Mapperly RMG023 error: How to specify default value for mapping?

I am mapping an object (A=>B). B has a required property which is not contained in A, but is available from another source. How can I create a map and provide this value, such that I do not get an RMG023 error?

Solution

Currently, the only way is to create an instance mapper, set a property to the additional mapping source and implement an object factory setting all required properties. Additional mapping parameters is an issue requesting what you need, but will probably take some time to implement.

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