From 0932920d3612a259c8f66710cb16bccfb1da32e9 Mon Sep 17 00:00:00 2001
From: Thales Macedo Garitezi <thalesmg@gmail.com>
Date: Thu, 25 Nov 2021 15:02:18 -0300
Subject: [PATCH] chore(appup): make update_appup.escript output only
 differences for external dependencies

Currently, the update_appup.escript outputs as an error the full appup
file for external dependencies, even if all the changes are already
contained in the depency.  Here, we make it only output the missing
actions to be inserted, to aid in seeing what are the differences.
---
 scripts/update_appup.escript | 77 ++++++++++++++++++++++++++++++++----
 1 file changed, 69 insertions(+), 8 deletions(-)

diff --git a/scripts/update_appup.escript b/scripts/update_appup.escript
index 9fc8f618e..1de4ab899 100755
--- a/scripts/update_appup.escript
+++ b/scripts/update_appup.escript
@@ -99,8 +99,31 @@ main(Options, Baseline) ->
                 [] ->
                     ok;
                 _ ->
-                    set_invalid(),
-                    log("ERROR: The appup files are incomplete. Missing changes:~n   ~p", [AppupChanges])
+                    Diffs =
+                        lists:filtermap(
+                          fun({App, {Upgrade, Downgrade, OldUpgrade, OldDowngrade}}) ->
+                                  DiffUp = diff_appup_instructions(Upgrade, OldUpgrade),
+                                  DiffDown = diff_appup_instructions(Downgrade, OldDowngrade),
+                                  case {DiffUp, DiffDown} of
+                                      {[], []} ->
+                                          %% no diff for external dependency
+                                          false;
+                                      _ ->
+                                          Diffs = #{ up => DiffUp
+                                                   , down => DiffDown
+                                                   },
+                                          {true, {App, Diffs}}
+                                  end
+                          end,
+                          AppupChanges),
+                    case Diffs =:= [] of
+                        true ->
+                            ok;
+                        false ->
+                            set_invalid(),
+                            log("ERROR: The appup files are incomplete. Missing changes:~n   ~p",
+                                [Diffs])
+                    end
             end;
         false ->
             update_appups(AppupChanges)
@@ -189,9 +212,35 @@ find_appup_actions(App, CurrAppIdx, PrevAppIdx = #app{version = PrevVersion}) ->
             %% The appup file has been already updated:
             [];
        true ->
-            [{App, {Upgrade, Downgrade}}]
+            [{App, {Upgrade, Downgrade, OldUpgrade, OldDowngrade}}]
     end.
 
+%% For external dependencies, show only the changes that are missing
+%% in their current appup.
+diff_appup_instructions(ComputedChanges, PresentChanges) ->
+    lists:foldr(
+      fun({Vsn, ComputedActions}, Acc) ->
+              case find_matching_version(Vsn, PresentChanges) of
+                  undefined ->
+                      [{Vsn, ComputedActions} | Acc];
+                  PresentActions ->
+                      DiffActions = ComputedActions -- PresentActions,
+                      case DiffActions of
+                          [] ->
+                              %% no diff
+                              Acc;
+                          _ ->
+                              [{Vsn, DiffActions} | Acc]
+                      end
+              end
+      end,
+      [],
+      ComputedChanges).
+
+%% TODO: handle regexes
+find_matching_version(Vsn, PresentChanges) ->
+    proplists:get_value(Vsn, PresentChanges).
+
 find_old_appup_actions(App, PrevVersion) ->
     {Upgrade0, Downgrade0} =
         case locate(ebin_current, App, ".appup") of
@@ -270,12 +319,12 @@ check_appup_files() ->
 
 update_appups(Changes) ->
     lists:foreach(
-      fun({App, {Upgrade, Downgrade}}) ->
-              do_update_appup(App, Upgrade, Downgrade)
+      fun({App, {Upgrade, Downgrade, OldUpgrade, OldDowngrade}}) ->
+              do_update_appup(App, Upgrade, Downgrade, OldUpgrade, OldDowngrade)
       end,
       Changes).
 
-do_update_appup(App, Upgrade, Downgrade) ->
+do_update_appup(App, Upgrade, Downgrade, OldUpgrade, OldDowngrade) ->
     case locate(src, App, ".appup.src") of
         {ok, AppupFile} ->
             render_appfile(AppupFile, Upgrade, Downgrade);
@@ -284,8 +333,20 @@ do_update_appup(App, Upgrade, Downgrade) ->
                 {ok, AppupFile} ->
                     render_appfile(AppupFile, Upgrade, Downgrade);
                 false ->
-                    set_invalid(),
-                    log("ERROR: Appup file for the external dependency '~p' is not complete.~n       Missing changes: ~p~n", [App, Upgrade])
+                    DiffUp = diff_appup_instructions(Upgrade, OldUpgrade),
+                    DiffDown = diff_appup_instructions(Downgrade, OldDowngrade),
+                    case {DiffUp, DiffDown} of
+                        {[], []} ->
+                            %% no diff for external dependency; ignore
+                            ok;
+                        _ ->
+                            set_invalid(),
+                            Diffs = #{ up => DiffUp
+                                     , down => DiffDown
+                                     },
+                            log("ERROR: Appup file for the external dependency '~p' is not complete.~n       Missing changes: ~100p~n", [App, Diffs]),
+                            log("NOTE: Some changes above might be already covered by regexes.~n")
+                    end
             end
     end.