Bugfix [#34836] Crash when driver variable has path == 'data'

Most of the places which relied on RNA_path_resolve() did so believing that if
it returned true, that it had found a valid property, and that the returned
pointer+property combination would be what the path referred to. However, it
turns out that if the property at the end of the path turns out to be a
"pointer" property (e.g. "data" for Object.data), this would automatically
become the pointer part, while the prop part would be set to null. Hence, if a
user accidentally (or otherwise) specifies a path for the single-property driver
variable type like this, then Blender would crash.

This commit introduces two convenience functions - RNA_path_resolve_property()
and RNA_path_resolve_property_full() - which mirror/wrap the existing
RNA_path_resolve() functions. The only difference though is that these include a
check to ensure that what was found from resolving the path was in fact a
property (they only return true iff this is the case), and make it explicitly
clear in the name that this is what they will do so that there's no further
confusion. It is possible to do without these wrapper functions by doing these
checks inline, but the few cases that had been patched already were pretty
hideous looking specimens. Using these just make it clearer and simpler for all.

I've also beefed up the docs on these a bit, and changed these to using bools.

2 files changed, 42 insertions, 7 deletions

diff --git a/source/blender/makesrna/RNA_access.h b/source/blender/makesrna/RNA_access.h
index 7d817f3dbe0..a61a9b3da85 100644
--- a/source/blender/makesrna/RNA_access.h
+++ b/source/blender/makesrna/RNA_access.h
@@ -898,10 +898,18 @@ char *RNA_path_append(const char *path, PointerRNA *ptr, PropertyRNA *prop,
                       int intkey, const char *strkey);
 char *RNA_path_back(const char *path);
 
-int RNA_path_resolve(PointerRNA *ptr, const char *path,
+/* path_resolve() variants only ensure that a valid pointer (and optionally property) exist */
+bool RNA_path_resolve(PointerRNA *ptr, const char *path,
                      PointerRNA *r_ptr, PropertyRNA **r_prop);
 
-int RNA_path_resolve_full(PointerRNA *ptr, const char *path,
+bool RNA_path_resolve_full(PointerRNA *ptr, const char *path,
+                          PointerRNA *r_ptr, PropertyRNA **r_prop, int *index);
+						  
+/* path_resolve_property() variants ensure that pointer + property both exist */
+bool RNA_path_resolve_property(PointerRNA *ptr, const char *path,
+                     PointerRNA *r_ptr, PropertyRNA **r_prop);
+
+bool RNA_path_resolve_property_full(PointerRNA *ptr, const char *path,
                           PointerRNA *r_ptr, PropertyRNA **r_prop, int *index);
 
 char *RNA_path_from_ID_to_struct(PointerRNA *ptr);
diff --git a/source/blender/makesrna/intern/rna_access.c b/source/blender/makesrna/intern/rna_access.c
index 9f36131a6c9..9a102c823a9 100644
--- a/source/blender/makesrna/intern/rna_access.c
+++ b/source/blender/makesrna/intern/rna_access.c
@@ -630,7 +630,7 @@ PropertyRNA *RNA_struct_find_property(PointerRNA *ptr, const char *identifier)
 		/* id prop lookup, not so common */
 		PropertyRNA *r_prop = NULL;
 		PointerRNA r_ptr; /* only support single level props */
-		if (RNA_path_resolve(ptr, identifier, &r_ptr, &r_prop) && r_ptr.type == ptr->type && r_ptr.data == ptr->data)
+		if (RNA_path_resolve(ptr, identifier, &r_ptr, &r_prop) && (r_ptr.type == ptr->type) && (r_ptr.data == ptr->data))
 			return r_prop;
 	}
 	else {
@@ -1533,7 +1533,7 @@ bool RNA_property_path_from_ID_check(PointerRNA *ptr, PropertyRNA *prop)
 		PropertyRNA *r_prop;
 
 		RNA_id_pointer_create(ptr->id.data, &id_ptr);
-		if (RNA_path_resolve(&id_ptr, path, &r_ptr, &r_prop) == TRUE) {
+		if (RNA_path_resolve(&id_ptr, path, &r_ptr, &r_prop) == true) {
 			ret = (prop == r_prop);
 		}
 		MEM_freeN(path);
@@ -3791,13 +3791,40 @@ static int rna_token_strip_quotes(char *token)
 	return 0;
 }
 
-/* Resolve the given RNA path to find the pointer+property indicated at the end of the path */
-int RNA_path_resolve(PointerRNA *ptr, const char *path, PointerRNA *r_ptr, PropertyRNA **r_prop)
+/* Resolve the given RNA Path to find both the pointer AND property indicated by fully resolving the path
+ * ! This is a convenience method to avoid logic errors and ugly syntax
+ * ! Assumes all pointers provided are valid
+ * > returns: True only if both a valid pointer and property are found after resolving the path 
+ */
+bool RNA_path_resolve_property(PointerRNA *ptr, const char *path, PointerRNA *r_ptr, PropertyRNA **r_prop)
+{
+	return RNA_path_resolve_full(ptr, path, r_ptr, r_prop, NULL) && (*r_prop != NULL);
+}
+
+/* Resolve the given RNA Path to find the pointer AND property (as well as the array index) indicated by fully resolving the path
+ * ! This is a convenience method to avoid logic errors and ugly syntax
+ * ! Assumes all pointers provided are valid
+ * > returns: True only if both a valid pointer and property are found after resolving the path
+ */
+bool RNA_path_resolve_property_full(PointerRNA *ptr, const char *path, PointerRNA *r_ptr, PropertyRNA **r_prop, int *index)
+{
+	return RNA_path_resolve_full(ptr, path, r_ptr, r_prop, index) && (*r_prop != NULL);
+}
+
+/* Resolve the given RNA Path to find the pointer and/or property indicated by fully resolving the path 
+ * ! Assumes all pointers provided are valid
+ * > returns: True if path can be resolved to a valid "pointer + property" OR "pointer only"
+ */
+bool RNA_path_resolve(PointerRNA *ptr, const char *path, PointerRNA *r_ptr, PropertyRNA **r_prop)
 {
 	return RNA_path_resolve_full(ptr, path, r_ptr, r_prop, NULL);
 }
 
-int RNA_path_resolve_full(PointerRNA *ptr, const char *path, PointerRNA *r_ptr, PropertyRNA **r_prop, int *index)
+/* Resolve the given RNA Path to find the pointer and/or property + array index indicated by fully resolving the path 
+ * ! Assumes all pointers provided are valid
+ * > returns: True if path can be resolved to a valid "pointer + property" OR "pointer only"
+ */
+bool RNA_path_resolve_full(PointerRNA *ptr, const char *path, PointerRNA *r_ptr, PropertyRNA **r_prop, int *index)
 {
 	PropertyRNA *prop;
 	PointerRNA curptr;