DescriptorGeneratorMojo.java:530). A mojo that uses constructor injection and has no no-arg constructor builds cleanly, then fails when the goal runs:

Caused by: org.apache.maven.di.impl.DIException: Failed to call constructor public repro.ReproMojoFactory() to provide requested key @Named("repro:ctor-maven-plugin:1.0-SNAPSHOT:run") ReproMojoFactory
Caused by: java.lang.NoSuchMethodError: repro.ReproMojo: method 'void <init>()' not found

Reproducer, built with maven-plugin-plugin 4.0.0-beta-3 and run with Maven 4.0.0-rc-7:

@Mojo(name = "run")
public class ReproMojo implements org.apache.maven.api.plugin.Mojo {
    private final Log log;

    @Inject
    public ReproMojo(Log log) {
        this.log = log;
    }

    public void execute() {
        log.info("constructor-injected mojo ran");
    }
}

Expected: the factory mirrors the mojo's @Inject constructor and passes its parameters to super(...). Failing that, descriptor should reject a mojo without a no-arg constructor instead of producing a plugin that fails at run time.

The Maven 4 API ports in apache/maven#13302 had to switch mojos from constructor to field injection because of this.

Dominant language
Java
Stars
63
Forks
76
Avg merge
20h 52m
Merged PRs (30d)
21

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