Remove AGP-internal imports from VersionFetcher and migrate compileSdk/ndk reads to the public DSL

packages/flutter_tools/gradle/src/main/kotlin/AgpCommonExtensionWrapper.kt

@@ -40,6 +40,25 @@ class AgpCommonExtensionWrapper(
             }
         }
 
+    var compileSdkPreview: String?
+        get() =
+            when (backingExtension) {
+                is ApplicationExtension -> backingExtension.compileSdkPreview
+                is LibraryExtension -> backingExtension.compileSdkPreview
+                is DynamicFeatureExtension -> backingExtension.compileSdkPreview
+                is TestExtension -> backingExtension.compileSdkPreview
+                else -> throw IllegalArgumentException(unsupportedMessage())
+            }
+        set(value) {
+            when (backingExtension) {
+                is ApplicationExtension -> backingExtension.compileSdkPreview = value
+                is LibraryExtension -> backingExtension.compileSdkPreview = value
+                is DynamicFeatureExtension -> backingExtension.compileSdkPreview = value
+                is TestExtension -> backingExtension.compileSdkPreview = value
+                else -> throw IllegalArgumentException(unsupportedMessage())
+            }
+        }
+
     var namespace: String?
         get() =
             when (backingExtension) {

packages/flutter_tools/gradle/src/main/kotlin/FlutterPluginUtils.kt

@@ -528,18 +528,21 @@ object FlutterPluginUtils {
     internal fun getAndroidApplicationExtension(project: Project): ApplicationExtension =
         project.extensions.getByType(ApplicationExtension::class.java)
 
-    internal fun getConfiguredNdkVersion(project: Project): String? =
-        project.extensions.findByType(ApplicationExtension::class.java)?.ndkVersion
-            ?: getLegacyAndroidExtension(project).ndkVersion
+    internal fun getConfiguredNdkVersion(project: Project): String? = getAndroidExtension(project).ndkVersion
 
     /**
-     * Expected format of getAndroidExtension(project).compileSdkVersion is a string of the form
-     * `android-` followed by either the numeric version, e.g. `android-35`, or a preview version,
-     * e.g. `android-UpsideDownCake`.
+     * Returns the compile SDK configured on the project's Android extension: the numeric
+     * API level (`compileSdk = 36`) or a preview codename (`compileSdkPreview = "Baklava"`).
      */
     @JvmStatic
     @JvmName("getCompileSdkFromProject")
-    internal fun getCompileSdkFromProject(project: Project): String = getLegacyAndroidExtension(project).compileSdkVersion!!.substring(8)
+    internal fun getCompileSdkFromProject(project: Project): CompileSdkVersion {
+        val androidExtension = getAndroidExtension(project)
+        return CompileSdkVersion(
+            apiLevel = androidExtension.compileSdk,
+            previewCodename = androidExtension.compileSdkPreview
+        )
+    }
 
     /**
      * Returns:

packages/flutter_tools/gradle/src/main/kotlin/VersionFetcher.kt

@@ -6,7 +6,6 @@ package com.flutter.gradle
 
 import com.android.build.api.AndroidPluginVersion
 import com.android.build.api.variant.AndroidComponentsExtension
-import com.android.build.gradle.internal.utils.getKotlinAndroidPluginVersion
 import org.gradle.api.JavaVersion
 import org.gradle.api.Project
 import org.jetbrains.kotlin.gradle.plugin.KotlinAndroidPluginWrapper
@@ -42,19 +41,16 @@ internal object VersionFetcher {
     }
 
