The CREATE FUNCTION statement allows for specifying "WITH RETURNS NULL ON NULL INPUT" that, if set, causes the function to return NULL and not get executed if any input parameter is set to NULL. This is a wonderful and important option, especially with SQLCLR functions that accept SqlString input parameters since their value is transferred to the AppDomain upon being executed. This is a waste of CPU and memory if you know that the function will simply exit and not make use of that string value.
Unfortunately, when using SSDT, there is no way to set this option in the source code. The only way to accomplish this is to issue an ALTER FUNCTION statement in a Post-Deployment SQL Script. But that is a brittle solution as it will break if changes are made to the function name, parameter names and/or datatypes, or the number of parameters. Hence it is one more thing to maintain.