Downgrade kotlin version in firebase-dataconnect/gradleplugin from 1.9.25 to 1.8.22 to match the version used in ../../buildSrc

Author: dconeybe

firebase-dataconnect/gradleplugin/gradle/libs.versions.toml

@@ -1,6 +1,6 @@
 [versions]
 androidGradlePlugin = "8.2.1"
-kotlin = "1.9.25"
+kotlin = "1.8.22"
 
 [libraries]
 android-gradlePlugin-api = { group = "com.android.tools.build", name = "gradle-api", version.ref = "androidGradlePlugin" }

firebase-dataconnect/gradleplugin/plugin/src/main/java/com/google/firebase/dataconnect/gradle/plugin/TransformerInterop.java

@@ -0,0 +1,35 @@
+/*
+ * Copyright 2024 Google LLC
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package com.google.firebase.dataconnect.gradle.plugin;
+
+import org.gradle.api.Transformer;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+// TODO: Remove this interface and use Transformer directly once the Kotlin version is upgraded to
+// a later version that doesn't require it, such as 1.9.25. Using this interface works around the
+// following Kotlin compiler error:
+//
+// > Task :plugin:compileKotlin FAILED
+// e: DataConnectGradlePlugin.kt:93:15 Type mismatch: inferred type is RegularFile? but TypeVariable(S) was expected
+// e: DataConnectGradlePlugin.kt:102:15 Type mismatch: inferred type is String? but TypeVariable(S) was expected
+// e: DataConnectGradlePlugin.kt:111:15 Type mismatch: inferred type is DataConnectExecutable.VerificationInfo? but TypeVariable(S) was expected
+public interface TransformerInterop<OUT, IN> extends Transformer<OUT, IN> {
+
+    @Override
+    @Nullable OUT transform(@NotNull IN in);
+
+}

firebase-dataconnect/gradleplugin/plugin/src/main/kotlin/com/google/firebase/dataconnect/gradle/plugin/DataConnectGradlePlugin.kt

@@ -26,7 +26,6 @@ import java.util.Locale
 import org.gradle.api.Plugin
 import org.gradle.api.Project
 import org.gradle.api.file.Directory
-import org.gradle.api.file.RegularFile
 import org.gradle.api.logging.Logging
 import org.gradle.api.plugins.ExtensionAware
 import org.gradle.api.provider.Provider
@@ -89,31 +88,38 @@ abstract class DataConnectGradlePlugin : Plugin<Project> {
           val dataConnectExecutable = dataConnectProviders.dataConnectExecutable
           buildDirectory.set(baseBuildDirectory.map { it.dir("executable") })
           inputFile.set(
-            dataConnectExecutable.map {
-              when (it) {
-                is DataConnectExecutable.File -> project.layout.projectDirectory.file(it.file.path)
-                is DataConnectExecutable.RegularFile -> it.file
-                is DataConnectExecutable.Version -> null
+            dataConnectExecutable.map(
+              TransformerInterop {
+                when (it) {
+                  is DataConnectExecutable.File ->
+                    project.layout.projectDirectory.file(it.file.path)
+                  is DataConnectExecutable.RegularFile -> it.file
+                  is DataConnectExecutable.Version -> null
+                }
               }
-            }
+            )
           )
           version.set(
-            dataConnectExecutable.map {
-              when (it) {
-                is DataConnectExecutable.File -> null
-                is DataConnectExecutable.RegularFile -> null
-                is DataConnectExecutable.Version -> it.version
+            dataConnectExecutable.map(
+              TransformerInterop {
+                when (it) {
+                  is DataConnectExecutable.File -> null
+                  is DataConnectExecutable.RegularFile -> null
+                  is DataConnectExecutable.Version -> it.version
+                }
               }
-            }
+            )
           )
           verificationInfo.set(
-            dataConnectExecutable.map {
-              when (it) {
-                is DataConnectExecutable.File -> it.verificationInfo
-                is DataConnectExecutable.RegularFile -> it.verificationInfo
-                is DataConnectExecutable.Version -> it.verificationInfo
+            dataConnectExecutable.map(
+              TransformerInterop {
+                when (it) {
+                  is DataConnectExecutable.File -> it.verificationInfo
+                  is DataConnectExecutable.RegularFile -> it.verificationInfo
+                  is DataConnectExecutable.Version -> it.verificationInfo
+                }
               }
-            }
+            )
           )
           outputFile.set(
             dataConnectExecutable.map {