From ebbb927cbc5ea634dc5af02803a0a271d3312f82 Mon Sep 17 00:00:00 2001
From: Robert Newson <robert.newson@cloudant.com>
Date: Thu, 19 Sep 2013 15:45:55 +0100
Subject: [PATCH] Allow specification of module dependencies for appups

The order in which modules, within an application, are loaded can be
important. This patch adds allows the specification of module
dependencies such that generate .appup/.relup scripts will load a
module's dependent modules before itself.

To use:

in rebar.config, add a module_deps

{module_deps, [{ModuleName, [DependentModuleName, ...]}]}.

ModuleName is the name of any module, followed by a list of module
names that it depends on.
---
 src/rebar_appups.erl | 43 ++++++++++++++++++++++++++-----------------
 1 file changed, 26 insertions(+), 17 deletions(-)

diff --git a/src/rebar_appups.erl b/src/rebar_appups.erl
index 722f161..a51c30d 100644
--- a/src/rebar_appups.erl
+++ b/src/rebar_appups.erl
@@ -50,6 +50,8 @@
     PrevRelPath = rebar_rel_utils:get_previous_release_path(Config),
     OldVerPath = filename:join([TargetParentDir, PrevRelPath]),
 
+    ModDeps = rebar_config:get(Config, module_deps, []),
+
     %% Get the new and old release name and versions
     {Name, _Ver} = rebar_rel_utils:get_reltool_release_info(ReltoolConfig),
     NewVerPath = filename:join([TargetParentDir, Name]),
@@ -77,7 +79,7 @@
     UpgradeApps = genappup_which_apps(Upgraded, AppUpApps),
 
     %% Generate appup files for upgraded apps
-    generate_appup_files(NewVerPath, OldVerPath, UpgradeApps),
+    generate_appup_files(NewVerPath, OldVerPath, ModDeps, UpgradeApps),
 
     {ok, Config1}.
 
@@ -139,9 +141,9 @@ genappup_which_apps(UpgradedApps, [First|Rest]) ->
 genappup_which_apps(Apps, []) ->
     Apps.
 
-generate_appup_files(NewVerPath, OldVerPath, [{_App, {undefined, _}}|Rest]) ->
-    generate_appup_files(NewVerPath, OldVerPath, Rest);
-generate_appup_files(NewVerPath, OldVerPath, [{App, {OldVer, NewVer}}|Rest]) ->
+generate_appup_files(NewVerPath, OldVerPath, ModDeps, [{_App, {undefined, _}}|Rest]) ->
+    generate_appup_files(NewVerPath, OldVerPath, ModDeps, Rest);
+generate_appup_files(NewVerPath, OldVerPath, ModDeps, [{App, {OldVer, NewVer}}|Rest]) ->
     OldEbinDir = filename:join([OldVerPath, "lib",
                                 atom_to_list(App) ++ "-" ++ OldVer, "ebin"]),
     NewEbinDir = filename:join([NewVerPath, "lib",
@@ -150,9 +152,14 @@ generate_appup_files(NewVerPath, OldVerPath, [{App, {OldVer, NewVer}}|Rest]) ->
     {AddedFiles, DeletedFiles, ChangedFiles} = beam_lib:cmp_dirs(NewEbinDir,
                                                                  OldEbinDir),
 
+    ChangedNames = [list_to_atom(file_to_name(F)) || {F, _} <- ChangedFiles],
+    ModDeps1 = [{N, [M1 || M1 <- M, lists:member(M1, ChangedNames)]}
+                || {N, M} <- ModDeps],
+
     Added = [generate_instruction(added, File) || File <- AddedFiles],
     Deleted = [generate_instruction(deleted, File) || File <- DeletedFiles],
-    Changed = [generate_instruction(changed, File) || File <- ChangedFiles],
+    Changed = [generate_instruction(changed, ModDeps1, File)
+               || File <- ChangedFiles],
 
     Inst = lists:append([Added, Deleted, Changed]),
 
@@ -164,8 +171,8 @@ generate_appup_files(NewVerPath, OldVerPath, [{App, {OldVer, NewVer}}|Rest]) ->
                                         OldVer, Inst, OldVer])),
 
     ?CONSOLE("Generated appup for ~p~n", [App]),
-    generate_appup_files(NewVerPath, OldVerPath, Rest);
-generate_appup_files(_, _, []) ->
+    generate_appup_files(NewVerPath, OldVerPath, ModDeps, Rest);
+generate_appup_files(_, _, _, []) ->
     ?CONSOLE("Appup generation complete~n", []).
 
 generate_instruction(added, File) ->
@@ -173,25 +180,27 @@ generate_instruction(added, File) ->
     {add_module, Name};
 generate_instruction(deleted, File) ->
     Name = list_to_atom(file_to_name(File)),
-    {delete_module, Name};
-generate_instruction(changed, {File, _}) ->
+    {delete_module, Name}.
+
+generate_instruction(changed, ModDeps, {File, _}) ->
     {ok, {Name, List}} = beam_lib:chunks(File, [attributes, exports]),
     Behavior = get_behavior(List),
     CodeChange = is_code_change(List),
-    generate_instruction_advanced(Name, Behavior, CodeChange).
+    Deps = proplists:get_value(Name, ModDeps, []),
+    generate_instruction_advanced(Name, Behavior, CodeChange, Deps).
 
-generate_instruction_advanced(Name, undefined, undefined) ->
+generate_instruction_advanced(Name, undefined, undefined, Deps) ->
     %% Not a behavior or code change, assume purely functional
-    {load_module, Name};
-generate_instruction_advanced(Name, [supervisor], _) ->
+    {load_module, Name, Deps};
+generate_instruction_advanced(Name, [supervisor], _, _) ->
     %% Supervisor
     {update, Name, supervisor};
-generate_instruction_advanced(Name, _, code_change) ->
+generate_instruction_advanced(Name, _, code_change, Deps) ->
     %% Includes code_change export
-    {update, Name, {advanced, []}};
-generate_instruction_advanced(Name, _, _) ->
+    {update, Name, {advanced, []}, Deps};
+generate_instruction_advanced(Name, _, _, Deps) ->
     %% Anything else
-    {load_module, Name}.
+    {load_module, Name, Deps}.
 
 get_behavior(List) ->
     Attributes = proplists:get_value(attributes, List),