Adjust Metalava SemVer task (#6846)

Reverses the order in which branches and comparisons are done. This will
mean the actual test behavior lags behind by one commit, so to test this
I will open a PR to this branch not to be merged with example changes.

See test success here
#6849

---------

Co-authored-by: Rodrigo Lazo <[email protected]>

Author: emilypgoogle

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

@@ -9,10 +9,8 @@ jobs:
     permissions:
       pull-requests: write
     steps:
-      - name: Checkout main
+      - name: Checkout PR
         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 +19,13 @@ jobs:
           distribution: temurin
           cache: gradle
 
-      - name: Copy previous api.txt files
+      - name: Copy new api.txt files
         run: ./gradlew copyApiTxtFile
 
-      - name: Checkout PR
+      - name: Checkout main
         uses: actions/checkout@11bd71901bbe5b1630ceea73d27597364c9af683 # v4.2.2
         with:
-          ref: ${{ github.head_ref }}
+          ref: ${{ github.base_ref }}
           clean: false
 
       - name: Run Metalava SemVer check

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

@@ -163,13 +163,12 @@ class FirebaseAndroidLibraryPlugin : BaseFirebaseLibraryPlugin() {
 
     project.tasks.register<CopyApiTask>("copyApiTxtFile") {
       apiTxtFile.set(project.file("api.txt"))
-      output.set(project.file("previous_api.txt"))
+      output.set(project.file("new_api.txt"))
     }
 
     project.tasks.register<SemVerTask>("metalavaSemver") {
-      apiTxtFile.set(project.file("api.txt"))
-      otherApiFile.set(project.file("previous_api.txt"))
-      outputApiFile.set(project.file("opi.txt"))
+      apiTxtFile.set(project.file("new_api.txt"))
+      otherApiFile.set(project.file("api.txt"))
       currentVersionString.value(firebaseLibrary.version)
       previousVersionString.value(firebaseLibrary.previousVersion)
     }

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

@@ -106,13 +106,12 @@ class FirebaseJavaLibraryPlugin : BaseFirebaseLibraryPlugin() {
 
     project.tasks.register<CopyApiTask>("copyApiTxtFile") {
       apiTxtFile.set(project.file("api.txt"))
-      output.set(project.file("previous_api.txt"))
+      output.set(project.file("new_api.txt"))
     }
 
     project.tasks.register<SemVerTask>("metalavaSemver") {
-      apiTxtFile.set(project.file("api.txt"))
-      otherApiFile.set(project.file("previous_api.txt"))
-      outputApiFile.set(project.file("opi.txt"))
+      apiTxtFile.set(project.file("new_api.txt"))
+      otherApiFile.set(project.file("api.txt"))
       currentVersionString.value(firebaseLibrary.version)
       previousVersionString.value(firebaseLibrary.previousVersion)
     }

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

@@ -24,7 +24,6 @@ import org.gradle.api.file.RegularFileProperty
 import org.gradle.api.provider.Property
 import org.gradle.api.tasks.Input
 import org.gradle.api.tasks.InputFile
-import org.gradle.api.tasks.OutputFile
 import org.gradle.api.tasks.TaskAction
 
 abstract class SemVerTask : DefaultTask() {
@@ -33,7 +32,7 @@ abstract class SemVerTask : DefaultTask() {
   @get:Input abstract val currentVersionString: Property<String>
   @get:Input abstract val previousVersionString: Property<String>
 
-  @get:OutputFile abstract val outputApiFile: RegularFileProperty
+  // TODO cache output
 
   @TaskAction
   fun run() {