Include sources from composite builds in Groovydoc

Updated the Groovydoc configuration to collect source directories from included (composite) builds by inspecting the file system. This ensures documentation generation includes sources from all relevant projects, and adds exclusions to prevent duplicate class errors.

Author: jamesfredley

grails-doc/build.gradle

@@ -82,13 +82,36 @@ combinedGroovydoc.configure { Groovydoc gdoc ->
                 possibleSources
             }
             .flatten()
-    gdoc.source(sources.collect { SourceSet it -> [it.allSource.srcDirs, it.allSource.srcDirs] }.flatten().findAll { File srcDir ->
-        if (!(srcDir.name in ['java', 'groovy'])) {
-            return false
-        }
 
-        srcDir.exists()
-    }.unique())
+    List<File> baseSourceDirs = sources
+            .collect { SourceSet it -> it.allSource.srcDirs }
+            .flatten()
+            .findAll { File srcDir ->
+                if (!(srcDir.name in ['java', 'groovy'])) {
+                    return false
+                }
+                srcDir.exists()
+            }
+
+    // Collect source directories from included builds (composite builds)
+    // Gradle will not provide the included build projects or source sets, so we inspect the file system
+    List<File> includedBuildSourceDirs = gradle.includedBuilds
+            .collectMany { includedBuild ->
+                def sourceDirs = []
+                includedBuild.projectDir.eachDirRecurse { File dir ->
+                    ['src/main/java', 'src/main/groovy'].each { rel ->
+                        File sourceDir = new File(dir, rel)
+                        if (sourceDir.isDirectory()) {
+                            sourceDirs << sourceDir
+                        }
+                    }
+                }
+                sourceDirs
+            }
+
+    gdoc.source(project.files((baseSourceDirs + includedBuildSourceDirs).unique()))
+    // Exclude files that are not part of the public API and cause duplicate class errors when combined with other source sets
+    gdoc.exclude('org/grails/example/**', 'org.grails.example/**', 'another/**', 'TestJava**')
 
     gdoc.classpath = files(sources.collect { SourceSet it -> it.compileClasspath.filter(File.&isDirectory) }.flatten().unique())
     gdoc.destinationDir = project.layout.buildDirectory.dir('combined-api/api').get().asFile