Resolve metalava semver using outdated version info (#7159)

Returns to older behavior of returning to the PR branch to run the
check, to make sure gradle.properties version is updated.

Author: emilypgoogle

.github/workflows/metalava-semver-check.yml

@@ -11,8 +11,10 @@ jobs:
     permissions:
       pull-requests: write
     steps:
-      - name: Checkout PR
+      - name: Checkout main
         uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
+        with:
+          ref: ${{ github.base_ref }}
 
       - name: Set up JDK 17
         uses: actions/setup-java@3a4f6e1af504cf6a31855fa899c6aa5355ba6c12 # v4.7.0
@@ -21,13 +23,13 @@ jobs:
           distribution: temurin
           cache: gradle
 
-      - name: Copy new api.txt files
+      - name: Copy existing api.txt files
         run: ./gradlew copyApiTxtFile
 
-      - name: Checkout main
+      - name: Checkout PR
         uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
         with:
-          ref: ${{ github.base_ref }}
+          ref: ${{ github.head_ref || github.ref_name }}
           clean: false
 
       - name: Run Metalava SemVer check

plugins/src/main/java/com/google/firebase/gradle/plugins/BaseFirebaseLibraryPlugin.kt

@@ -126,6 +126,20 @@ abstract class BaseFirebaseLibraryPlugin : Plugin<Project> {
     Coverage.apply(library)
   }
 
+  protected fun setupMetalavaSemver(project: Project, library: FirebaseLibraryExtension) {
+    project.tasks.register<CopyApiTask>("copyApiTxtFile") {
+      apiTxtFile.set(project.file("api.txt"))
+      output.set(project.file("existing_api.txt"))
+    }
+
+    project.tasks.register<SemVerTask>("metalavaSemver") {
+      apiTxtFile.set(project.file("api.txt"))
+      existingApiFile.set(project.file("existing_api.txt"))
+      currentVersionString.value(library.version)
+      previousVersionString.value(library.previousVersion)
+    }
+  }
+
   protected fun getApiInfo(
     project: Project,
     srcDirs: ConfigurableFileCollection,

plugins/src/main/java/com/google/firebase/gradle/plugins/FirebaseAndroidLibraryPlugin.kt

@@ -161,17 +161,7 @@ class FirebaseAndroidLibraryPlugin : BaseFirebaseLibraryPlugin() {
       )
     }
 
-    project.tasks.register<CopyApiTask>("copyApiTxtFile") {
-      apiTxtFile.set(project.file("api.txt"))
-      output.set(project.file("new_api.txt"))
-    }
-
-    project.tasks.register<SemVerTask>("metalavaSemver") {
-      apiTxtFile.set(project.file("new_api.txt"))
-      otherApiFile.set(project.file("api.txt"))
-      currentVersionString.value(firebaseLibrary.version)
-      previousVersionString.value(firebaseLibrary.previousVersion)
-    }
+    setupMetalavaSemver(project, firebaseLibrary)
   }
 
   private fun setupApiInformationAnalysis(project: Project, android: LibraryExtension) {

plugins/src/main/java/com/google/firebase/gradle/plugins/FirebaseJavaLibraryPlugin.kt

@@ -104,17 +104,7 @@ class FirebaseJavaLibraryPlugin : BaseFirebaseLibraryPlugin() {
       dependsOn("copyPreviousArtifacts")
     }
 
-    project.tasks.register<CopyApiTask>("copyApiTxtFile") {
-      apiTxtFile.set(project.file("api.txt"))
-      output.set(project.file("new_api.txt"))
-    }
-
-    project.tasks.register<SemVerTask>("metalavaSemver") {
-      apiTxtFile.set(project.file("new_api.txt"))
-      otherApiFile.set(project.file("api.txt"))
-      currentVersionString.value(firebaseLibrary.version)
-      previousVersionString.value(firebaseLibrary.previousVersion)
-    }
+    setupMetalavaSemver(project, firebaseLibrary)
   }
 
   private fun setupApiInformationAnalysis(project: Project) {

plugins/src/main/java/com/google/firebase/gradle/plugins/SemVerTask.kt

@@ -31,7 +31,7 @@ import org.gradle.process.ExecOperations
 abstract class SemVerTask @Inject constructor(private val execOperations: ExecOperations) :
   DefaultTask() {
   @get:InputFile abstract val apiTxtFile: RegularFileProperty
-  @get:InputFile abstract val otherApiFile: RegularFileProperty
+  @get:InputFile abstract val existingApiFile: RegularFileProperty
   @get:Input abstract val currentVersionString: Property<String>
   @get:Input abstract val previousVersionString: Property<String>
 
@@ -55,7 +55,7 @@ abstract class SemVerTask @Inject constructor(private val execOperations: ExecOp
         "--source-files",
         apiTxtFile.get().asFile.absolutePath,
         "--check-compatibility:api:released",
-        otherApiFile.get().asFile.absolutePath,
+        existingApiFile.get().asFile.absolutePath,
       ) +
         MAJOR.flatMap { m -> listOf("--error", m) } +
         MINOR.flatMap { m -> listOf("--error", m) } +