support single atoms for pkg deps, fetch highest version available

9 files changed, 225 insertions, 170 deletions

diff --git a/src/rebar_app_discover.erl b/src/rebar_app_discover.erl
index 0799313..fe930bd 100644
--- a/src/rebar_app_discover.erl
+++ b/src/rebar_app_discover.erl
@@ -48,9 +48,9 @@ merge_deps(AppInfo, State) ->
     State1 = lists:foldl(fun(Profile, StateAcc) ->
                                  AppProfDeps = rebar_state:get(AppState, {deps, Profile}, []),
                                  TopLevelProfDeps = rebar_state:get(StateAcc, {deps, Profile}, []),
-                                 ProfDeps2 = dedup(lists:keymerge(1,
-                                                                  lists:keysort(1, TopLevelProfDeps),
-                                                                  lists:keysort(1, AppProfDeps))),
+                                 ProfDeps2 = dedup(rebar_utils:tup_umerge(
+                                                     rebar_utils:tup_sort(TopLevelProfDeps)
+                                                     ,rebar_utils:tup_sort(AppProfDeps))),
                                  rebar_state:set(StateAcc, {deps, Profile}, ProfDeps2)
                          end, State, lists:reverse(CurrentProfiles)),
 
@@ -164,7 +164,8 @@ create_app_info(AppDir, AppFile) ->
             AppInfo1 = rebar_app_info:applications(
                          rebar_app_info:app_details(AppInfo, AppDetails),
                          IncludedApplications++Applications),
-            rebar_app_info:dir(AppInfo1, AppDir);
+            Valid = rebar_app_utils:validate_application_info(AppInfo1),
+            rebar_app_info:dir(rebar_app_info:valid(AppInfo1, Valid), AppDir);
         _ ->
             error
     end.
diff --git a/src/rebar_config.erl b/src/rebar_config.erl
index c1c4381..97aea91 100644
--- a/src/rebar_config.erl
+++ b/src/rebar_config.erl
@@ -106,21 +106,25 @@ bs(Vars) ->
 
 %% Find deps that have been added to the config after the lock was created
 find_newly_added(ConfigDeps, LockedDeps) ->
-    [Dep || Dep <- ConfigDeps,
-            begin
-                NewDep = ec_cnv:to_binary(element(1, Dep)),
-                case lists:keyfind(NewDep, 1, LockedDeps) of
-                    false ->
-                        true;
-                    Match ->
-                        case element(3, Match) of
-                            0 ->
-                                true;
-                            _ ->
-                                ?WARN("Newly added dep ~s is locked at a lower level. "
-                                     "If you really want to unlock it, use 'rebar3 upgrade ~s'",
-                                     [NewDep, NewDep]),
-                                false
-                        end
-                end
-            end].
+    rebar_utils:filtermap(fun(Dep) when is_tuple(Dep) ->
+                                  check_dep(element(1, Dep), LockedDeps);
+                             (Dep) ->
+                                  check_dep(Dep, LockedDeps)
+                          end, ConfigDeps).
+
+check_dep(Dep, LockedDeps) ->
+    NewDep = ec_cnv:to_binary(Dep),
+    case lists:keyfind(NewDep, 1, LockedDeps) of
+        false ->
+            true;
+        Match ->
+            case element(3, Match) of
+                0 ->
+                    true;
+                _ ->
+                    ?WARN("Newly added dep ~s is locked at a lower level. "
+                         "If you really want to unlock it, use 'rebar3 upgrade ~s'",
+                         [NewDep, NewDep]),
+                    false
+            end
+    end.
diff --git a/src/rebar_digraph.erl b/src/rebar_digraph.erl
index 129ea35..35fd7e7 100644
--- a/src/rebar_digraph.erl
+++ b/src/rebar_digraph.erl
@@ -72,10 +72,12 @@ cull_deps(Graph, Vertices) ->
     cull_deps(Graph,
               Vertices,
               1,
-              lists:foldl(fun({Key, _}, Levels) -> dict:store(Key, 0, Levels) end,
-                          dict:new(), Vertices),
-              lists:foldl(fun({Key, _}=N, Solution) -> dict:store(Key, N, Solution) end,
-                          dict:new(), Vertices),
+              lists:foldl(fun({Key, _}, Levels) ->
+                                  dict:store(Key, 0, Levels)
+                          end, dict:new(), Vertices),
+              lists:foldl(fun({Key, _}=N, Solution) ->
+                                  dict:store(Key, N, Solution)
+                          end, dict:new(), Vertices),
               []).
 
