gnodet opened a new pull request, #13658:
URL: https://github.com/apache/maven/pull/13658
## Summary
Implements a JSR 269 annotation processor (`maven-api-plugin-processor`)
that generates Maven plugin descriptors (`META-INF/maven/plugin.xml`) and DI
factory classes at **compile time** from `@Mojo`-annotated classes, eliminating
the need for the external `maven-plugin-plugin` (from maven-plugin-tools) for
Maven 4 plugins.
Closes #13644
## Design
Follows the `maven-api-di` / `DiIndexProcessor` pattern:
- **Zero external dependencies** — only `java.compiler` + `java.xml` JDK
modules
- Self-processing disabled via
`<maven.compiler.proc>none</maven.compiler.proc>`
- Service registration via both
`META-INF/services/javax.annotation.processing.Processor` and
`module-info.java` `provides` clause
- Returns `false` from `process()` — does not claim `@Mojo`; other
processors and IDEs can still see it
- Annotation references are **string-based** — no compile dependency on
`maven-api-core` or `maven-api-di`
## What gets generated
### 1. `META-INF/maven/plugin.xml` (v2.0.0 namespace)
Extracts:
- `@Mojo` attributes (goal name, defaultPhase, projectRequired, aggregator,
onlineRequired, configurator, dependencyCollection,
dependencyResolutionPathScopes)
- `@Execute` (phase, goal, lifecycle)
- `@After` / `@Afters` (repeatable) → `<afterLinks>`
- `@Parameter` on fields/methods — walks full type hierarchy via
`TypeElement.getSuperclass()`
- `@Resolution` on fields — same hierarchy walk
- Javadoc via `Elements.getDocComment()` — description (with inline tag
stripping), `@since`, `@deprecated`
### 2. Factory source file per mojo
For `com.example.MyMojo` with `@Mojo(name = "goal")`:
```java
@org.apache.maven.api.di.Named("groupId:artifactId:version:goal")
public class MyMojo$MojoFactory extends MyMojo {}
```
The `DiIndexProcessor` (from `maven-api-di`) picks up the `@Named` factory
in the next round and adds it to
`META-INF/maven/org.apache.maven.api.di.Inject` automatically. This factory is
required because `DefaultMavenPluginManager.loadV4Mojo()` looks up mojos via
`Key.of(implementationClass, roleHint)` where `roleHint =
"groupId:artifactId:version:goal"`.
## Required compiler options (via `-A`)
| Option | Required | Description |
|--------|----------|-------------|
| `maven.plugin.groupId` | yes | Plugin group ID |
| `maven.plugin.artifactId` | yes | Plugin artifact ID |
| `maven.plugin.version` | yes | Plugin version |
| `maven.plugin.goalPrefix` | no | Derived from artifactId if absent |
## Files
- `api/maven-api-plugin-processor/pom.xml` — module POM (parent:
`maven-api`, no deps, proc=none)
- `api/maven-api-plugin-processor/src/main/java/module-info.java` — exports
package, requires `java.compiler` + `java.xml`, provides `Processor`
-
`api/maven-api-plugin-processor/src/main/java/org/apache/maven/plugin/processor/MojoDescriptorProcessor.java`
— the processor
-
`api/maven-api-plugin-processor/src/main/resources/META-INF/services/javax.annotation.processing.Processor`
— service registration
- `api/pom.xml` — adds `maven-api-plugin-processor` module (after
`maven-api-core`)
## Verification
Manually tested against the `mng-12534` IT `TouchMojo` — generated output:
```xml
<?xml version="1.0" encoding="UTF-8"?>
<plugin xmlns="http://maven.apache.org/PLUGIN/2.0.0";>
<name>mng12534-plugin</name>
<groupId>org.apache.maven.its.mng12534</groupId>
<artifactId>mng12534-plugin</artifactId>
<version>1.0-SNAPSHOT</version>
<goalPrefix>mng12534</goalPrefix>
<mojos>
<mojo>
<goal>touch</goal>
<phase>compile</phase>
<implementation>org.apache.maven.its.mng12534.TouchMojo</implementation>
<language>java</language>
<description>...</description>
<projectRequired>true</projectRequired>
<onlineRequired>false</onlineRequired>
<aggregator>false</aggregator>
<afterLinks>
<afterLink>
<phase>resources</phase>
<type>PROJECT</type>
</afterLink>
</afterLinks>
</mojo>
</mojos>
</plugin>
```
## Next steps (not in this PR)
- Unit test using `javax.tools.JavaCompiler` API
- Update `mng-12534-after-annotation` IT to use the processor instead of
handcrafted `plugin.xml` + factory
- Update issue #13644 (factory classes ARE needed for DI lookup)
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