     /**
-     * Returns the version of the Kotlin Gradle plugin.
+     * Returns the version of the Kotlin Gradle plugin, or null if it cannot be determined.
+     *
+     * Null is an expected result when the Kotlin Gradle plugin has not been applied to the
+     * project — most notably under AGP's built-in Kotlin support (`android.builtInKotlin`),
+     * where there is no standalone KGP. Callers must treat null as "unknown/not applied",
+     * not as an error.
      */
     internal fun getKGPVersion(project: Project): Version? {
-        // AGP and Kgp have methods for getting kotlin version.
-        // AGP's method is internal, we try to use it anyway.
         // KGP's version in org.jetbrains.kotlin.gradle.plugin.DefaultKotlinBasePlugin is not
         // available when this method is called.
-        // When testing call `setAgpKotlinVersionToNull(project)`.
-        val agpDefinedKgpVersion = getKotlinAndroidPluginVersion(project)
-        if (agpDefinedKgpVersion != null && agpDefinedKgpVersion != "unknown") {
-            return Version.fromString(agpDefinedKgpVersion)
-        }
-
         val kotlinVersionProperty = "kotlin_version"
         val firstKotlinVersionFieldName = "pluginVersion"
         val secondKotlinVersionFieldName = "kotlinPluginVersion"
@@ -127,3 +123,35 @@ internal class Version(
 
     override fun toString(): String = "$major.$minor.$patch"
 }
+
+/**
+ * The compile SDK configured on a project's Android extension: either a numeric API level
+ * (`compileSdk = 36`) or a preview codename (`compileSdkPreview = "Baklava"`). Both are null
+ * when the DSL has not been configured (yet).
+ */
+internal data class CompileSdkVersion(
+    val apiLevel: Int?,
+    val previewCodename: String?
+) {
+    /**
+     * Whether this compile SDK is known to be higher than [other].
+     *
+     * - numeric vs numeric: numeric comparison.
+     * - preview vs numeric: a preview codename targets an unreleased SDK, so it is
+     *   considered higher than any numeric API level.
+     * - preview vs preview: codenames stopped being alphabetically ordered when the
+     *   alphabet reset at "Baklava", so distinct codenames are incomparable and this
+     *   returns false rather than guessing.
+     * - if either side is unset, returns false.
+     */
+    fun isHigherThan(other: CompileSdkVersion): Boolean =
+        when {
+            previewCodename != null && other.previewCodename != null -> false
+            previewCodename != null && other.apiLevel != null -> true
+            apiLevel != null && other.apiLevel != null -> apiLevel > other.apiLevel
+            else -> false
+        }
+
+    /** The human-readable form used in log messages, e.g. "35" or "Baklava". */
+    override fun toString(): String = previewCodename ?: apiLevel?.toString() ?: "unknown"
+}

packages/flutter_tools/gradle/src/main/kotlin/plugins/PluginHandler.kt

@@ -5,6 +5,7 @@
 package com.flutter.gradle.plugins
 
 import com.android.builder.model.BuildType
+import com.flutter.gradle.CompileSdkVersion
 import com.flutter.gradle.FlutterExtension
 import com.flutter.gradle.FlutterPluginUtils
 import com.flutter.gradle.FlutterPluginUtils.addApiDependencies
@@ -121,12 +122,9 @@ class PluginHandler(
             // Wait until the Android plugin loaded.
             pluginProject.afterEvaluate {
                 // Checks if there is a mismatch between the plugin compileSdkVersion and the project compileSdkVersion.
-                val projectCompileSdkVersion: String = getCompileSdkFromProject(project)
-                val pluginCompileSdkVersion: String = getCompileSdkFromProject(pluginProject)
-                // TODO(gmackall): This is doing a string comparison, which is odd and also can be wrong
-                //                 when comparing preview versions (against non preview, and also in the
-                //                 case of alphabet reset which happened with "Baklava".
-                if (pluginCompileSdkVersion > projectCompileSdkVersion) {
+                val projectCompileSdkVersion: CompileSdkVersion = getCompileSdkFromProject(project)
+                val pluginCompileSdkVersion: CompileSdkVersion = getCompileSdkFromProject(pluginProject)
+                if (pluginCompileSdkVersion.isHigherThan(projectCompileSdkVersion)) {
                     project.logger.quiet(
                         "Warning: The plugin $pluginName requires Android SDK version $pluginCompileSdkVersion or higher."
                     )

