Add "necessary evil" autopatch feature

The point of this feature is to fix common issues users
experience.

This feature, when used, attempts to fix projects that
are incompatible with erlang.mk. It currently is able
to build a new Makefile based on information it finds
in a rebar.config file (only deps for now) and also
to fix the .app.src file in various ways.

3 files changed, 112 insertions, 0 deletions

diff --git a/README.md b/README.md
index d9717f6..c182429 100644
--- a/README.md
+++ b/README.md
@@ -138,6 +138,24 @@ dep_ct_helper = git https://github.com/extend/ct_helper.git master
 Please note that the test dependencies will only be compiled once
 when they are fetched, unlike the normal dependencies.
 
+Autopatch
+---------
+
+The autopatch features allows you to automatically fix packages
+that are not compatible with erlang.mk. It can also be used to
+convert compatible packages to use erlang.mk itself for building
+when used as dependency.
+
+The patching occurs only once, immediately after the package has
+been fetched.
+
+erlang.mk defines a number of packages to be patched. You can add
+more packages to the list by appending the `AUTOPATCH` variable.
+
+``` Makefile
+AUTOPATCH += gproc
+```
+
 Releases
 --------
 
diff --git a/core/deps.mk b/core/deps.mk
index 7d4b974..35fefb5 100644
--- a/core/deps.mk
+++ b/core/deps.mk
@@ -5,6 +5,9 @@
 
 # Configuration.
 
+AUTOPATCH ?= edown gen_leader gproc
+export AUTOPATCH
+
 DEPS_DIR ?= $(CURDIR)/deps
 export DEPS_DIR
 
@@ -42,6 +45,41 @@ distclean:: distclean-deps distclean-pkg
 
 # Deps related targets.
 
+define dep_autopatch
+	$(ERL) -eval " \
+DepDir = \"$(DEPS_DIR)/$(1)/\", \
+fun() -> \
+	{ok, Conf} = file:consult(DepDir ++ \"rebar.config\"), \
+	File = case lists:keyfind(deps, 1, Conf) of false -> []; {_, Deps} -> \
+		[begin {Method, Repo, Commit} = case Repos of \
+			{git, R} -> {git, R, master}; \
+			{M, R, {branch, C}} -> {M, R, C}; \
+			{M, R, {tag, C}} -> {M, R, C}; \
+			{M, R, C} -> {M, R, C} \
+		end, \
+		io_lib:format(\"DEPS += ~s\ndep_~s = ~s ~s ~s~n\", [Name, Name, Method, Repo, Commit]) \
+		end || {Name, _, Repos} <- Deps] \
+	end, \
+	ok = file:write_file(\"$(DEPS_DIR)/$(1)/Makefile\", [\"ERLC_OPTS = +debug_info\n\n\", File, \"\ninclude erlang.mk\"]) \
+end(), \
+AppSrcOut = \"$(DEPS_DIR)/$(1)/src/$(1).app.src\", \
+AppSrcIn = case filelib:is_regular(AppSrcOut) of false -> \"$(DEPS_DIR)/$(1)/ebin/$(1).app\"; true -> AppSrcOut end, \
+fun() -> \
+	{ok, [{application, $(1), L}]} = file:consult(AppSrcIn), \
+	L2 = case lists:keyfind(modules, 1, L) of {_, _} -> L; false -> [{modules, []}|L] end, \
+	L3 = case lists:keyfind(vsn, 1, L2) of {vsn, git} -> lists:keyreplace(vsn, 1, L2, {vsn, \"git\"}); _ -> L2 end, \
+	ok = file:write_file(AppSrcOut, io_lib:format(\"~p.~n\", [{application, $(1), L3}])) \
+end(), \
+case AppSrcOut of AppSrcIn -> ok; _ -> ok = file:delete(AppSrcIn) end, \
+halt()."
+endef
+
+ifeq ($(V),0)
+define dep_autopatch_verbose
+	@echo " PATCH " $(1);
+endef
+endif
+
 define dep_fetch
 	if [ "$$$$VS" = "git" ]; then \
 		git clone -n -- $$$$REPO $(DEPS_DIR)/$(1); \
@@ -73,6 +111,15 @@ else
 	COMMIT=$(word 3,$(dep_$(1))); \
 	$(call dep_fetch,$(1))
 endif
+ifneq ($(filter $(1),$(AUTOPATCH)),)
+	$(call dep_autopatch_verbose,$(1)) if [ -f $(DEPS_DIR)/$(1)/rebar.config ]; then \
+		$(call dep_autopatch,$(1)); \
+		cd $(DEPS_DIR)/$(1)/ && ln -s ../../erlang.mk; \
+	elif [ ! -f $(DEPS_DIR)/$(1)/Makefile ]; then \
+		echo "ERLC_OPTS = +debug_info\ninclude erlang.mk" > $(DEPS_DIR)/$(1)/Makefile; \
+		cd $(DEPS_DIR)/$(1)/ && ln -s ../../erlang.mk; \
+	fi
+endif
 endef
 
