Merge "AAPT2: Be more strict parsing references"
diff --git a/tools/aapt2/ResourceUtils.cpp b/tools/aapt2/ResourceUtils.cpp
index d3c3c10..b1a4c7d 100644
--- a/tools/aapt2/ResourceUtils.cpp
+++ b/tools/aapt2/ResourceUtils.cpp
@@ -23,22 +23,28 @@
 namespace aapt {
 namespace ResourceUtils {
 
-void extractResourceName(const StringPiece16& str, StringPiece16* outPackage,
+bool extractResourceName(const StringPiece16& str, StringPiece16* outPackage,
                          StringPiece16* outType, StringPiece16* outEntry) {
+    bool hasPackageSeparator = false;
+    bool hasTypeSeparator = false;
     const char16_t* start = str.data();
     const char16_t* end = start + str.size();
     const char16_t* current = start;
     while (current != end) {
         if (outType->size() == 0 && *current == u'/') {
+            hasTypeSeparator = true;
             outType->assign(start, current - start);
             start = current + 1;
         } else if (outPackage->size() == 0 && *current == u':') {
+            hasPackageSeparator = true;
             outPackage->assign(start, current - start);
             start = current + 1;
         }
         current++;
     }
     outEntry->assign(start, end - start);
+
+    return !(hasPackageSeparator && outPackage->empty()) && !(hasTypeSeparator && outType->empty());
 }
 
 bool tryParseReference(const StringPiece16& str, ResourceNameRef* outRef, bool* outCreate,
@@ -62,26 +68,34 @@
         StringPiece16 package;
         StringPiece16 type;
         StringPiece16 entry;
-        extractResourceName(trimmedStr.substr(offset, trimmedStr.size() - offset), &package, &type,
-                            &entry);
+        if (!extractResourceName(trimmedStr.substr(offset, trimmedStr.size() - offset),
+                                 &package, &type, &entry)) {
+            return false;
+        }
 
         const ResourceType* parsedType = parseResourceType(type);
         if (!parsedType) {
             return false;
         }
 
+        if (entry.empty()) {
+            return false;
+        }
+
         if (create && *parsedType != ResourceType::kId) {
             return false;
         }
 
-        if (outRef != nullptr) {
+        if (outRef) {
             outRef->package = package;
             outRef->type = *parsedType;
             outRef->entry = entry;
         }
+
         if (outCreate) {
             *outCreate = create;
         }
+
         if (outPrivate) {
             *outPrivate = priv;
         }
@@ -104,20 +118,33 @@
         StringPiece16 package;
         StringPiece16 type;
         StringPiece16 entry;
-        extractResourceName(trimmedStr.substr(1, trimmedStr.size() - 1), &package, &type, &entry);
+        if (!extractResourceName(trimmedStr.substr(1, trimmedStr.size() - 1),
+                                 &package, &type, &entry)) {
+            return false;
+        }
 
         if (!type.empty() && type != u"attr") {
             return false;
         }
 
-        outRef->package = package;
-        outRef->type = ResourceType::kAttr;
-        outRef->entry = entry;
+        if (entry.empty()) {
+            return false;
+        }
+
+        if (outRef) {
+            outRef->package = package;
+            outRef->type = ResourceType::kAttr;
+            outRef->entry = entry;
+        }
         return true;
     }
     return false;
 }
 
+bool isAttributeReference(const StringPiece16& str) {
+    return tryParseAttributeReference(str, nullptr);
+}
+
 /*
  * Style parent's are a bit different. We accept the following formats:
  *
diff --git a/tools/aapt2/ResourceUtils.h b/tools/aapt2/ResourceUtils.h
index 851edc8..34daa66 100644
--- a/tools/aapt2/ResourceUtils.h
+++ b/tools/aapt2/ResourceUtils.h
@@ -34,8 +34,9 @@
  *
  * where the package can be empty. Validation must be performed on each
  * individual extracted piece to verify that the pieces are valid.
+ * Returns false if there was no package but a ':' was present.
  */
-void extractResourceName(const StringPiece16& str, StringPiece16* outPackage,
+bool extractResourceName(const StringPiece16& str, StringPiece16* outPackage,
                          StringPiece16* outType, StringPiece16* outEntry);
 
 /*
@@ -54,12 +55,17 @@
 bool isReference(const StringPiece16& str);
 
 /*
- * Returns true if the string was parsed as an attribute reference (?[package:]type/name),
+ * Returns true if the string was parsed as an attribute reference (?[package:][type/]name),
  * with `outReference` set to the parsed reference.
  */
 bool tryParseAttributeReference(const StringPiece16& str, ResourceNameRef* outReference);
 
 /**
+ * Returns true if the string is in the form of an attribute reference(?[package:][type/]name).
+ */
+bool isAttributeReference(const StringPiece16& str);
+
+/**
  * Returns true if the value is a boolean, putting the result in `outValue`.
  */
 bool tryParseBool(const StringPiece16& str, bool* outValue);
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" };