 cull_deps(_Graph, [], _Level, Levels, Solution, Discarded) ->
@@ -99,7 +101,7 @@ cull_deps(Graph, Vertices, Level, Levels, Solution, Discarded) ->
                                                      DiscardedAcc1}
                                             end
                                     end, {NewVertices, SolutionAcc, LevelsAcc, DiscardedAcc}, OutNeighbors)
-                    end, {[], Solution, Levels, Discarded}, lists:keysort(1, Vertices)),
+                    end, {[], Solution, Levels, Discarded}, lists:sort(Vertices)),
     cull_deps(Graph, NV, Level+1, LS, NS, DS).
 
 subgraph(Graph, Vertices) ->
diff --git a/src/rebar_packages.erl b/src/rebar_packages.erl
index 5c67600..3890510 100644
--- a/src/rebar_packages.erl
+++ b/src/rebar_packages.erl
@@ -1,6 +1,8 @@
 -module(rebar_packages).
 
--export([get_packages/1]).
+-export([get_packages/1
+        ,registry/1
+        ,find_highest_matching/3]).
 
 -export_type([package/0]).
 
@@ -37,3 +39,54 @@ get_packages(State) ->
             ?ERROR("Bad packages index, try to fix with `rebar3 update`", []),
             {dict:new(), digraph:new()}
     end.
+
+registry(State) ->
+    Dir = rebar_dir:global_cache_dir(State),
+    RegistryDir = filename:join(Dir, "packages"),
+    HexFile = filename:join(RegistryDir, "registry2"),
+    case ets:file2tab(HexFile) of
+        {ok, T} ->
+            {ok, T};
+        {error, Reason} ->
+            ?DEBUG("Error loading registry: ~p", [Reason]),
+            error
+    end.
+
+
+%% Hex supports use of ~> to specify the version required for a dependency.
+%% Since rebar3 requires exact versions to choose from we find the highest
+%% available version of the dep that passes the constraint.
+
+%% `~>` will never include pre-release versions of its upper bound.
+%% It can also be used to set an upper bound on only the major
+%% version part. See the table below for `~>` requirements and
+%% their corresponding translation.
+%% `~>` | Translation
+%% :------------- | :---------------------
+%% `~> 2.0.0` | `>= 2.0.0 and < 2.1.0`
+%% `~> 2.1.2` | `>= 2.1.2 and < 2.2.0`
+%% `~> 2.1.3-dev` | `>= 2.1.3-dev and < 2.2.0`
+%% `~> 2.0` | `>= 2.0.0 and < 3.0.0`
+%% `~> 2.1` | `>= 2.1.0 and < 3.0.0`
+find_highest_matching(Dep, Constraint, T) ->
+    case ets:lookup(T, Dep) of
+        [{Dep, [[Vsn]]}] ->
+            case ec_semver:pes(Vsn, Constraint) of
+                true ->
+                    Vsn;
+                false ->
+                    ?WARN("Only existing version of ~s is ~s which does not match constraint ~~> ~s. "
+                         "Using anyway, but it is not guarenteed to work.", [Dep, Vsn, Constraint]),
+                    Vsn
+            end;
+        [{Dep, [[HeadVsn | VsnTail]]}] ->
+            lists:foldl(fun(Version, Highest) ->
+                                case ec_semver:pes(Version, Constraint) andalso
+                                    ec_semver:gt(Version, Highest) of
+                                    true ->
+                                        Version;
+                                    false ->
+                                        Highest
+                                end
+                        end, HeadVsn, VsnTail)
+    end.
diff --git a/src/rebar_prv_install_deps.erl b/src/rebar_prv_install_deps.erl
index db2b036..57cd05f 100644
--- a/src/rebar_prv_install_deps.erl
+++ b/src/rebar_prv_install_deps.erl
@@ -97,6 +97,8 @@ do(State) ->
     end.
 