 $(foreach dep,$(DEPS),$(eval $(call dep_target,$(dep))))
diff --git a/erlang.mk b/erlang.mk
index b943618..e7afbb8 100644
--- a/erlang.mk
+++ b/erlang.mk
@@ -110,6 +110,9 @@ erlang-mk:
 
 # Configuration.
 
+AUTOPATCH ?= edown gen_leader gproc
+export AUTOPATCH
+
 DEPS_DIR ?= $(CURDIR)/deps
 export DEPS_DIR
 
@@ -147,6 +150,41 @@ distclean:: distclean-deps distclean-pkg
 
 # Deps related targets.
 
+define dep_autopatch
+	$(ERL) -eval " \
+DepDir = \"$(DEPS_DIR)/$(1)/\", \
+fun() -> \
+	{ok, Conf} = file:consult(DepDir ++ \"rebar.config\"), \
+	File = case lists:keyfind(deps, 1, Conf) of false -> []; {_, Deps} -> \
+		[begin {Method, Repo, Commit} = case Repos of \
+			{git, R} -> {git, R, master}; \
+			{M, R, {branch, C}} -> {M, R, C}; \
+			{M, R, {tag, C}} -> {M, R, C}; \
+			{M, R, C} -> {M, R, C} \
+		end, \
+		io_lib:format(\"DEPS += ~s\ndep_~s = ~s ~s ~s~n\", [Name, Name, Method, Repo, Commit]) \
+		end || {Name, _, Repos} <- Deps] \
+	end, \
+	ok = file:write_file(\"$(DEPS_DIR)/$(1)/Makefile\", [\"ERLC_OPTS = +debug_info\n\n\", File, \"\ninclude erlang.mk\"]) \
+end(), \
+AppSrcOut = \"$(DEPS_DIR)/$(1)/src/$(1).app.src\", \
+AppSrcIn = case filelib:is_regular(AppSrcOut) of false -> \"$(DEPS_DIR)/$(1)/ebin/$(1).app\"; true -> AppSrcOut end, \
+fun() -> \
+	{ok, [{application, $(1), L}]} = file:consult(AppSrcIn), \
+	L2 = case lists:keyfind(modules, 1, L) of {_, _} -> L; false -> [{modules, []}|L] end, \
+	L3 = case lists:keyfind(vsn, 1, L2) of {vsn, git} -> lists:keyreplace(vsn, 1, L2, {vsn, \"git\"}); _ -> L2 end, \
+	ok = file:write_file(AppSrcOut, io_lib:format(\"~p.~n\", [{application, $(1), L3}])) \
+end(), \
+case AppSrcOut of AppSrcIn -> ok; _ -> ok = file:delete(AppSrcIn) end, \
+halt()."
+endef
+
+ifeq ($(V),0)
+define dep_autopatch_verbose
+	@echo " PATCH " $(1);
+endef
+endif
+
 define dep_fetch
 	if [ "$$$$VS" = "git" ]; then \
 		git clone -n -- $$$$REPO $(DEPS_DIR)/$(1); \
@@ -178,6 +216,15 @@ else
 	COMMIT=$(word 3,$(dep_$(1))); \
 	$(call dep_fetch,$(1))
 endif
+ifneq ($(filter $(1),$(AUTOPATCH)),)
+	$(call dep_autopatch_verbose,$(1)) if [ -f $(DEPS_DIR)/$(1)/rebar.config ]; then \
+		$(call dep_autopatch,$(1)); \
+		cd $(DEPS_DIR)/$(1)/ && ln -s ../../erlang.mk; \
+	elif [ ! -f $(DEPS_DIR)/$(1)/Makefile ]; then \
+		echo "ERLC_OPTS = +debug_info\ninclude erlang.mk" > $(DEPS_DIR)/$(1)/Makefile; \
+		cd $(DEPS_DIR)/$(1)/ && ln -s ../../erlang.mk; \
+	fi
+endif
 endef
 
 $(foreach dep,$(DEPS),$(eval $(call dep_target,$(dep))))