make: add targets to debug dependencies variables

Add a 'dependency_debug' and a 'DEPENDENCY_DEBUG=1' option for
'info-boards-supported' to save some variables used when resolving
dependencies.

This should help tracking changes introduced when refactoring the
dependency parsing.

Makefile.include

@@ -110,6 +110,9 @@ include $(RIOTMAKE)/info-nproc.inc.mk
 # List of boards variables
 include $(RIOTMAKE)/boards.inc.mk
 
+# Debug targets for build system migration
+include $(RIOTMAKE)/dependencies_debug.inc.mk
+
 GLOBAL_GOALS += buildtest buildtest-indocker info-boards-supported info-boards-features-missing info-buildsizes info-buildsizes-diff
 ifneq (, $(filter $(GLOBAL_GOALS), $(MAKECMDGOALS)))
   BOARD=none

makefiles/dependencies_debug.inc.mk

@@ -0,0 +1,42 @@
+# Debug targets to evaluate dependency migrations
+#
+# The goal is to get the value of variables used for dependency resolution
+# and the impact of refactoring
+
+# Files output can be generated through `info-boards-supported` evaluation with
+#
+#     DEPENDENCY_DEBUG=1 make info-boards-supported
+#
+# And for each board in the normal make context with
+#
+#     BOARD=board_name make dependency_debug
+#
+# To compare in an aggregated file, you can run in an application directory:
+#
+#    for board in $(make info-boards); do DEPENDENCY_DEBUG_OUTPUT_DIR=bin/info BOARD=${board} make dependency_debug; done; cat bin/info/* > bin/deps_info
+#    DEPENDENCY_DEBUG=1 DEPENDENCY_DEBUG_OUTPUT_DIR=bin/info-global make info-boards-supported; cat bin/info-global/* > bin/deps_info-boards-supported
+#    # And compare both files
+#    diff -u bin/deps_info bin/deps_info-boards-supported
+#
+# And when comparing two revisions, include the revision in the file names
+
+.PHONY: dependency_debug
+dependency_debug:
+	$(call file_save_dependencies_variables,dependencies_info)
+	@:
+
+DEPENDENCY_DEBUG_OUTPUT_DIR ?= $(CURDIR)
+
+# Save variables that are used for parsing dependencies
+_DEPS_DEBUG_VARS += BOARD CPU CPU_MODEL CPU_FAM
+_DEPS_DEBUG_VARS += FEATURES_PROVIDED FEATURES_REQUIRED FEATURES_OPTIONAL FEATURES_USED FEATURES_MISSING FEATURES_CONFLICT FEATURES_CONFLICTING
+_DEPS_DEBUG_VARS += USEMODULE DEFAULT_MODULE DISABLE_MODULE
+DEPS_DEBUG_VARS ?= $(_DEPS_DEBUG_VARS)
+
+# Put some dummy first line to be sure the file is create from scratch
+file_save_dependencies_variables = $(call file_save_variable,$(DEPENDENCY_DEBUG_OUTPUT_DIR)/$1_$(BOARD),$(DEPS_DEBUG_VARS))
+file_save_variable = $(shell mkdir -p $(dir $1); rm -f $1)$(foreach v,$2,$(file >>$1,$(call _print_var,$v)))
+
+# Remove spaces in case of empty value
+# Remove spaces around value as it happens
+_print_var = $(strip $1 = $(strip $($1)))

makefiles/info-global.inc.mk

@@ -31,6 +31,10 @@ define board_missing_features
     BOARDS_FEATURES_MISSING += "$(1) $$(FEATURES_MISSING)"
     BOARDS_WITH_MISSING_FEATURES += $(1)
   endif
+
+  ifneq (,$$(DEPENDENCY_DEBUG))
+    $$(call file_save_dependencies_variables,dependencies_info-boards-supported)
+  endif
 endef
 
 BOARDS := $(filter $(if $(BOARD_WHITELIST), $(BOARD_WHITELIST), %), $(BOARDS))