 -spec format_error(any()) -> iolist().
+format_error({load_registry_fail, Dep}) ->
+    io_lib:format("Error loading registry to resolve version of ~s. Try fixing by running 'rebar3 update'", [Dep]);
 format_error({bad_constraint, Name, Constraint}) ->
     io_lib:format("Unable to parse version for package ~s: ~s", [Name, Constraint]);
 format_error({parse_dep, Dep}) ->
@@ -129,9 +131,10 @@ handle_deps(Profile, State, Deps, Locks) when is_list(Locks) ->
                  -> {ok, [rebar_app_info:t()], rebar_state:t()} | {error, string()}.
 handle_deps(_Profile, State, [], _, _) ->
     {ok, [], State};
-handle_deps(Profile, State, Deps, Upgrade, Locks) ->
+handle_deps(Profile, State0, Deps, Upgrade, Locks) ->
     %% Read in package index and dep graph
-    {Packages, Graph} = rebar_packages:get_packages(State),
+    {Packages, Graph} = rebar_state:packages(State0),
+    State = rebar_state:packages(State0, {Packages, Graph}),
     %% Split source deps from pkg deps, needed to keep backwards compatibility
     DepsDir = rebar_dir:deps_dir(State),
     {SrcDeps, PkgDeps} = parse_deps(DepsDir, Deps, State, Locks, 0),
@@ -210,8 +213,8 @@ handle_pkg_dep(Profile, Pkg, Packages, Upgrade, DepsDir, Fetched, Seen, State) -
     AppInfo = package_to_app(DepsDir, Packages, Pkg),
     Level = rebar_app_info:dep_level(AppInfo),
     {NewSeen, NewState} = maybe_lock(Profile, AppInfo, Seen, State, Level),
-    maybe_fetch(AppInfo, Upgrade, Seen, NewState),
-    {[AppInfo | Fetched], NewSeen, NewState}.
+    {_, AppInfo1} = maybe_fetch(AppInfo, Upgrade, Seen, NewState),
+    {[AppInfo1 | Fetched], NewSeen, NewState}.
 
 maybe_lock(Profile, AppInfo, Seen, State, Level) ->
     case rebar_app_info:is_checkout(AppInfo) of
@@ -312,8 +315,8 @@ update_unseen_src_dep(AppInfo, Profile, Level, SrcDeps, PkgDeps, SrcApps, State,
                 handle_upgrade(AppInfo, SrcDeps, PkgDeps, SrcApps,
                                Level, State1, Locks);
             _ ->
-                maybe_fetch(AppInfo, false, Seen, State1),
-                handle_dep(AppInfo, SrcDeps, PkgDeps, SrcApps,
+                {_, AppInfo1} = maybe_fetch(AppInfo, false, Seen, State1),
+                handle_dep(AppInfo1, SrcDeps, PkgDeps, SrcApps,
                            Level, State1, Locks)
         end,
     {NewSrcDeps, NewPkgDeps, NewSrcApps, State2, NewSeen, NewLocks}.
@@ -323,12 +326,12 @@ handle_upgrade(AppInfo, SrcDeps, PkgDeps, SrcApps, Level, State, Locks) ->
     case lists:keyfind(Name, 1, Locks) of
         false ->
             case maybe_fetch(AppInfo, true, sets:new(), State) of
-                true ->
-                    handle_dep(AppInfo, SrcDeps, PkgDeps, SrcApps,
+                {true, AppInfo1} ->
+                    handle_dep(AppInfo1, SrcDeps, PkgDeps, SrcApps,
                                Level, State, Locks);
 
-                false ->
-                    {[AppInfo|SrcDeps], PkgDeps, SrcApps, State, Locks}
+                {false, AppInfo1} ->
+                    {[AppInfo1|SrcDeps], PkgDeps, SrcApps, State, Locks}
             end;
         _StillLocked ->
             {[AppInfo|SrcDeps], PkgDeps, SrcApps, State, Locks}
@@ -371,31 +374,37 @@ handle_dep(State, DepsDir, AppInfo, Locks, Level) ->
     {AppInfo2, SrcDeps, PkgDeps, Locks++NewLocks, State1}.
 
