  A complete one-loop matching calculation for real singlet scalar extensions
of the Standard Model to the Standard Model effective field theory (SMEFT) of
dimension-six operators is presented. We compare our analytic results obtained
by using Feynman diagrams to the expressions derived in the literature by a
combination of the universal one-loop effective action (UOLEA) approach and
Feynman calculus. After identifying contributions that have been overlooked in
the existing calculations, we find that the pure diagrammatic approach and the
mixed method lead to identical results. We highlight some of the subtleties
involved in computing one-loop matching corrections in SMEFT.
