Capture two folders in prerequisite for Makefile's target - shell

Question

For my Makefile, my prerequisite is of the form
$(Root)a/b/c/d/File.source
and I'd like to target
a/c.zip
knowing that there are multiple folders for a and c, that b is fixed, that d can vary, but that the source file is always called File.source.
Taking inspiration from this answer, I've tried
As:= $(notdir $(shell find $(Root) -mindepth 1 -maxdepth 1 -type d))
define RULE
$1/%.zip: $1/b/%/*/File.source
echo "Test"
endef
$(foreach a, $(As), $(eval $(call RULE, $(a))))
But it does not seem to work.

Answer 1

I think this could be relatively simple, given the fact how patterns match. Having a rule
%.zip: b/%.foo
will cause make a/c.zip to search for a/b/c.foo file. With this in mind we can write a quite simple Makefile:
$ cat Makefile
# Extract directories that contain File.source files
sourcedirs := $(dir $(wildcard $(ROOT)*/b/*/*/File.source))
# Generate archive names: drop the /b/ part and add .zip extension
archives := $(patsubst %/,%.zip,$(subst /b/,/,$(dir $(sourcedirs:/=))))
%.zip: b/%/*/File.source
echo Making $# from $<
all: $(archives)
The output:
$ find . -name File.source
./a/b/c/d/File.source
./foo/b/bar/baz/File.source
./foo/b/cfg/d/File.source
$ make -s
Making foo/bar.zip from foo/b/bar/baz/File.source
Making foo/cfg.zip from foo/b/cfg/d/File.source
Making a/c.zip from a/b/c/d/File.source

Answer 2

Let's first find all File.source files that match the $(Root)*/b/*/*/File.source pattern:
FILES := $(shell find $(Root)*/b/* -maxdepth 2 -mindepth 2 -type f -name File.source)
Then, let's create a macro for each of them (I over-exaggerated the number of intermediate variables for easier understanding, you can simplify a bit, if you wish):
# $(1): File.source path
define MY_RULE
$(1)-dirs := $$(subst /, ,$(1))
$(1)-Roota := $$(word 1,$$($(1)-dirs))
$(1)-a := $$(patsubst $$(Root)%,%,$$($(1)-Roota))
$(1)-c := $$(word 3,$$($(1)-dirs))
$(1)-target := $$($(1)-a)/$$($(1)-c).zip
$$($(1)-target): $(1)
#echo "Test for $$< (target $$#)"
endef
And finally, let's call the macro on each File.source file:
$(foreach f,$(FILES),$(eval $(call MY_RULE,$(f))))
All in all, plus a test phony default goal for easier testing:
FILES := $(shell find $(Root)*/b/* -maxdepth 2 -mindepth 2 -type f -name File.source)
.PHONY: test
.DEFAULTGOAL := test
# $(1): File.source path
define MY_RULE
$(1)-dirs := $$(subst /, ,$(1))
$(1)-Roota := $$(word 1,$$($(1)-dirs))
$(1)-a := $$(patsubst $$(Root)%,%,$$($(1)-Roota))
$(1)-c := $$(word 3,$$($(1)-dirs))
$(1)-target := $$($(1)-a)/$$($(1)-c).zip
$$($(1)-target): $(1)
#echo "Test for $$< (target $$#)"
test: $$($(1)-target)
endef
$(foreach f,$(FILES),$(eval $(call MY_RULE,$(f))))
Note: there is a possibility that you have more than one File.source file with the same corresponding target, because of the d part of your pattern. If this happens GNU make will issue warnings and use only the last encountered rule for each such target. There are ways to raise an error, if you prefer, but as all this is already quite complicated, let's leave it as an exercise on make conditionals.