why is scons complaining "implicit dependency foo not found, needed by target bar" when foo exists?

Question

Scons is complaining

  implicit dependency foo not found, needed by target bar

foo is created in my SCons build flow, and then consumed in the creation of target bar. After foo is created, SCons complains that it doesn't exist when it re-checks the dependencies before running bar. Why is SCons caching the existence check for foo?

After I get the failure, if I remove .sconsign.dblite and rerun, SCons finds the file and keeps running.

Answer 1

The issue was that I was running with

SetOption('implicit_cache', 1)

When I comment out implicit caching, then this problem doesn't manifest. This seems to be a bug... shouldn't SCons re-check for the file if the implicit cache says the file doesn't exist?