 -spec maybe_fetch(rebar_app_info:t(), boolean() | {true, binary(), integer()},
-                  sets:set(binary()), rebar_state:t()) -> boolean().
+                  sets:set(binary()), rebar_state:t()) -> {boolean(), rebar_app_info:t()}.
 maybe_fetch(AppInfo, Upgrade, Seen, State) ->
     AppDir = ec_cnv:to_list(rebar_app_info:dir(AppInfo)),
     %% Don't fetch dep if it exists in the _checkouts dir
     case rebar_app_info:is_checkout(AppInfo) of
         true ->
-            false;
+            {false, AppInfo};
         false ->
             case rebar_app_discover:find_app(AppDir, all) of
                 false ->
                     case in_default(AppInfo, State) of
                         false ->
-                            fetch_app(AppInfo, AppDir, State);
+                            {fetch_app(AppInfo, AppDir, State), AppInfo};
                         {true, FoundApp} ->
+                            %% Preserve the state we created with overrides
+                            AppState = rebar_app_info:state(AppInfo),
+                            FoundApp = rebar_app_info:state(FoundApp, AppState),
                             ?INFO("Linking ~s to ~s", [rebar_app_info:dir(FoundApp), AppDir]),
                             filelib:ensure_dir(AppDir),
                             rebar_file_utils:symlink_or_copy(rebar_app_info:dir(FoundApp), AppDir),
-                            true
+                            {true, AppInfo}
                     end;
-                {true, _} ->
+                {true, AppInfo1} ->
+                    %% Preserve the state we created with overrides
+                    AppState = rebar_app_info:state(AppInfo),
+                    AppInfo2 = rebar_app_info:state(AppInfo1, AppState),
                     case sets:is_element(rebar_app_info:name(AppInfo), Seen) of
                         true ->
-                            false;
+                            {false, AppInfo2};
                         false ->
-                            maybe_upgrade(AppInfo, AppDir, Upgrade, State)
+                            {maybe_upgrade(AppInfo, AppDir, Upgrade, State), AppInfo2}
                     end
             end
     end.
@@ -439,13 +448,14 @@ parse_dep({Name, Vsn}, {SrcDepsAcc, PkgDepsAcc}, DepsDir, State) when is_list(Vs
                                     ,ec_cnv:to_binary(Vsn)) | PkgDepsAcc]}
     end;
 parse_dep(Name, {SrcDepsAcc, PkgDepsAcc}, DepsDir, State) when is_atom(Name) ->
+    {PkgName, PkgVsn} = get_package(ec_cnv:to_binary(Name), State),
     CheckoutsDir = ec_cnv:to_list(rebar_dir:checkouts_dir(State, Name)),
     case rebar_app_info:discover(CheckoutsDir) of
         {ok, _App} ->
             Dep = new_dep(DepsDir, Name, [], [], State),
             {[Dep | SrcDepsAcc], PkgDepsAcc};
         not_found ->
-            {SrcDepsAcc, [ec_cnv:to_binary(Name) | PkgDepsAcc]}
+            {SrcDepsAcc, [{PkgName, PkgVsn} | PkgDepsAcc]}
     end;
 parse_dep({Name, Source}, {SrcDepsAcc, PkgDepsAcc}, DepsDir, State) when is_tuple(Source) ->
     Dep = new_dep(DepsDir, Name, [], Source, State),
@@ -561,3 +571,12 @@ warn_skip_pkg({Name, Source}, State) ->
 not_needs_compile(App) ->
     not(rebar_app_info:is_checkout(App))
         andalso rebar_app_info:valid(App).
+
+get_package(Dep, State) ->
+    case rebar_packages:registry(State) of
+        {ok, T} ->
+            HighestDepVsn = rebar_packages:find_highest_matching(Dep, "0", T),
+            {Dep, HighestDepVsn};
+        error ->
+            throw(?PRV_ERROR({load_registry_fail, Dep}))
+    end.
diff --git a/src/rebar_prv_packages.erl b/src/rebar_prv_packages.erl
index 8ba9e92..c7c0d50 100644
--- a/src/rebar_prv_packages.erl
+++ b/src/rebar_prv_packages.erl
@@ -7,6 +7,8 @@
          format_error/1]).
 
