Add support for generating javadoc with Dackka

PiperOrigin-RevId: 396297834

javadoc_combined.gradle

@@ -16,22 +16,27 @@ apply from: "${buildscript.sourceFile.parentFile}/javadoc_util.gradle"
 
 class CombinedJavadocPlugin implements Plugin<Project> {
 
-  static final String TASK_NAME = "generateCombinedJavadoc"
+  static final String JAVADOC_TASK_NAME = "generateCombinedJavadoc"
+  static final String DACKKA_TASK_NAME = "generateCombinedDackka"
+
+  static final String DACKKA_JAR_URL =
+      "https://androidx.dev/dackka/builds/7709825/artifacts/dackka-0.0.9.jar"
 
   @Override
   void apply(Project project) {
     project.gradle.projectsEvaluated {
       Set<Project> libraryModules = getLibraryModules(project)
       if (!libraryModules.isEmpty()) {
-        project.task(TASK_NAME, type: Javadoc) {
+        def guavaReferenceUrl = "https://guava.dev/releases/$project.ext.guavaVersion/api/docs"
+
+        project.task(JAVADOC_TASK_NAME, type: Javadoc) {
           description = "Generates combined Javadoc."
           title = "ExoPlayer library"
           source = libraryModules.generateJavadoc.source
           classpath = project.files([])
           destinationDir = project.file("$project.buildDir/docs/javadoc")
           options {
-            links "https://developer.android.com/reference",
+            links "https://developer.android.com/reference", guavaReferenceUrl
-                  "https://guava.dev/releases/$project.ext.guavaVersion/api/docs"
             encoding = "UTF-8"
           }
           options.addBooleanOption "-no-module-directories", true
@@ -60,6 +65,54 @@ class CombinedJavadocPlugin implements Plugin<Project> {
             project.fixJavadoc()
           }
         }
+
+        project.task(DACKKA_TASK_NAME, type: JavaExec) {
+          doFirst {
+            // Recreate the output directory to remove any leftover files from a previous run.
+            def outputDir = project.file("$project.buildDir/docs/dackka")
+            project.delete outputDir
+            project.mkdir outputDir
+
+            // Download the Dackka JAR.
+            new URL(DACKKA_JAR_URL).withInputStream {
+              i -> classpath.getSingleFile().withOutputStream { it << i }
+            }
+
+            // Build lists of source files and dependencies.
+            def sources = []
+            def dependencies = []
+            libraryModules.each { libraryModule ->
+              libraryModule.android.libraryVariants.all { variant ->
+                def name = variant.buildType.name
+                if (name == "release") {
+                  def classpathFiles =
+                      project.files(variant.javaCompileProvider.get().classpath.files)
+                  variant.sourceSets.inject(sources) {
+                    acc, val -> acc << val.javaDirectories
+                  }
+                  dependencies << classpathFiles.filter { f -> !(f.path.contains("/buildout/")) }
+                  dependencies << libraryModule.project.android.getBootClasspath()
+                }
+              }
+            }
+
+            // Set command line arguments to Dackka.
+            def guavaPackageListFile = getGuavaPackageListFile(getTemporaryDir())
+            def globalLinksString = "$guavaReferenceUrl^$guavaPackageListFile^^"
+            def sourcesString = project.files(sources.flatten())
+                .filter({ f -> project.file(f).exists() }).join(";")
+            def dependenciesString = project.files(dependencies).asPath.replace(':', ';')
+            args("-moduleName", "",
+                "-outputDir", "$outputDir",
+                "-globalLinks", "$globalLinksString",
+                "-loggingLevel", "WARN",
+                "-sourceSet", "-src $sourcesString -classpath $dependenciesString",
+                "-offlineMode")
+            environment("DEVSITE_TENANT", "androidx")
+          }
+          description = "Generates combined javadoc for developer.android.com."
+          classpath = project.files(new File(getTemporaryDir(), "dackka.jar"))
+        }
       }
     }
   }
@@ -72,6 +125,17 @@ class CombinedJavadocPlugin implements Plugin<Project> {
     }
   }
 
+  // Returns a file containing the list of packages that should be linked to Guava documentation.
+  private static File getGuavaPackageListFile(File directory) {
+    def packageListFile = new File(directory, "guava")
+    packageListFile.text = ["com.google.common.base", "com.google.common.collect",
+                            "com.google.common.io", "com.google.common.math",
+                            "com.google.common.net", "com.google.common.primitives",
+                            "com.google.common.truth", "com.google.common.util.concurrent"]
+        .join('\n')
+    return packageListFile
+  }
+
 }
 
 apply plugin: CombinedJavadocPlugin