packages/flutter_tools/gradle/src/test/kotlin/DependencyVersionCheckerTest.kt

@@ -30,7 +30,6 @@ import com.flutter.gradle.DependencyVersionChecker.warnAGPVersion
 import com.flutter.gradle.DependencyVersionChecker.warnGradleVersion
 import com.flutter.gradle.DependencyVersionChecker.warnKGPVersion
 import com.flutter.gradle.DependencyVersionChecker.warnMinSdkVersion
-import com.flutter.gradle.testing.setAgpKotlinVersionToNull
 import io.mockk.every
 import io.mockk.mockk
 import io.mockk.mockkStatic
@@ -499,7 +498,6 @@ private object MockProjectFactory {
             }
             return@answers Unit
         }
-        setAgpKotlinVersionToNull(mockProject)
 
         return mockProject
     }

packages/flutter_tools/gradle/src/test/kotlin/FlutterPluginUtilsTest.kt

@@ -616,9 +616,25 @@ class FlutterPluginUtilsTest {
     @Test
     fun `getCompileSdkFromProject returns the compileSdk from the project`() {
         val project = mockk<Project>()
-        every { project.extensions.findByType(BaseExtension::class.java)!!.compileSdkVersion } returns "android-35"
+        val androidExtension = mockk<com.android.build.api.dsl.ApplicationExtension>()
+        every { project.extensions.findByName("android") } returns androidExtension
+        every { androidExtension.compileSdk } returns 35
+        every { androidExtension.compileSdkPreview } returns null
         val result = FlutterPluginUtils.getCompileSdkFromProject(project)
-        assertEquals("35", result)
+        assertEquals(CompileSdkVersion(apiLevel = 35, previewCodename = null), result)
+        assertEquals("35", result.toString())
+    }
+
+    @Test
+    fun `getCompileSdkFromProject returns the preview codename from the project`() {
+        val project = mockk<Project>()
+        val androidExtension = mockk<com.android.build.api.dsl.ApplicationExtension>()
+        every { project.extensions.findByName("android") } returns androidExtension
+        every { androidExtension.compileSdk } returns null
+        every { androidExtension.compileSdkPreview } returns "Baklava"
+        val result = FlutterPluginUtils.getCompileSdkFromProject(project)
+        assertEquals(CompileSdkVersion(apiLevel = null, previewCodename = "Baklava"), result)
+        assertEquals("Baklava", result.toString())
     }
 
     @Test
@@ -1966,7 +1982,9 @@ class FlutterPluginUtilsTest {
         every { project.findProperty(FlutterPluginUtils.PROP_INSTALLED_NDK_VERSIONS) } returns ""
         every { project.gradle.startParameter.taskNames } returns emptyList()
         every { project.gradle.startParameter.isOffline } returns false
-        every { project.extensions.findByType(ApplicationExtension::class.java) } returns null
+        val mockAndroidExtension = mockk<ApplicationExtension>()
+        every { project.extensions.findByName("android") } returns mockAndroidExtension
+        every { mockAndroidExtension.ndkVersion } returns "29.0.13846066"
         every { project.serviceOf<ExecOperations>() } returns mockExecOperations
         every { mockExecOperations.exec(capture(execActionSlot)) } answers {
             File(tempDir.toFile(), "ndk/29.0.13846066/source.properties").apply {
@@ -2016,7 +2034,9 @@ class FlutterPluginUtilsTest {
         every { project.findProperty(FlutterPluginUtils.PROP_ANDROID_SDK_ROOT) } returns "/sdk/root"
         every { project.findProperty(FlutterPluginUtils.PROP_INSTALLED_NDK_VERSIONS) } returns "29.0.13846066"
         every { project.gradle.startParameter.taskNames } returns emptyList()
-        every { project.extensions.findByType(ApplicationExtension::class.java) } returns null
+        val mockAndroidExtension = mockk<ApplicationExtension>()
+        every { project.extensions.findByName("android") } returns mockAndroidExtension
+        every { mockAndroidExtension.ndkVersion } returns "29.0.13846066"
 
