-override id = $(or $(shell $(XMLLINT) --xpath '/*/*[local-name()="id" and namespace-uri()="urn:fdc:ladys.computer:20231231:Shu1She4"]/text()[1]' $1),about:shushe?$(or $2,unknown)=$(call pathenc,$(basename $(notdir $1))))
+override id = $(or $(shell $(XMLLINT) --xpath '/*/*[local-name()="id" and namespace-uri()="urn:fdc:ladys.computer:20231231:Shu1She4"]/text()[1]' $1 2> /dev/null),about:shushe?$(or $2,unknown)=$(call pathenc,$(basename $(notdir $1))))
+
+# Pair each source magic file with its location in the build directory.
+override magicpair := $(foreach magicfile,$(MAGIC),$(magicfile)|$(BUILDDIR)/magic/$(notdir $(magicfile)))
+
+# (callable) Get the source file for the given magic files.
+override magicsource = $(foreach magicpath,$1,$(patsubst %|$(magicpath),%,$(firstword $(filter %|$(magicpath),$(magicpair)))))
+
+# (callable) Get the build file for the given magic files.
+override magicfile = $(foreach file,$1,$(patsubst $(file)|%,%,$(filter $(file)|%,$(magicpair))))