Fix Maven plugin help task (#3036)

Fixes #3035

3 files changed, 85 insertions, 39 deletions

diff --git a/runners/maven-plugin/api/maven-plugin.api b/runners/maven-plugin/api/maven-plugin.api
index 28d96bd3..069e7744 100644
--- a/runners/maven-plugin/api/maven-plugin.api
+++ b/runners/maven-plugin/api/maven-plugin.api
@@ -94,6 +94,11 @@ public final class org/jetbrains/dokka/maven/ExternalDocumentationLinkBuilder {
 	public final fun setUrl (Ljava/net/URL;)V
 }
 
+public class org/jetbrains/dokka/maven/HelpMojo : org/apache/maven/plugin/AbstractMojo {
+	public fun <init> ()V
+	public fun execute ()V
+}
+
 public final class org/jetbrains/dokka/maven/MavenDokkaLogger : org/jetbrains/dokka/utilities/DokkaLogger {
 	public fun <init> (Lorg/apache/maven/plugin/logging/Log;)V
 	public fun debug (Ljava/lang/String;)V
diff --git a/runners/maven-plugin/build.gradle.kts b/runners/maven-plugin/build.gradle.kts
index 5e279298..825493ad 100644
--- a/runners/maven-plugin/build.gradle.kts
+++ b/runners/maven-plugin/build.gradle.kts
@@ -2,7 +2,6 @@
  * Copyright 2014-2023 JetBrains s.r.o. Use of this source code is governed by the Apache 2.0 license.
  */
 
-import org.gradle.kotlin.dsl.support.appendReproducibleNewLine
 import org.jetbrains.registerDokkaArtifactPublication
 
 plugins {
@@ -47,77 +46,93 @@ val generatePom by tasks.registering(Sync::class) {
     into(temporaryDir)
 }
 
-val prepareMavenPluginBuildDir by tasks.registering(Sync::class) {
-    description = "Prepares all files for Maven Plugin task execution"
+val prepareHelpMojoDir by tasks.registering(Sync::class) {
+    description = "Prepare files for generating the Maven Plugin HelpMojo"
     group = mavenPluginTaskGroup
 
-    from(tasks.compileKotlin.flatMap { it.destinationDirectory }) { into("classes/java/main") }
-    from(tasks.compileJava.flatMap { it.destinationDirectory }) { into("classes/java/main") }
-
+    into(layout.buildDirectory.dir("maven-help-mojo"))
     from(generatePom)
-
-    into(mavenCliSetup.mavenBuildDir)
 }
 
 val helpMojo by tasks.registering(Exec::class) {
+    description = "Generate the Maven Plugin HelpMojo"
     group = mavenPluginTaskGroup
 
-    dependsOn(tasks.installMavenBinary, prepareMavenPluginBuildDir)
+    dependsOn(tasks.installMavenBinary, prepareHelpMojoDir)
 
-    workingDir(mavenCliSetup.mavenBuildDir)
+    workingDir(prepareHelpMojoDir.map { it.destinationDir })
     executable(mavenCliSetup.mvn.get())
     args("-e", "-B", "org.apache.maven.plugins:maven-plugin-plugin:helpmojo")
 
-    outputs.dir(mavenCliSetup.mavenBuildDir)
-
-    doLast("normalize maven-plugin-help.properties") {
-        // The maven-plugin-help.properties file contains a timestamp by default.
-        // It should be removed as it is not reproducible and impacts Gradle caching
-        val pluginHelpProperties = workingDir.resolve("maven-plugin-help.properties")
-        pluginHelpProperties.writeText(
-            buildString {
-                val lines = pluginHelpProperties.readText().lines().iterator()
-                // the first line is a descriptive comment
-                appendReproducibleNewLine(lines.next())
-                // the second line is the timestamp, which should be ignored
-                lines.next()
-                // the remaining lines are properties
-                lines.forEach { appendReproducibleNewLine(it) }
-            }
-        )
+    outputs.dir(workingDir)
+}
+
+val helpMojoSources by tasks.registering(Sync::class) {
+    description = "Sync the HelpMojo source files into a SourceSet SrcDir"
+    group = mavenPluginTaskGroup
+    from(helpMojo) {
+        eachFile {
+            // drop 2 leading directories
+            relativePath = RelativePath(true, *relativePath.segments.drop(2).toTypedArray())
+        }
     }
+    includeEmptyDirs = false
+    into(temporaryDir)
+    include("**/*.java")
+}
+
+val helpMojoResources by tasks.registering(Sync::class) {
+    description = "Sync the HelpMojo resource files into a SourceSet SrcDir"
+    group = mavenPluginTaskGroup
+    from(helpMojo)
+    into(temporaryDir)
+    include("**/**")
+    exclude("**/*.java")
+}
+
+sourceSets.main {
+    // use the generated HelpMojo as compilation input, so Gradle will automatically generate the mojo
+    java.srcDirs(helpMojoSources)
+    resources.srcDirs(helpMojoResources)
+}
+
+val preparePluginDescriptorDir by tasks.registering(Sync::class) {
+    description = "Prepare files for generating the Maven Plugin descriptor"
+    group = mavenPluginTaskGroup
+
+    into(layout.buildDirectory.dir("maven-plugin-descriptor"))
+
+    from(tasks.compileKotlin) { into("classes/java/main") }
+    from(tasks.compileJava) { into("classes/java/main") }
+    from(helpMojoResources)
 }
 
