Enable dead code elimination for vendored deps.

Author: vkryachko

buildSrc/src/main/java/com/google/firebase/gradle/plugins/VendorPlugin.kt

@@ -80,7 +80,12 @@ class VendorPlugin : Plugin<Project> {
 }
 
 interface JarTransformer {
-  fun transform(inputJar: File, outputJar: File, packagesToVendor: Set<String>)
+  fun transform(
+    inputJar: File,
+    outputJar: File,
+    ownPackages: Set<String>,
+    packagesToVendor: Set<String>
+  )
 }
 
 class JarJarTransformer(
@@ -89,10 +94,18 @@ class JarJarTransformer(
   private val project: Project,
   private val logger: Logger
 ) : JarTransformer {
-  override fun transform(inputJar: File, outputJar: File, packagesToVendor: Set<String>) {
+  override fun transform(
+    inputJar: File,
+    outputJar: File,
+    ownPackages: Set<String>,
+    packagesToVendor: Set<String>
+  ) {
     val parentPackage = parentPackageProvider()
     val rulesFile = File.createTempFile(parentPackage, ".jarjar")
     rulesFile.printWriter().use {
+      for (packageName in ownPackages) {
+        it.println("keep $packageName.**")
+      }
       for (externalPackageName in packagesToVendor) {
         it.println("rule $externalPackageName.** $parentPackage.@0")
       }
@@ -227,7 +240,7 @@ class VendorTransform(
     zipAll(unzippedDir, jar)
     val outputJar = File(workDir, "output.jar")
 
-    jarTransformer.transform(jar, outputJar, externalPackageNames)
+    jarTransformer.transform(jar, outputJar, ownPackageNames, externalPackageNames)
     return outputJar
   }
 

buildSrc/src/test/kotlin/com/google/firebase/gradle/plugins/VendorTests.kt

@@ -86,11 +86,11 @@ class VendorPluginTests {
       )
 
     // ImmutableList is not used, so it should be stripped out.
-    assertThat(classes).doesNotContain("com/google/common/collect/ImmutableList.class")
+    assertThat(classes).doesNotContain("com/example/com/google/common/collect/ImmutableList.class")
   }
 
   @Test
-  fun `vendor dagger excluding javax transitive deps and not using it should include dagger`() {
+  fun `vendor dagger excluding javax transitive deps and not using it should not include dagger`() {
     val classes =
       buildWith(
         """
@@ -113,12 +113,7 @@ class VendorPluginTests {
         )
       )
     // expected classes
-    assertThat(classes)
-      .containsAtLeast(
-        "com/example/Hello.class",
-        "com/example/BuildConfig.class",
-        "com/example/dagger/Lazy.class"
-      )
+    assertThat(classes).containsExactly("com/example/Hello.class", "com/example/BuildConfig.class")
   }
 
   @Test