 -include("rebar.hrl").
+-include_lib("stdlib/include/ms_transform.hrl").
+-include_lib("providers/include/providers.hrl").
 
 -define(PROVIDER, pkgs).
 -define(DEPS, []).
@@ -25,33 +27,26 @@ init(State) ->
 
 -spec do(rebar_state:t()) -> {ok, rebar_state:t()} | {error, string()}.
 do(State) ->
-    {Packages, _Graph} = rebar_packages:get_packages(State),
-    print_packages(Packages),
-    {ok, State}.
+    case rebar_packages:registry(State) of
+        {ok, Registry} ->
+            print_packages(Registry),
+            {ok, State};
+        error ->
+            ?PRV_ERROR(load_registry_fail)
+    end.
 
 -spec format_error(any()) -> iolist().
-format_error(Reason) ->
-    io_lib:format("~p", [Reason]).
+format_error(load_registry_fail) ->
+    "Failed to load package regsitry. Try running 'rebar3 update' to fix".
 
-print_packages(Packages) ->
-    Keys = lists:keysort(1, dict:fetch_keys(Packages)),
-    Pkgs = merge(Keys),
+print_packages(Table) ->
+    MS = ets:fun2ms(fun({Key, [Value]}) when is_binary(Key) -> {Key, Value} end),
+    Pkgs = ets:select(Table, MS),
     lists:foreach(fun({Name, Vsns}) ->
                           VsnStr = join(Vsns, <<", ">>),
                           io:format("~s:~n    Versions: ~s~n~n", [Name, VsnStr])
                   end, Pkgs).
 
--spec merge([{binary(), binary()}]) -> [{binary(), [binary()]}].
-merge(List) ->
-    merge([], List).
-
-merge(List, []) ->
-    List;
-merge([{Key, Values} | T], [{Key, Value} | Rest]) ->
-    merge([{Key, [Value | Values]} | T], Rest);
-merge(List, [{Key, Value} | Rest]) ->
-    merge([{Key, [Value]} | List], Rest).
-
 -spec join([binary()], binary()) -> binary().
 join([Bin], _Sep) ->
     <<Bin/binary>>;
diff --git a/src/rebar_prv_update.erl b/src/rebar_prv_update.erl
index be5cafd..6cdabeb 100644
--- a/src/rebar_prv_update.erl
+++ b/src/rebar_prv_update.erl
@@ -35,10 +35,14 @@ init(State) ->
 do(State) ->
     ?INFO("Updating package index...", []),
     try
-        Url = rebar_state:get(State, rebar_packages_cdn, "https://s3.amazonaws.com/s3.hex.pm/registry.ets.gz"),
+        Dir = rebar_dir:global_cache_dir(State),
+        RegistryDir = filename:join(Dir, "packages"),
+        filelib:ensure_dir(filename:join(RegistryDir, "dummy")),
+        HexFile = filename:join(RegistryDir, "registry"),
         TmpDir = ec_file:insecure_mkdtemp(),
         TmpFile = filename:join(TmpDir, "packages.gz"),
-        HexFile = filename:join(TmpDir, "packages"),
+
+        Url = rebar_state:get(State, rebar_packages_cdn, "https://s3.amazonaws.com/s3.hex.pm/registry.ets.gz"),
         {ok, _RequestId} = httpc:request(get, {Url, []},
                                          [], [{stream, TmpFile}, {sync, true}]),
         {ok, Data} = file:read_file(TmpFile),