 val pluginDescriptor by tasks.registering(Exec::class) {
+    description = "Generate the Maven Plugin descriptor"
     group = mavenPluginTaskGroup
 
-    dependsOn(tasks.installMavenBinary, prepareMavenPluginBuildDir)
+    dependsOn(tasks.installMavenBinary, preparePluginDescriptorDir)
 
-    workingDir(mavenCliSetup.mavenBuildDir)
+    workingDir(preparePluginDescriptorDir.map { it.destinationDir })
     executable(mavenCliSetup.mvn.get())
-    args(
-        "-e",
-        "-B",
-        "org.apache.maven.plugins:maven-plugin-plugin:descriptor"
-    )
+    args("-e", "-B", "org.apache.maven.plugins:maven-plugin-plugin:descriptor")
 
-    outputs.dir(layout.buildDirectory.dir("maven/classes/java/main/META-INF/maven"))
+    outputs.dir("$workingDir/classes/java/main/META-INF/maven")
 }
 
 tasks.jar {
-    dependsOn(pluginDescriptor, helpMojo)
     metaInf {
-        from(mavenCliSetup.mavenBuildDir.map { it.dir("classes/java/main/META-INF") })
+        from(pluginDescriptor) {
+            into("maven")
+        }
     }
     manifest {
         attributes("Class-Path" to configurations.runtimeClasspath.map { configuration ->
             configuration.resolve().joinToString(" ") { it.name }
         })
     }
-    duplicatesStrategy = DuplicatesStrategy.WARN
 }
 
-
 registerDokkaArtifactPublication("dokkaMavenPlugin") {
     artifactId = "dokka-maven-plugin"
 }
diff --git a/runners/maven-plugin/pom.template.xml b/runners/maven-plugin/pom.template.xml
index 01ad60d2..b4795112 100644
--- a/runners/maven-plugin/pom.template.xml
+++ b/runners/maven-plugin/pom.template.xml
@@ -12,6 +12,7 @@
     <packaging>maven-plugin</packaging>
     <properties>
         <maven.version>${mavenVersion}</maven.version>
+        <project.build.sourceEncoding>UTF-8</project.build.sourceEncoding>
     </properties>
     <build>
         <plugins>
@@ -21,10 +22,35 @@
                 <version>${mavenPluginToolsVersion}</version>
                 <configuration>
                     <helpPackageName>org.jetbrains.dokka.maven</helpPackageName>
+                    <skipErrorNoDescriptorsFound>true</skipErrorNoDescriptorsFound>
                 </configuration>
+                <executions>
+                    <execution>
+                        <id>default-descriptor</id>
+                        <goals>
+                            <goal>descriptor</goal>
+                        </goals>
+                        <phase>process-classes</phase>
+                    </execution>
+                    <execution>
+                        <id>help-descriptor</id>
+                        <goals>
+                            <goal>helpmojo</goal>
+                        </goals>
+                        <phase>process-classes</phase>
+                    </execution>
+                </executions>
             </plugin>
         </plugins>
         <directory>./</directory>
         <outputDirectory>./classes/java/main</outputDirectory>
     </build>
+    <dependencies>
+        <dependency>
+            <groupId>org.apache.maven.plugin-tools</groupId>
+            <artifactId>maven-plugin-annotations</artifactId>
+            <version>${mavenPluginToolsVersion}</version>
+            <scope>provided</scope>
+        </dependency>
+    </dependencies>
 </project>