         FlutterPluginUtils.forceNdkDownload(project, "/base/path")
         finalizeDslSlot.captured.invoke(Any())
@@ -2104,7 +2124,9 @@ class FlutterPluginUtilsTest {
         } returns "26.3.11579264"
         every { project.gradle.startParameter.taskNames } returns emptyList()
         every { project.gradle.startParameter.isOffline } returns false
-        every { project.extensions.findByType(ApplicationExtension::class.java) } returns null
+        val mockAndroidExtension = mockk<ApplicationExtension>()
+        every { project.extensions.findByName("android") } returns mockAndroidExtension
+        every { mockAndroidExtension.ndkVersion } answers { configuredNdkVersion }
         every { project.serviceOf<ExecOperations>() } returns mockExecOperations
         every { mockExecOperations.exec(capture(execActionSlot)) } answers {
             File(tempDir.toFile(), "ndk/27.3.13750724/source.properties").apply {
@@ -2166,6 +2188,7 @@ class FlutterPluginUtilsTest {
             )
         }
         every { mockApplicationExtension.ndkVersion } answers { configuredNdkVersion }
+        every { project.extensions.findByName("android") } returns mockApplicationExtension
         every { mockCmakeOptions.path } returns null
         every { project.findProperty(FlutterPluginUtils.PROP_SDK_MANAGER_PATH) } returns "/sdkmanager"
         every { project.findProperty(FlutterPluginUtils.PROP_ANDROID_SDK_ROOT) } returns tempDir.toString()
@@ -2225,6 +2248,9 @@ class FlutterPluginUtilsTest {
         every { project.findProperty(FlutterPluginUtils.PROP_ANDROID_SDK_ROOT) } returns "/sdk/root"
         every { project.findProperty(FlutterPluginUtils.PROP_INSTALLED_NDK_VERSIONS) } returns "29.0.13846066"
         every { project.gradle.startParameter.taskNames } returns emptyList()
+        val mockAndroidExtension = mockk<ApplicationExtension>()
+        every { project.extensions.findByName("android") } returns mockAndroidExtension
+        every { mockAndroidExtension.ndkVersion } returns "29.0.13846066"
 
         FlutterPluginUtils.forceNdkDownload(project, "/base/path")
         finalizeDslSlot.captured.invoke(Any())
@@ -2252,6 +2278,7 @@ class FlutterPluginUtilsTest {
             throw AssertionError("legacy ndkVersion should not be read when ApplicationExtension is available")
         }
         every { mockApplicationExtension.ndkVersion } returns "29.0.13846066"
+        every { project.extensions.findByName("android") } returns mockApplicationExtension
         every { mockCmakeOptions.path } returns null
         every { project.findProperty(FlutterPluginUtils.PROP_SDK_MANAGER_PATH) } returns "/sdkmanager"
         every { project.findProperty(FlutterPluginUtils.PROP_ANDROID_SDK_ROOT) } returns "/sdk/root"
@@ -2289,7 +2316,9 @@ class FlutterPluginUtilsTest {
         every { project.findProperty(FlutterPluginUtils.PROP_INSTALLED_NDK_VERSIONS) } returns ""
         every { project.gradle.startParameter.taskNames } returns emptyList()
         every { project.gradle.startParameter.isOffline } returns false
-        every { project.extensions.findByType(ApplicationExtension::class.java) } returns null
+        val mockAndroidExtension = mockk<ApplicationExtension>()
+        every { project.extensions.findByName("android") } returns mockAndroidExtension
+        every { mockAndroidExtension.ndkVersion } returns "29.0.13846066"
         every { project.serviceOf<ExecOperations>() } returns mockExecOperations
         every { mockExecOperations.exec(any<Action<ExecSpec>>()) } returns mockExecResult
         every { mockExecResult.assertNormalExitValue() } returns mockExecResult
@@ -2496,7 +2525,7 @@ class FlutterPluginUtilsTest {
         val project = mockk<Project>(relaxed = true)
         val androidExtension = mockk<ApplicationExtension>()
         every { androidExtension.ndkVersion } returns "29.0.13846066"
-        every { project.extensions.findByType(ApplicationExtension::class.java) } returns androidExtension
+        every { project.extensions.findByName("android") } returns androidExtension
         every { project.tasks.register(any(), eq(PrintTask::class.java), any()) } returns mockk()
         val captureSlot = slot<Action<PrintTask>>()
 

