Change `clean` to a double colon rule?

[ptgolden]

The templated Makefile, of course, contains a .PHONY clean target:

ontology-development-kit/template/src/ontology/Makefile.jinja2

Lines 1584 to 1591 in d045276

	.PHONY: clean
	clean:{% if project.use_dosdps %}
	$(MAKE) pattern_clean{%- endif %}
	for dir in $(MIRRORDIR) $(TMPDIR) $(UPDATEREPODIR) ; do \
	reldir=$$(realpath --relative-to=$$(pwd) $$dir) ; \
	case $$reldir in .*|"") ;; *) rm -rf $$reldir/* ;; esac \
	done
	rm -f $(CLEANFILES)

I've run into a case where that clean target is overridden in {{ project.id }}.Makefile, where a custom clean target was desired. This results in the original clean target being overwritten:

zp.Makefile:216: warning: overriding recipe for target 'clean'
Makefile:1023: warning: ignoring old recipe for target 'clean'

If the rules were defined with double colon syntax (clean::), it would be possible to run both without worrying about overrides.

(The same could possibly apply to help, if someone wanted to document additional key commands).

[ptgolden]

Of course, the easy solution would be to not conflict with the builtin-clean, and to remember to run make clean zp-clean. However, it's a nice QOL thing to have make clean clean everything you want to be cleaned.

[gouttegd]

If the rules were defined with double colon syntax (clean::), it would be possible to run both without worrying about overrides.

I am inclined to agree with this idea.

Generally, we want people to be able to override any rule in their custom Makefiles and do things differently from the built-in rule, but in the case of clean, it does seem like a good idea to ensure that the built-in rule is always executed “as is“.

[ptgolden]

If this were implemented, one thing is that the clean target in the included Makefile must use double colon syntax:

ptgolden@plap3:/tmp/make$ cat >> included.Makefile
.PHONY: clean
clean:
	@echo 'clean from included'
ptgolden@plap3:/tmp/make$ cat >> Makefile
.PHONY: clean
clean::
	@echo 'clean from main'

include included.Makefile
ptgolden@plap3:/tmp/make$ make
included.Makefile:2: *** target file 'clean' has both : and :: entries.  Stop.

As the GNU Make manual says: "Double-colon rules are somewhat obscure and not often very useful". (I actually can't think of an example where I've used them myself, except to provide multiple clean targets). It might be strange to assume people know about them. If this were implemented, it should be added as a stub to the included Makefile:

ontology-development-kit/template/_dynamic_files.jinja2

Lines 184 to 196 in d045276

	^^^ src/ontology/{{ project.id }}.Makefile
	## Customize Makefile settings for {{project.id}}
	##
	## If you need to customize your Makefile, make
	## changes here rather than in the main Makefile
	{% if project.import_group is defined -%}
	{% if 'custom' == project.import_group.module_type -%}
	imports/%_import.owl: mirror/%.owl
	echo "ERROR: You have configured your default module type to be custom; this behavior needs to be overwritten in {{ project.id }}.Makefile!" && touch $@
	{% endif -%}
	{% if project.import_group.use_base_merging -%}
	{#

For example:

.PHONY: clean
clean::
	# Add any custom cleaning routines here