Add 'generate-appups' command

To further support OTP releases I have added support for generating
application appup files. These include instructions that systools uses
to generate a relup file which contains the low level instructions
needed to perform a hot code upgrade. My goal with this module is to
produce "good enough" appup files or at least a skeleton to help one get
started with something more complex. If an appup file already exists for
an application this command will not attempt to create a new one.

Usage:
$ rebar generate-appups previous_release=/path/to/old/version

Generally this command will be run just before 'generate-upgrade'.

ebin/rebar.app

@@ -3,6 +3,7 @@
   {vsn, "2"},
   {modules, [ rebar,
               rebar_abnfc_compiler,
+              rebar_appups,
               rebar_app_utils,
               rebar_base_compiler,
               rebar_config,
@@ -80,6 +81,7 @@
                               ]},
 
                     {rel_dir, [
+                               rebar_appups,
                                rebar_reltool,
                                rebar_upgrade
                               ]}

src/rebar.erl

@@ -224,6 +224,8 @@ generate    [dump_spec=0/1]          Build release with reltool
 
 generate-upgrade  previous_release=path  Build an upgrade package
 
+generate-appups   previous_release=path Generate appup files
+
 eunit       [suite=foo]              Run eunit [test/foo_tests.erl] tests
 ct          [suite=] [case=]         Run common_test suites in ./test
 
@@ -277,8 +279,8 @@ filter_flags([Item | Rest], Commands) ->
 command_names() ->
     ["build-plt", "check-deps", "check-plt", "clean", "compile", "create",
      "create-app", "create-node", "ct", "delete-deps", "dialyze", "doc",
-     "eunit", "generate", "generate-upgrade", "get-deps", "help",
+     "eunit", "generate", "generate-appups", "generate-upgrade", "get-deps",
-     "list-templates", "update-deps", "version", "xref"].
+     "help", "list-templates", "update-deps", "version", "xref"].
 
 unabbreviate_command_names([]) ->
     [];

