if

HydratedTarget

can have only the

TargetAdaptor

field, where does the actual hydration come in?

The hydration occurs in

build_files.py

and

engine/legacy/graph.py

. We have code to parse the BUILD file entry and convert it into a

HydratedStruct

, then a

TargetAdaptor

. That’s how the

TargetAdaptor

ends up with fields like

compatibility

defined on it