The NamingConvention documentation at http://breeze.github.io/doc-js/server-namingconvention.html must warn developers that the property name "entityType" cannot be used by any entity data on the client-side, because it conflicts with the metadata stored in "entityType" of each client-side record managed by breeze-client Entity. Specifically, the function serverPropertyNameToClient cannot return "entityType".

The only indication is the unhelpful "Cannot assign a navigation property in an entity ctor.: entityType" error thrown by adapter-model-library-backing-store.ts. The "entityType" property does not have to be referenced in application code. Any property name received from the server that resolves to "entityType" will trigger this issue.

In fact, you don't need a custom NamingConvention ... a server-side property named "entityType" may trigger this issue, if its host entity is included in the navigation. So there may be other places in the documentation to update.

My workaround was to explicitly exclude real-life "EntityType" and "EntityAspect" property names from being camel-cased by our custom NamingConvention, and to rename those properties in our TypeScript interfaces.