@@ -90,7 +94,7 @@ update_graph(Pkg, PkgVsn, Deps, HexRegistry, Graph) ->
     lists:foldl(fun([Dep, DepVsn, _, _], DepsListAcc) ->
                         case DepVsn of
                             <<"~> ", Vsn/binary>> ->
-                                HighestDepVsn = find_highest_matching(Dep, Vsn, HexRegistry),
+                                HighestDepVsn = rebar_packages:find_highest_matching(Dep, Vsn, HexRegistry),
                                 digraph:add_edge(Graph, {Pkg, PkgVsn}, {Dep, HighestDepVsn}),
                                 [{Dep, DepVsn} | DepsListAcc];
                             Vsn ->
@@ -98,41 +102,3 @@ update_graph(Pkg, PkgVsn, Deps, HexRegistry, Graph) ->
                                 [{Dep, Vsn} | DepsListAcc]
                         end
                 end, [], Deps).
-
-%% Hex supports use of ~> to specify the version required for a dependency.
-%% Since rebar3 requires exact versions to choose from we find the highest
-%% available version of the dep that passes the constraint.
-
-%% `~>` will never include pre-release versions of its upper bound.
-%% It can also be used to set an upper bound on only the major
-%% version part. See the table below for `~>` requirements and
-%% their corresponding translation.
-%% `~>` | Translation
-%% :------------- | :---------------------
-%% `~> 2.0.0` | `>= 2.0.0 and < 2.1.0`
-%% `~> 2.1.2` | `>= 2.1.2 and < 2.2.0`
-%% `~> 2.1.3-dev` | `>= 2.1.3-dev and < 2.2.0`
-%% `~> 2.0` | `>= 2.0.0 and < 3.0.0`
-%% `~> 2.1` | `>= 2.1.0 and < 3.0.0`
-find_highest_matching(Dep, Constraint, T) ->
-    case ets:lookup(T, Dep) of
-        [{Dep, [[Vsn]]}] ->
-            case ec_semver:pes(Vsn, Constraint) of
-                true ->
-                    Vsn;
-                false ->
-                    ?WARN("Only existing version of ~s is ~s which does not match constraint ~~> ~s. "
-                         "Using anyway, but it is not guarenteed to work.", [Dep, Vsn, Constraint]),
-                    Vsn
-            end;
-        [{Dep, [[HeadVsn | VsnTail]]}] ->
-            lists:foldl(fun(Version, Highest) ->
-                                case ec_semver:pes(Version, Constraint) andalso
-                                    ec_semver:gt(Version, Highest) of
-                                    true ->
-                                        Version;
-                                    false ->
-                                        Highest
-                                end
-                        end, HeadVsn, VsnTail)
-    end.
diff --git a/src/rebar_state.erl b/src/rebar_state.erl
index 68c71a9..af875d7 100644
--- a/src/rebar_state.erl
+++ b/src/rebar_state.erl
@@ -30,6 +30,8 @@
          overrides/1, overrides/2,
          apply_overrides/2,
 
