Fix string lookups asserting or failing with unsupported collections

A recent change from [0] added an assert when a string lookup was
performed on a collection item with no name-property,
but silently failed with release builds.

This isn't correct in a couple of ways.
The assert makes it seem like the RNA API needs to be updated when
it's in fact valid to have collection items without a name-property.
It also misleads script authors to silently fail since it implies a
key that exists would return a result.

Raise a TypeError exception when string lookups are attempted on
collections that don't support them.

This change also applies to get() & __contains__().

[0]: 5bb3a3f157

source/blender/makesrna/RNA_access.h

@@ -433,6 +433,12 @@ int RNA_property_collection_lookup_string_index(
 
 bool RNA_property_collection_lookup_int_has_fn(PropertyRNA *prop);
 bool RNA_property_collection_lookup_string_has_fn(PropertyRNA *prop);
+bool RNA_property_collection_lookup_string_has_nameprop(PropertyRNA *prop);
+/**
+ * Return true when this type supports string lookups,
+ * it has a lookup function or it's type has a name property.
+ */
+bool RNA_property_collection_lookup_string_supported(PropertyRNA *prop);
 
 /**
  * Zero return is an assignment error.

source/blender/makesrna/intern/rna_access.cc

@@ -4237,6 +4237,19 @@ bool RNA_property_collection_lookup_string_has_fn(PropertyRNA *prop)
   return cprop->lookupstring != nullptr;
 }
 
+bool RNA_property_collection_lookup_string_has_nameprop(PropertyRNA *prop)
+{
+  BLI_assert(RNA_property_type(prop) == PROP_COLLECTION);
+  CollectionPropertyRNA *cprop = (CollectionPropertyRNA *)rna_ensure_property(prop);
+  return (cprop->item_type && cprop->item_type->nameproperty);
+}
+
+bool RNA_property_collection_lookup_string_supported(PropertyRNA *prop)
+{
+  return (RNA_property_collection_lookup_string_has_fn(prop) ||
+          RNA_property_collection_lookup_string_has_nameprop(prop));
+}
+
 int RNA_property_collection_lookup_int(PointerRNA *ptr,
                                        PropertyRNA *prop,
                                        int key,

source/blender/python/intern/bpy_rna.c

@@ -2235,6 +2235,27 @@ static int pyrna_prop_collection_subscript_is_valid_or_error(const PyObject *val
   return 0;
 }
 
+static void pyrna_prop_collection_string_subscript_unsupported_error(BPy_PropertyRNA *self,
+                                                                     const char *error_prefix)
+{
+  PyErr_Format(PyExc_TypeError,
+               "%.200s: %.200s.%.200s does not support string lookups",
+               error_prefix,
+               RNA_struct_identifier(self->ptr.type),
+               RNA_property_identifier(self->prop));
+}
+
+static int pyrna_prop_collection_string_subscript_supported_or_error(BPy_PropertyRNA *self,
+                                                                     const char *error_prefix)
+{
+  BLI_assert(BPy_PropertyRNA_Check(self));
+  if (RNA_property_collection_lookup_string_supported(self->prop)) {
+    return 0;
+  }
+  pyrna_prop_collection_string_subscript_unsupported_error(self, error_prefix);
+  return -1;
+}
+
 /* Internal use only. */
 static PyObject *pyrna_prop_collection_subscript_int(BPy_PropertyRNA *self, Py_ssize_t keynum)
 {
@@ -2360,7 +2381,7 @@ static PyObject *pyrna_prop_collection_subscript_str(BPy_PropertyRNA *self, cons
       return pyrna_struct_CreatePyObject(&newptr);
     }
   }
-  else {
+  else if (RNA_property_collection_lookup_string_has_nameprop(self->prop)) {
     /* No callback defined, just iterate and find the nth item. */
     const int keylen = strlen(keyname);
     char name[256];
@@ -2371,13 +2392,10 @@ static PyObject *pyrna_prop_collection_subscript_str(BPy_PropertyRNA *self, cons
     RNA_property_collection_begin(&self->ptr, self->prop, &iter);
     for (int i = 0; iter.valid; RNA_property_collection_next(&iter), i++) {
       PropertyRNA *nameprop = RNA_struct_name_property(iter.ptr.type);
-      BLI_assert_msg(
-          nameprop,
-          "Attempted to use a string to index into a collection of items with no 'nameproperty'.");
-      if (nameprop == NULL) {
-        /* For non-debug builds, bail if there's no 'nameproperty' to check. */
-        break;
-      }
+      /* The #RNA_property_collection_lookup_string_has_nameprop check should account for this.
+       * Although it's technically possible a sub-type clears the name property,
+       * this seems unlikely. */
+      BLI_assert(nameprop != NULL);
       char *nameptr = RNA_property_string_get_alloc(
           &iter.ptr, nameprop, name, sizeof(name), &namelen);
       if ((keylen == namelen) && STREQ(nameptr, keyname)) {
@@ -2402,6 +2420,10 @@ static PyObject *pyrna_prop_collection_subscript_str(BPy_PropertyRNA *self, cons
       return result;
     }
   }
+  else {
+    pyrna_prop_collection_string_subscript_unsupported_error(self, "bpy_prop_collection[key]");
+    return NULL;
+  }
 
   PyErr_Format(PyExc_KeyError, "bpy_prop_collection[key]: key \"%.200s\" not found", keyname);
   return NULL;
@@ -3349,6 +3371,10 @@ static int pyrna_prop_collection_contains(BPy_PropertyRNA *self, PyObject *key)
   if (RNA_property_collection_lookup_string(&self->ptr, self->prop, keyname, &newptr)) {
     return 1;
   }
+  if (pyrna_prop_collection_string_subscript_supported_or_error(
+          self, "bpy_prop_collection.__contains__") == -1) {
+    return -1;
+  }
 
   return 0;
 }
@@ -5109,6 +5135,10 @@ static PyObject *pyrna_prop_collection_get(BPy_PropertyRNA *self, PyObject *args
     if (RNA_property_collection_lookup_string(&self->ptr, self->prop, key, &newptr)) {
       return pyrna_struct_CreatePyObject(&newptr);
     }
+    if (pyrna_prop_collection_string_subscript_supported_or_error(
+            self, "bpy_prop_collection.get") == -1) {
+      return NULL;
+    }
   }
   else if (PyTuple_Check(key_ob)) {
     PyObject *ret = pyrna_prop_collection_subscript_str_lib_pair(