packages/flutter_tools/gradle/src/test/kotlin/VersionFetcherTest.kt

@@ -6,7 +6,6 @@ package com.flutter.gradle
 
 import com.android.build.api.AndroidPluginVersion
 import com.android.build.api.variant.AndroidComponentsExtension
-import com.flutter.gradle.testing.setAgpKotlinVersionToNull
 import io.mockk.every
 import io.mockk.mockk
 import org.gradle.api.Project
@@ -47,7 +46,6 @@ class VersionFetcherTest {
     fun `getKGPVersion returns version when kotlin_version is set`() {
         val kgpVersion = Version(1, 9, 20)
         val project = mockk<Project>()
-        setAgpKotlinVersionToNull(project)
         every { project.hasProperty(eq("kotlin_version")) } returns true
         every { project.properties["kotlin_version"] } returns kgpVersion.toString()
         val result = VersionFetcher.getKGPVersion(project)
@@ -58,7 +56,6 @@ class VersionFetcherTest {
     fun `getKGPVersion returns version from KotlinAndroidPluginWrapper`() {
         val kgpVersion = Version(1, 9, 20)
         val project = mockk<Project>()
-        setAgpKotlinVersionToNull(project)
         every { project.hasProperty(eq("kotlin_version")) } returns false
         every { project.plugins.findPlugin(KotlinAndroidPluginWrapper::class.java) } returns
             mockk<KotlinAndroidPluginWrapper> {
@@ -67,4 +64,51 @@ class VersionFetcherTest {
         val result = VersionFetcher.getKGPVersion(project)
         assertEquals(kgpVersion, result!!)
     }
+
+    @Test
+    fun `getKGPVersion returns null when the Kotlin Gradle plugin is absent`() {
+        // Expected under AGP's built-in Kotlin support, where no standalone KGP is applied.
+        val project = mockk<Project>()
+        every { project.hasProperty(eq("kotlin_version")) } returns false
+        every { project.plugins.findPlugin(KotlinAndroidPluginWrapper::class.java) } returns null
+        val result = VersionFetcher.getKGPVersion(project)
+        assertEquals(null, result)
+    }
+
+    // CompileSdkVersion.isHigherThan
+    @Test
+    fun `isHigherThan compares numeric api levels numerically`() {
+        val sdk35 = CompileSdkVersion(apiLevel = 35, previewCodename = null)
+        val sdk36 = CompileSdkVersion(apiLevel = 36, previewCodename = null)
+        assertEquals(true, sdk36.isHigherThan(sdk35))
+        assertEquals(false, sdk35.isHigherThan(sdk36))
+        assertEquals(false, sdk35.isHigherThan(sdk35))
+    }
+
+    @Test
+    fun `isHigherThan treats a preview codename as higher than any numeric api level`() {
+        val preview = CompileSdkVersion(apiLevel = null, previewCodename = "Baklava")
+        val numeric = CompileSdkVersion(apiLevel = 36, previewCodename = null)
+        assertEquals(true, preview.isHigherThan(numeric))
+        assertEquals(false, numeric.isHigherThan(preview))
+    }
+
+    @Test
+    fun `isHigherThan treats distinct preview codenames as incomparable`() {
+        // Codenames stopped being alphabetically ordered at the "Baklava" alphabet reset,
+        // so neither side may claim to be higher.
+        val baklava = CompileSdkVersion(apiLevel = null, previewCodename = "Baklava")
+        val vanilla = CompileSdkVersion(apiLevel = null, previewCodename = "VanillaIceCream")
+        assertEquals(false, baklava.isHigherThan(vanilla))
+        assertEquals(false, vanilla.isHigherThan(baklava))
+        assertEquals(false, baklava.isHigherThan(baklava))
+    }
+
+    @Test
+    fun `isHigherThan returns false when either side is unset`() {
+        val unset = CompileSdkVersion(apiLevel = null, previewCodename = null)
+        val numeric = CompileSdkVersion(apiLevel = 36, previewCodename = null)
+        assertEquals(false, unset.isHigherThan(numeric))
+        assertEquals(false, numeric.isHigherThan(unset))
+    }
 }