getDownloadUrl and getMetadata at the root of a bucket throws proper …

…error message (#445)

firebase-storage/CHANGELOG.md

@@ -4,3 +4,6 @@
   and are not mentioned in our documentation.
 - [internal] Updated the SDK initialization process and removed usages of
   deprecated methods.
+- [changed] Added validation to `StorageReference.getDownloadUrl` and 
+  `StorageReference.getMetadata` to return an error if the reference is the
+  root of the bucket.

firebase-storage/src/main/java/com/google/firebase/storage/GetDownloadUrlTask.java

@@ -43,7 +43,10 @@ class GetDownloadUrlTask implements Runnable {
 
     this.storageRef = storageRef;
     this.pendingResult = pendingResult;
-
+    if (storageRef.getRoot().getName().equals(storageRef.getName())) {
+      throw new IllegalArgumentException(
+          "getDownloadUrl() is not supported at the root of the bucket.");
+    }
     FirebaseStorage storage = this.storageRef.getStorage();
     sender =
         new ExponentialBackoffSender(

firebase-storage/src/main/java/com/google/firebase/storage/GetMetadataTask.java

@@ -41,6 +41,10 @@ class GetMetadataTask implements Runnable {
 
     this.mStorageRef = storageRef;
     this.mPendingResult = pendingResult;
+    if (storageRef.getRoot().getName().equals(storageRef.getName())) {
+      throw new IllegalArgumentException(
+          "getMetadata() is not supported at the root of the bucket.");
+    }
 
     FirebaseStorage storage = mStorageRef.getStorage();
     mSender =

firebase-storage/src/test/java/com/google/firebase/storage/StorageReferenceTest.java

@@ -263,8 +263,9 @@ public void badURL2() throws Exception {
   @Test
   public void downloadUrl() throws Exception {
     MockConnectionFactory factory = NetworkLayerMock.ensureNetworkMock("downloadUrl", true);
+    final StorageReference ref = FirebaseStorage.getInstance().getReference("flubbertest.txt");
 
-    Task<StringBuilder> task = TestCommandHelper.testDownloadUrl();
+    Task<StringBuilder> task = TestCommandHelper.testDownloadUrl(ref);
     for (int i = 0; i < 3000; i++) {
       Robolectric.flushForegroundThreadScheduler();
       if (task.isComplete()) {
@@ -277,4 +278,30 @@ public void downloadUrl() throws Exception {
     }
     Assert.fail();
   }
+
+  @Test
+  public void downloadUrlBucketRoot() throws Exception {
+    final StorageReference ref = FirebaseStorage.getInstance().getReference();
+
+    boolean thrown = false;
+    try {
+      TestCommandHelper.testDownloadUrl(ref);
+    } catch (IllegalArgumentException e) {
+      thrown = true;
+    }
+    Assert.assertTrue(thrown);
+  }
+
+  @Test
+  public void getMetadataBucketRoot() throws Exception {
+    final StorageReference ref = FirebaseStorage.getInstance().getReference();
+
+    boolean thrown = false;
+    try {
+      TestCommandHelper.getMetadata(ref);
+    } catch (IllegalArgumentException e) {
+      thrown = true;
+    }
+    Assert.assertTrue(thrown);
+  }
 }

firebase-storage/src/testUtil/java/com/google/firebase/storage/TestCommandHelper.java

@@ -35,9 +35,7 @@ public class TestCommandHelper {
 
   private static final Executor executor = ExecutorProviderHelper.getInstance();
 
-  public static Task<StringBuilder> testDownloadUrl() {
-    final StorageReference ref = FirebaseStorage.getInstance().getReference("flubbertest.txt");
-
+  public static Task<StringBuilder> testDownloadUrl(StorageReference ref) {
     TaskCompletionSource<StringBuilder> result = new TaskCompletionSource<>();
     StringBuilder builder = new StringBuilder();
     builder.append("Getting Download Url.\n");
@@ -54,7 +52,7 @@ public static Task<StringBuilder> testDownloadUrl() {
     return result.getTask();
   }
 
-  private static Task<StringBuilder> getMetadata(StorageReference ref) {
+  static Task<StringBuilder> getMetadata(StorageReference ref) {
     TaskCompletionSource<StringBuilder> result = new TaskCompletionSource<>();
     StringBuilder builder = new StringBuilder();
     builder.append("Getting Metadata.\n");