It appears that the method that the uTwit property editor is using to retrieve the prevalues (the consumer and secret keys set in the data type) is not compatible with the new document type compositions in Umbraco 7.2 onwards.

If the Twitter OAuth property is added directly to a document type (presumably also if it's inherited from a parent type using the older document types structures, but I haven't tested this) then twitteroauth1callback.aspx successfully retrieves the prevalues and passes them to the twitter authorisation window, displaying the correct application details.

However, if the Twitter OAuth property is added to a document type (we'll call it a mixin to avoid confusion) which is then added to the main document type as a Document Type Composition then twitteroauth1callback.aspx fails to find the prevalues and defaults to the uTwit ones.

It looks to me like uTwitHelper.GetPreValueOptionsByAlias is using UmbracoContext.Current.Application.Services.ContentTypeService.GetContentType().PropertyTypes to retrieve the content type, and that this is failing to return the mixin property. It could be UmbracoContext.Current.Application.Services.DataTypeService.GetPreValuesCollectionByDataTypeId that's going wrong, but I can't see why this would be affected by the property being on the mixin (as it's already operating at the property type level, not document type).

Can anyone confirm whether I'm right about where this is going wrong?