Add module detector settings plugin

build-logic/module-detector/build.gradle.kts

@@ -0,0 +1,16 @@
+plugins {
+    `kotlin-dsl`
+}
+
+dependencies {
+    testImplementation(libs.test.junit)
+}
+
+gradlePlugin {
+    plugins {
+        register("moduleDetector") {
+            id = "moop.module.detector"
+            implementationClass = "ModuleDetectorPlugin"
+        }
+    }
+}

build-logic/module-detector/src/main/kotlin/ModuleDetectorPlugin.kt

@@ -0,0 +1,31 @@
+import org.gradle.api.Plugin
+import org.gradle.api.initialization.Settings
+import java.io.File
+
+/**
+ * Includes every directory that has a build.gradle(.kts) file as a module,
+ * so settings.gradle.kts needs no include list.
+ */
+class ModuleDetectorPlugin : Plugin<Settings> {
+    override fun apply(settings: Settings) {
+        settings.include(findModules(settings.rootDir))
+    }
+}
+
+/**
+ * Returns the sorted Gradle paths of the modules below [rootDir].
+ * Hidden and build directories are skipped, and so are nested builds with their own settings file.
+ */
+internal fun findModules(rootDir: File): List<String> =
+    rootDir.subDirs().flatMap { it.modules(":${it.name}") }.sorted()
+
+private fun File.modules(path: String): List<String> = when {
+    hasFile("settings.gradle", "settings.gradle.kts") -> emptyList()
+    hasFile("build.gradle", "build.gradle.kts") -> listOf(path)
+    else -> subDirs().flatMap { it.modules("$path:${it.name}") }
+}
+
+private fun File.hasFile(vararg names: String): Boolean = names.any { resolve(it).isFile }
+
+private fun File.subDirs(): List<File> =
+    listFiles().orEmpty().filter { !it.name.startsWith(".") && it.name != "build" && it.isDirectory }

build-logic/module-detector/src/test/kotlin/ModuleDetectorPluginTest.kt

@@ -0,0 +1,45 @@
+import org.junit.Assert.assertEquals
+import org.junit.Rule
+import org.junit.Test
+import org.junit.rules.TemporaryFolder
+
+class ModuleDetectorPluginTest {
+
+    @get:Rule
+    val tempFolder = TemporaryFolder()
+
+    @Test
+    fun findModules_includesDirectoriesWithBuildFile() {
+        createFile("build.gradle.kts")
+        createFile("app/build.gradle")
+        createFile("feature/home/api/build.gradle.kts")
+        createFile("feature/home/impl/build.gradle")
+        createFile("feature/home/impl/src/build.gradle")
+        tempFolder.newFolder("docs")
+
+        assertEquals(listOf(":app", ":feature:home:api", ":feature:home:impl"), findModules(tempFolder.root))
+    }
+
+    @Test
+    fun findModules_skipsHiddenAndBuildDirectories() {
+        createFile(".gradle/cache/build.gradle")
+        createFile("build/generated/build.gradle")
+        createFile("feature/build/tmp/build.gradle")
+        createFile("app/build.gradle")
+
+        assertEquals(listOf(":app"), findModules(tempFolder.root))
+    }
+
+    @Test
+    fun findModules_skipsNestedBuilds() {
+        createFile("build-logic/settings.gradle.kts")
+        createFile("build-logic/convention/build.gradle.kts")
+        createFile("app/build.gradle")
+
+        assertEquals(listOf(":app"), findModules(tempFolder.root))
+    }
+
+    private fun createFile(path: String) {
+        tempFolder.root.resolve(path).apply { parentFile.mkdirs() }.createNewFile()
+    }
+}

build-logic/settings.gradle.kts

@@ -11,3 +11,4 @@ dependencyResolutionManagement {
 }
 
 include(":convention")
+include(":module-detector")

settings.gradle.kts

@@ -7,6 +7,11 @@ pluginManagement {
     }
 }
 
+plugins {
+    // Automatically includes every directory that has a build.gradle(.kts) file.
+    id("moop.module.detector")
+}
+
 dependencyResolutionManagement {
     repositoriesMode.set(RepositoriesMode.FAIL_ON_PROJECT_REPOS)
     repositories {
@@ -23,55 +28,3 @@ dependencyResolutionManagement {
 }
 
 enableFeaturePreview("TYPESAFE_PROJECT_ACCESSORS")
-
-// Automatically detect modules.
-ModuleDetector.modules(rootDir).forEach { module ->
-    include(module)
-}
-
-private object ModuleDetector {
-
-    fun modules(rootDir: File) : List<String> {
-        return rootDir.listDirs().flatMap { dir ->
-            findModules(parent = "", dir = dir)
-        }
-    }
-
-    private fun findModules(parent: String, dir: File): List<String> {
-        if (dir.isDirectory.not() || dir.isProject()) {
-            return emptyList()
-        }
-
-        val current: String = parent + ":" + dir.name
-        return if (dir.isModule()) {
-            println("include '$current'")
-            listOf(current)
-        } else {
-            dir.listDirs().flatMap { subDir ->
-                findModules(parent = current, dir = subDir)
-            }
-        }
-    }
-
-    private fun File.isProject(): Boolean {
-        if (isDirectory.not()) {
-            return false
-        }
-        return listFiles().orEmpty().any {
-            it.isFile && (it.name == "settings.gradle" || it.name == "settings.gradle.kts")
-        }
-    }
-
-    private fun File.isModule(): Boolean {
-        if (isDirectory.not()) {
-            return false
-        }
-        return listFiles().orEmpty().any {
-            it.isFile && (it.name == "build.gradle" || it.name == "build.gradle.kts")
-        }
-    }
-
-    private fun File.listDirs(): List<File> {
-        return listFiles().orEmpty().filter { it.isDirectory }
-    }
-}