if the DOCKER variable isn't defined at the point this Makefile is loaded, $(DOCKER) will evaluate to the empty string. "simple expansion", i.e. := in make, will eagerly evaluate the expression to the right, so it's possible for the ISORT/BLACK variables to be given malformed values (run --rm -it ..., missing the "docker" executable).
This change uses "recursive expansion", which delays expansion of variables until the target recipe is executed, giving DOCKER a chance to be populated.
if the
DOCKERvariable isn't defined at the point this Makefile is loaded,$(DOCKER)will evaluate to the empty string. "simple expansion", i.e.:=in make, will eagerly evaluate the expression to the right, so it's possible for the ISORT/BLACK variables to be given malformed values (run --rm -it ..., missing the "docker" executable).This change uses "recursive expansion", which delays expansion of variables until the target recipe is executed, giving
DOCKERa chance to be populated.