src/rebar_appups.erl

@@ -0,0 +1,185 @@
+%% -*- erlang-indent-level: 4;indent-tabs-mode: nil -*-
+%% ex: ts=4 sw=4 et
+%% -------------------------------------------------------------------
+%%
+%% rebar: Erlang Build Tools
+%%
+%% Copyright (c) 2011 Joe Williams (joe@joetify.com)
+%%
+%% Permission is hereby granted, free of charge, to any person obtaining a copy
+%% of this software and associated documentation files (the "Software"), to deal
+%% in the Software without restriction, including without limitation the rights
+%% to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+%% copies of the Software, and to permit persons to whom the Software is
+%% furnished to do so, subject to the following conditions:
+%%
+%% The above copyright notice and this permission notice shall be included in
+%% all copies or substantial portions of the Software.
+%%
+%% THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+%% IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+%% FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+%% AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+%% LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+%% OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+%% THE SOFTWARE.
+%% ------------------------------------------------------------------
+
+-module(rebar_appups).
+
+-include("rebar.hrl").
+
+-export(['generate-appups'/2]).
+
+-define(APPUPFILEFORMAT, "%% appup generated for ~p by rebar (~p)~n"
+        "{~p, [{~p, ~p}], [{~p, []}]}.~n").
+
+%% ====================================================================
+%% Public API
+%% ====================================================================
+
+'generate-appups'(_Config, ReltoolFile) ->
+    %% Get the old release path
+    OldVerPath = rebar_utils:get_previous_release_path(),
+
+    %% Get the new and old release name and versions
+    {Name, _Ver} = rebar_utils:get_reltool_release_info(ReltoolFile),
+    NewVerPath = filename:join([".", Name]),
+    {NewName, NewVer} = rebar_utils:get_rel_release_info(Name, NewVerPath),
+    {OldName, OldVer} = rebar_utils:get_rel_release_info(Name, OldVerPath),
+
+    %% Run some simple checks
+    true = rebar_utils:prop_check(NewVer =/= OldVer,
+                                  "New and old .rel versions match~n", []),
+    true = rebar_utils:prop_check(
+             NewName == OldName,
+             "Reltool and .rel release names do not match~n", []),
+
+    %% Get lists of the old and new app files
+    OldAppFiles = rebar_utils:find_files(
+                    filename:join([OldVerPath, "lib"]), "^.*.app$"),
+    NewAppFiles = rebar_utils:find_files(
+                    filename:join([NewName, "lib"]), "^.*.app$"),
+
+    %% Find all the apps that have been upgraded
+    UpgradedApps = get_upgraded_apps(OldAppFiles, NewAppFiles),
+
+    %% Get a list of any appup files that exist in the new release
+    NewAppUpFiles = rebar_utils:find_files(
+                      filename:join([NewName, "lib"]), "^.*.appup$"),
+
+    %% Convert the list of appup files into app names
+    AppUpApps = lists:map(fun(File) ->
+                                  file_to_name(File)
+                          end, NewAppUpFiles),
+
+    %% Create a list of apps that don't already have appups
+    Apps = genappup_which_apps(UpgradedApps, AppUpApps),
+
+    %% Generate appup files
+    generate_appup_files(Name, OldVerPath, Apps),
+
+    ok.
+
+%% ===================================================================
+%% Internal functions
+%% ===================================================================
+
+get_upgraded_apps(OldAppFiles, NewAppFiles) ->
+    OldAppsVer = [get_app_version(AppFile) || AppFile <- OldAppFiles],
+    NewAppsVer = [get_app_version(AppFile) || AppFile <- NewAppFiles],
+    UpgradedApps = lists:subtract(NewAppsVer, OldAppsVer),
+    lists:map(
+      fun({App, NewVer}) ->
+              {App, OldVer} = proplists:lookup(App, OldAppsVer),
+              {App, {OldVer, NewVer}}
+      end,
+      UpgradedApps).
+
+get_app_version(File) ->
+    case file:consult(File) of
+        {ok,[{application, Name,[_,{vsn,Ver}|_]}]} ->
+            {Name, Ver};
+        _ ->
+            ?ABORT("Failed to parse ~s~n", [File])
+    end.
+
+file_to_name(File) ->
+    filename:rootname(filename:basename(File)).
+
+genappup_which_apps(UpgradedApps, [First|Rest]) ->
+    List = proplists:delete(First, UpgradedApps),
+    genappup_which_apps(List, Rest);
+genappup_which_apps(Apps, []) ->
+    Apps.
+
+generate_appup_files(Name, OldVerPath, [{App, {OldVer, NewVer}}|Rest]) ->
+    OldEbinDir = filename:join([".", OldVerPath, "lib",
+                                atom_to_list(App) ++ "-" ++ OldVer, "ebin"]),
+    NewEbinDir = filename:join([".", Name, "lib",
+                                atom_to_list(App) ++ "-" ++ NewVer, "ebin"]),
+
+    {AddedFiles, DeletedFiles, ChangedFiles} = beam_lib:cmp_dirs(NewEbinDir,
+                                                                 OldEbinDir),
+
+    Added = [generate_instruction(added, File) || File <- AddedFiles],
+    Deleted = [generate_instruction(deleted, File) || File <- DeletedFiles],
+    Changed = [generate_instruction(changed, File) || File <- ChangedFiles],
+
+    Inst = lists:append([Added, Deleted, Changed]),
+
+    AppUpFile = filename:join([NewEbinDir, atom_to_list(App) ++ ".appup"]),
+
+    ok = file:write_file(AppUpFile,
+                         io_lib:fwrite(?APPUPFILEFORMAT,
+                                       [App, rebar_utils:now_str(), NewVer,
+                                        OldVer, Inst, OldVer])),
+
+    ?CONSOLE("Generated appup for ~p~n", [App]),
+    generate_appup_files(Name, OldVerPath, Rest);
+generate_appup_files(_, _, []) ->
+    ?CONSOLE("Appup generation complete~n", []).
+
+generate_instruction(added, File) ->
+    Name = list_to_atom(file_to_name(File)),
+    {add_module, Name};
+generate_instruction(deleted, File) ->
+    Name = list_to_atom(file_to_name(File)),
+    {delete_module, Name};
+generate_instruction(changed, {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).
+
+generate_instruction_advanced(Name, undefined, undefined) ->
+    %% Not a behavior or code change, assume purely functional
+    {load_module, Name};
+generate_instruction_advanced(Name, [supervisor], _) ->
+    %% Supervisor
+    {update, Name, supervisor};
+generate_instruction_advanced(Name, _, code_change) ->
+    %% Includes code_change export
+    {update, Name, {advanced, []}};
+generate_instruction_advanced(Name, _, _) ->
+    %% Anything else
+    {update, Name}.
+
+get_behavior(List) ->
+    Attributes = proplists:get_value(attributes, List),
+    Behavior = case proplists:get_value(behavior, Attributes) of
+                   undefined ->
+                       proplists:get_value(behaviour, Attributes);
+                   Else ->
+                       Else
+               end,
+    Behavior.
+
+is_code_change(List) ->
+    Exports = proplists:get_value(exports, List),
+    case proplists:is_defined(code_change, Exports) of
+        true ->
+            code_change;
+        false ->
+            undefined
+    end.

