AAPT2: Be more strict parsing references

Change-Id: I3d54a519687fff1e66acb8e395ef99ba01a1b845
diff --git a/tools/aapt2/ResourceUtils_test.cpp b/tools/aapt2/ResourceUtils_test.cpp
index 7de8f41..3d2a6e1 100644
--- a/tools/aapt2/ResourceUtils_test.cpp
+++ b/tools/aapt2/ResourceUtils_test.cpp
@@ -90,6 +90,26 @@
                                                   &privateRef));
 }
 
+TEST(ResourceUtilsTest, ParseAttributeReferences) {
+    EXPECT_TRUE(ResourceUtils::isAttributeReference(u"?android"));
+    EXPECT_TRUE(ResourceUtils::isAttributeReference(u"?android:foo"));
+    EXPECT_TRUE(ResourceUtils::isAttributeReference(u"?attr/foo"));
+    EXPECT_TRUE(ResourceUtils::isAttributeReference(u"?android:attr/foo"));
+}
+
+TEST(ResourceUtilsTest, FailParseIncompleteReference) {
+    EXPECT_FALSE(ResourceUtils::isAttributeReference(u"?style/foo"));
+    EXPECT_FALSE(ResourceUtils::isAttributeReference(u"?android:style/foo"));
+    EXPECT_FALSE(ResourceUtils::isAttributeReference(u"?android:"));
+    EXPECT_FALSE(ResourceUtils::isAttributeReference(u"?android:attr/"));
+    EXPECT_FALSE(ResourceUtils::isAttributeReference(u"?:attr/"));
+    EXPECT_FALSE(ResourceUtils::isAttributeReference(u"?:attr/foo"));
+    EXPECT_FALSE(ResourceUtils::isAttributeReference(u"?:/"));
+    EXPECT_FALSE(ResourceUtils::isAttributeReference(u"?:/foo"));
+    EXPECT_FALSE(ResourceUtils::isAttributeReference(u"?attr/"));
+    EXPECT_FALSE(ResourceUtils::isAttributeReference(u"?/foo"));
+}
+
 TEST(ResourceUtilsTest, ParseStyleParentReference) {
     const ResourceName kAndroidStyleFooName = { u"android", ResourceType::kStyle, u"foo" };
     const ResourceName kStyleFooName = { {}, ResourceType::kStyle, u"foo" };