AAPT2: Allow undefined resources (placeholders)
A resource defined like so:
<item type="drawable" name="foo" />
should be assigned the value @null.
The only exception is for <string> resources, which are given the
empty string value (since <string></string> is ambiguous). The decision
to use "" is based off the fact that old AAPT used to assign "" to all
undefined resources, even non-string ones.
Bug: 38425050
Test: make aapt2_tests
Change-Id: Ib3e0f6f83d16ddd8b279c9fd44a07a37867b85e9
diff --git a/tools/aapt2/ResourceUtils.h b/tools/aapt2/ResourceUtils.h
index da0fc8e..36f6c2b 100644
--- a/tools/aapt2/ResourceUtils.h
+++ b/tools/aapt2/ResourceUtils.h
@@ -133,7 +133,16 @@
* Returns a BinaryPrimitve object representing @null or @empty if the string
* was parsed as one.
*/
-std::unique_ptr<BinaryPrimitive> TryParseNullOrEmpty(const android::StringPiece& str);
+std::unique_ptr<Item> TryParseNullOrEmpty(const android::StringPiece& str);
+
+// Returns a Reference representing @null.
+// Due to runtime compatibility issues, this is encoded as a reference with ID 0.
+// The runtime will convert this to TYPE_NULL.
+std::unique_ptr<Reference> MakeNull();
+
+// Returns a BinaryPrimitive representing @empty. This is encoded as a Res_value with
+// type Res_value::TYPE_NULL and data Res_value::DATA_NULL_EMPTY.
+std::unique_ptr<BinaryPrimitive> MakeEmpty();
/*
* Returns a BinaryPrimitve object representing a color if the string was parsed