src/rebar_utils.erl

@@ -37,7 +37,11 @@
          erl_to_mod/1,
          abort/2,
          escript_foldl/3,
-         find_executable/1]).
+         find_executable/1,
+         get_reltool_release_info/1,
+         get_rel_release_info/2,
+         get_previous_release_path/0,
+         prop_check/3]).
 
 -include("rebar.hrl").
 
@@ -151,6 +155,42 @@ find_executable(Name) ->
             "\"" ++ filename:nativename(Path) ++ "\""
     end.
 
+%% Get release name and version from a reltool.config
+get_reltool_release_info(ReltoolFile) ->
+    %% expect sys to be the first proplist in reltool.config
+    case file:consult(ReltoolFile) of
+        {ok, [{sys, Config}| _]} ->
+            %% expect the first rel in the proplist to be the one you want
+            {rel, Name, Ver, _} = proplists:lookup(rel, Config),
+            {Name, Ver};
+        _ ->
+            ?ABORT("Failed to parse ~s~n", [ReltoolFile])
+    end.
+
+%% Get release name and version from a rel file
+get_rel_release_info(Name, Path) ->
+    [RelFile] = filelib:wildcard(filename:join([Path, "releases", "*",
+                                                Name ++ ".rel"])),
+    [BinDir|_] = re:replace(RelFile, Name ++ "\\.rel", ""),
+    {ok, [{release, {Name1, Ver}, _, _}]} =
+        file:consult(filename:join([binary_to_list(BinDir),
+                                    Name ++ ".rel"])),
+    {Name1, Ver}.
+
+%% Get the previous release path from a global variable
+get_previous_release_path() ->
+    case rebar_config:get_global(previous_release, false) of
+        false ->
+            ?ABORT("previous_release=PATH is required to "
+                   "create upgrade package~n", []);
+        OldVerPath ->
+            OldVerPath
+    end.
+
+%% Helper function for checking values and aborting when needed
+prop_check(true, _, _) -> true;
+prop_check(false, Msg, Args) -> ?ABORT(Msg, Args).
+
 %% ====================================================================
 %% Internal functions
 %% ====================================================================

test/upgrade_project/README.md

@@ -21,6 +21,7 @@
 
     rebar compile
     rebar generate
+    rebar generate-appups previous_release=dummy_0.1
     rebar generate-upgrade previous_release=dummy_0.1
     tar -zvtf rel/dummy_0.2.tar.gz
 

test/upgrade_project/apps/dummy/ebin/dummy.appup

@@ -1,8 +0,0 @@
-{"0.2",
-    [{"0.1",[
-                {update, dummy_server, {advanced, [foo]}}
-            ]}],
-    [{"0.1",[
-                {update, dummy_server, {advanced, [foo]}}
-            ]}]
-}.