Fix rebuild on Makefile change when new deps are added

The issue was that when a new dep is added the last-makefile-change
update was done in the dependency and not in the top-level Makefile,
preventing the rebuild of the top-level project.

A test was also added to do the same when editing dependencies and
things seem to work properly in that case.

Thanks to robinchew on IRC for the great help debugging this.

core/erlc.mk

@@ -269,6 +269,7 @@ $(PROJECT).d:: $(ERL_FILES) $(call core_find,include/,*.hrl) $(MAKEFILE_LIST)
 	$(makedep_verbose) $(call erlang,$(call makedep.erl,$@))
 endif
 
+ifeq ($(IS_APP)$(IS_DEP),)
 ifneq ($(words $(ERL_FILES) $(CORE_FILES) $(ASN1_FILES) $(MIB_FILES) $(XRL_FILES) $(YRL_FILES)),0)
 # Rebuild everything when the Makefile changes.
 $(ERLANG_MK_TMP)/last-makefile-change: $(MAKEFILE_LIST) | $(ERLANG_MK_TMP)
@@ -281,6 +282,7 @@ $(ERLANG_MK_TMP)/last-makefile-change: $(MAKEFILE_LIST) | $(ERLANG_MK_TMP)
 $(ERL_FILES) $(CORE_FILES) $(ASN1_FILES) $(MIB_FILES) $(XRL_FILES) $(YRL_FILES):: $(ERLANG_MK_TMP)/last-makefile-change
 ebin/$(PROJECT).app:: $(ERLANG_MK_TMP)/last-makefile-change
 endif
+endif
 
 $(PROJECT).d::
 	$(verbose) :

test/core_deps.mk

@@ -825,6 +825,75 @@ dep_shelldep = git file://$(abspath $(APP)_shelldep) master\
 	$t cmp $(APP)/expected-all-deps.txt $(APP)/.erlang.mk/recursive-deps-list.log
 	$t $(MAKE) -C $(APP) --no-print-directory distclean $v
 
+core-deps-makefile-change: init
+
+	$i "Bootstrap a new OTP application named $(APP)"
+	$t mkdir $(APP)/
+	$t cp ../erlang.mk $(APP)/
+	$t $(MAKE) -C $(APP) -f erlang.mk bootstrap $v
+
+	$i "Build the application"
+	$t $(MAKE) -C $(APP) $v
+
+	$i "Add Cowlib to the list of dependencies"
+	$t perl -ni.bak -e 'print;if ($$.==1) {print "DEPS = cowlib\n"}' $(APP)/Makefile
+
+ifdef LEGACY
+	$i "Add Cowlib to the applications key in the .app.src file"
+	$t perl -ni.bak -e 'print;if ($$.==7) {print "\t\tcowlib,\n"}' $(APP)/src/$(APP).app.src
+endif
+
+	$i "Build the application again"
+	$t $(MAKE) -C $(APP) $v
+
+	$i "Check that Cowlib was included in the .app file"
+	$t $(ERL) -pa $(APP)/ebin/ -eval " \
+		ok = application:load($(APP)), \
+		{ok, Apps} = application:get_key($(APP), applications), \
+		true = lists:member(cowlib, Apps), \
+		halt()."
+
+core-deps-dep-makefile-change: init
+
+	$i "Bootstrap a new OTP application named $(APP)"
+	$t mkdir $(APP)/
+	$t cp ../erlang.mk $(APP)/
+	$t $(MAKE) -C $(APP) -f erlang.mk bootstrap $v
+
+	$i "Bootstrap a new OTP library named my_dep inside $(APP)"
+	$t mkdir $(APP)/my_dep
+	$t cp ../erlang.mk $(APP)/my_dep/
+	$t $(MAKE) -C $(APP)/my_dep/ -f erlang.mk bootstrap-lib $v
+
+	$i "Add my_dep to the list of dependencies"
+	$t perl -ni.bak -e 'print;if ($$.==1) {print "DEPS = my_dep\ndep_my_dep = ln $(CURDIR)/$(APP)/my_dep/\n"}' $(APP)/Makefile
+
+ifdef LEGACY
+	$i "Add my_dep to the applications key in the .app.src file"
+	$t perl -ni.bak -e 'print;if ($$.==7) {print "\t\tmy_dep,\n"}' $(APP)/src/$(APP).app.src
+endif
+
+	$i "Build the application"
+	$t $(MAKE) -C $(APP) NO_AUTOPATCH=my_dep $v
+
+	$i "Add Cowlib to the list of dependencies in my_dep"
+	$t perl -ni.bak -e 'print;if ($$.==1) {print "DEPS = cowlib\n"}' $(APP)/my_dep/Makefile
+
+ifdef LEGACY
+	$i "Add Cowlib to the applications key in my_dep's .app.src file"
+	$t perl -ni.bak -e 'print;if ($$.==7) {print "\t\tcowlib,\n"}' $(APP)/my_dep/src/my_dep.app.src
+endif
+
+	$i "Build the application again"
+	$t $(MAKE) -C $(APP) $v
+
+	$i "Check that Cowlib was included in my_dep's .app file"
+	$t $(ERL) -pa $(APP)/my_dep/ebin/ -eval " \
+		ok = application:load(my_dep), \
+		{ok, Apps} = application:get_key(my_dep, applications), \
+		true = lists:member(cowlib, Apps), \
+		halt()."
+
 core-deps-mv: init
 
 	$i "Bootstrap a new OTP library named $(APP)"