Add Metalava SemVer Task

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

@@ -0,0 +1,34 @@
+name: Metalava SemVer Check
+
+on:
+  pull_request:
+
+jobs:
+  semver-check:
+    runs-on: ubuntu-latest
+    permissions:
+      pull-requests: write
+    steps:
+      - name: Checkout main
+        uses: actions/[email protected]
+        with:
+          ref: ${{ github.base_ref }}
+
+      - name: Set up JDK 17
+        uses: actions/[email protected]
+        with:
+          java-version: 17
+          distribution: temurin
+          cache: gradle
+
+      - name: Copy previous api.txt files
+        run: ./gradlew copyApiTxtFile
+
+      - name: Checkout PR
+        uses: actions/[email protected]
+        with:
+          ref: ${{ github.head_ref }}
+          clean: false
+
+      - name: Run Metalava SemVer check
+        run: ./gradlew metalavaSemver

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

@@ -165,6 +165,14 @@ class FirebaseAndroidLibraryPlugin : BaseFirebaseLibraryPlugin() {
       apiTxtFile.set(project.file("api.txt"))
       output.set(project.file("previous_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"))
+      currentVersionString.value(firebaseLibrary.version)
+      previousVersionString.value(firebaseLibrary.previousVersion)
+    }
   }
 
   private fun setupApiInformationAnalysis(project: Project, android: LibraryExtension) {

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

@@ -108,6 +108,14 @@ class FirebaseJavaLibraryPlugin : BaseFirebaseLibraryPlugin() {
       apiTxtFile.set(project.file("api.txt"))
       output.set(project.file("previous_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"))
+      currentVersionString.value(firebaseLibrary.version)
+      previousVersionString.value(firebaseLibrary.previousVersion)
+    }
   }
 
   private fun setupApiInformationAnalysis(project: Project) {

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

@@ -55,7 +55,6 @@ fun Project.runMetalavaWithArgs(
 ) {
   val allArgs =
     listOf(
-      "--no-banner",
       "--hide",
       "HiddenSuperclass", // We allow having a hidden parent class
       "--hide",

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

@@ -0,0 +1,104 @@
+/*
+ * Copyright 2025 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.gradle.plugins
+
+import com.google.firebase.gradle.plugins.semver.VersionDelta
+import java.io.ByteArrayOutputStream
+import org.gradle.api.DefaultTask
+import org.gradle.api.GradleException
+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() {
+  @get:InputFile abstract val apiTxtFile: RegularFileProperty
+  @get:InputFile abstract val otherApiFile: RegularFileProperty
+  @get:Input abstract val currentVersionString: Property<String>
+  @get:Input abstract val previousVersionString: Property<String>
+
+  @get:OutputFile abstract val outputApiFile: RegularFileProperty
+
+  @TaskAction
+  fun run() {
+    val previous = ModuleVersion.fromStringOrNull(previousVersionString.get()) ?: return
+    val current = ModuleVersion.fromStringOrNull(currentVersionString.get()) ?: return
+
+    val bump =
+      when {
+        previous.major != current.major -> VersionDelta.MAJOR
+        previous.minor != current.minor -> VersionDelta.MINOR
+        else -> VersionDelta.PATCH
+      }
+    val stream = ByteArrayOutputStream()
+    project.runMetalavaWithArgs(
+      listOf(
+        "--source-files",
+        apiTxtFile.get().asFile.absolutePath,
+        "--check-compatibility:api:released",
+        otherApiFile.get().asFile.absolutePath,
+      ) +
+        MAJOR.flatMap { m -> listOf("--error", m) } +
+        MINOR.flatMap { m -> listOf("--error", m) } +
+        IGNORED.flatMap { m -> listOf("--hide", m) } +
+        listOf("--format=v3", "--no-color"),
+      ignoreFailure = true,
+      stdOut = stream,
+    )
+
+    val string = String(stream.toByteArray())
+    val reg = Regex("(.*)\\s+error:\\s+(.*\\s+\\[(.*)\\])")
+    val minorChanges = mutableListOf<String>()
+    val majorChanges = mutableListOf<String>()
+    for (match in reg.findAll(string)) {
+      val loc = match.groups[1]!!.value
+      val message = match.groups[2]!!.value
+      val type = match.groups[3]!!.value
+      if (IGNORED.contains(type)) {
+        continue // Shouldn't be possible
+      } else if (MINOR.contains(type)) {
+        minorChanges.add(message)
+      } else {
+        majorChanges.add(message)
+      }
+    }
+    val allChanges =
+      (majorChanges.joinToString(separator = "") { m -> "  MAJOR: $m\n" }) +
+        minorChanges.joinToString(separator = "") { m -> "  MINOR: $m\n" }
+    if (majorChanges.isNotEmpty()) {
+      if (bump != VersionDelta.MAJOR) {
+        throw GradleException(
+          "API has non-bumped breaking MAJOR changes\nCurrent version bump is ${bump}, update the gradle.properties or fix the changes\n$allChanges"
+        )
+      }
+    } else if (minorChanges.isNotEmpty()) {
+      if (bump != VersionDelta.MAJOR && bump != VersionDelta.MINOR) {
+        throw GradleException(
+          "API has non-bumped MINOR changes\nCurrent version bump is ${bump}, update the gradle.properties or fix the changes\n$allChanges"
+        )
+      }
+    }
+  }
+
+  companion object {
+    private val MAJOR = setOf("AddedFinal")
+    private val MINOR = setOf("AddedClass", "AddedMethod", "AddedField", "ChangedDeprecated")
+    private val IGNORED = setOf("ReferencesDeprecated")
+  }
+}