I'm getting an error when uploading my customized policy, which is based on Microsoft's SocialAccounts example ([tenant] is a placeholder I added):
Policy "B2C_1A_TrustFrameworkExtensions" of tenant "[tenant].onmicrosoft.com" makes a reference to ClaimType with id "client_id" but neither the policy nor any of its base policies contain such an element
I've done some customization to the file, including adding local account signon, but comparing copies of TrustFrameworkExtensions.xml in the examples, I can't see where this element is defined. It is not defined in TrustFrameworkBase.xml, which is where I would expect it.
I figured it out, although it doesn't make sense to me. Hopefully this helps someone else running into the same issue.
The TrustFrameworkBase.xml is not the same in each scenario. When Microsoft documentation said not to modify it, I assumed that meant the "base" was always the same. The implication of this design is: If you try to mix and match between scenarios then you also need to find the supporting pieces in the TrustFrameworkBase.xml and move them into your extensions document. It also means if Microsoft does provide an update to their reference policies and you want to update, you need to remember which one you implemented originally and potentially which other ones you had to pull from or do line-by-line comparison. Not end of the world, but also not how I'd design an inheritance structure.
This also explains why I had to work through previous validation errors, including missing <DisplayName> and <Protocol> elements in the <TechnicalProfile> element.