+         packages/1, packages/2,
+
          resources/1, resources/2, add_resource/2,
          providers/1, providers/2, add_provider/2]).
 
@@ -51,6 +53,8 @@
                   deps_to_build       = []          :: [rebar_app_info:t()],
                   all_deps            = []          :: [rebar_app_info:t()],
 
+                  packages            = undefined   :: {rebar_dict(), rebar_digraph()} | undefined,
+
                   overrides           = [],
                   resources           = [],
                   providers           = []}).
@@ -242,7 +246,8 @@ merge_opts(NewOpts, OldOpts) ->
                            true ->
                                NewValue;
                            false ->
-                               tup_umerge(tup_sort(NewValue), tup_sort(OldValue))
+                               rebar_utils:tup_umerge(rebar_utils:tup_sort(NewValue)
+                                                     ,rebar_utils:tup_sort(OldValue))
                        end;
                   (_Key, NewValue, _OldValue) ->
                        NewValue
@@ -298,6 +303,14 @@ namespace(#state_t{namespace=Namespace}) ->
 namespace(State=#state_t{}, Namespace) ->
     State#state_t{namespace=Namespace}.
 
+packages(State=#state_t{packages=undefined}) ->
+    rebar_packages:get_packages(State);
+packages(#state_t{packages=Packages}) ->
+    Packages.
+
+packages(State, Packages) ->
+    State#state_t{packages=Packages}.
+
 -spec resources(t()) -> rebar_resource:resource().
 resources(#state_t{resources=Resources}) ->
     Resources.
@@ -340,65 +353,3 @@ create_logic_providers(ProviderModules, State0) ->
 %% ===================================================================
 %% Internal functions
 %% ===================================================================
-
-%% Sort the list in proplist-order, meaning that `{a,b}' and `{a,c}'
-%% both compare as usual, and `a' and `b' do the same, but `a' and `{a,b}' will
-%% compare based on the first element of the key, and in order. So the following
-%% list will sort as:
-%% - `[native, {native,o3}, check]' -> `[check, native, {native, o3}]'
-%% - `[native, {native,o3}, {native, o2}, check]' -> `[check,native,{native,o3},{native,o2}]'
-%% Meaning that:
-%% a) no deduplication takes place
-%% b) the key of a tuple is what counts in being sorted, but atoms are seen as {atom}
-%%    as far as comparison is concerned (departing from lists:ukeysort/2)
-%% c) order is preserved for similar keys and tuples no matter their size (sort is stable)
-%%
-%% These properties let us merge proplists fairly easily.
-tup_sort(List) ->
-    lists:sort(fun(A, B) when is_tuple(A), is_tuple(B) -> element(1, A) =< element(1, B)
-               ;  (A, B) when is_tuple(A) -> element(1, A) =< B
-               ;  (A, B) when is_tuple(B) -> A =< element(1, B)
-               ;  (A, B) -> A =< B
-               end, List).
-
-%% Custom merge functions. The objective is to behave like lists:umerge/2,
-%% except that we also compare the merge elements based on the key if they're a
-%% tuple, such that `{key, val1}' is always prioritized over `{key, val0}' if
-%% the former is from the 'new' list.
-%%
-%% This lets us apply proper overrides to list of elements according to profile
-%% priority. This function depends on a stable proplist sort.
-tup_umerge([], Olds) ->
-    Olds;
-tup_umerge([New|News], Olds) ->
-    lists:reverse(umerge(News, Olds, [], New)).
-
-%% This is equivalent to umerge2_2 in the stdlib, except we use the expanded
-%% value/key only to compare
-umerge(News, [Old|Olds], Merged, Cmp) when element(1, Cmp) == element(1, Old);
-                                           element(1, Cmp) == Old;
-                                           Cmp == element(1, Old);
-                                           Cmp =< Old ->
-    umerge(News, Olds, [Cmp | Merged], Cmp, Old);
-umerge(News, [Old|Olds], Merged, Cmp) ->
-    umerge(News, Olds, [Old | Merged], Cmp);
-umerge(News, [], Merged, Cmp) ->
-    lists:reverse(News, [Cmp | Merged]).
-
-%% Similar to stdlib's umerge2_1 in the stdlib, except that when the expanded
-%% value/keys compare equal, we check if the element is a full dupe to clear it
-%% (like the stdlib function does) or otherwise keep the duplicate around in
-%% an order that prioritizes 'New' elements.
-umerge([New|News], Olds, Merged, CmpMerged, Cmp) when CmpMerged == Cmp ->
-    umerge(News, Olds, Merged, New);
-umerge([New|News], Olds, Merged, _CmpMerged, Cmp) when element(1,New) == element(1, Cmp);
-                                                       element(1,New) == Cmp;
-                                                       New == element(1, Cmp);
-                                                       New =< Cmp ->
-    umerge(News, Olds, [New | Merged], New, Cmp);
-umerge([New|News], Olds, Merged, _CmpMerged, Cmp) -> % >
-    umerge(News, Olds, [Cmp | Merged], New);
-umerge([], Olds, Merged, CmpMerged, Cmp) when CmpMerged == Cmp ->
-    lists:reverse(Olds, Merged);
-umerge([], Olds, Merged, _CmpMerged, Cmp) ->
-    lists:reverse(Olds, [Cmp | Merged]).
diff --git a/src/rebar_utils.erl b/src/rebar_utils.erl
index d92ab80..bc2e4ac 100644
--- a/src/rebar_utils.erl
+++ b/src/rebar_utils.erl
@@ -52,7 +52,9 @@
          args_to_tasks/1,
          expand_env_variable/3,
          get_arch/0,
-         wordsize/0]).
+         wordsize/0,
+         tup_umerge/2,
+         tup_sort/1]).
 
 %% for internal use only
 -export([otp_release/0]).
@@ -225,6 +227,68 @@ erl_opts(Config) ->
 %%  was enclosed in quotes and might have commas but should not be split.
 args_to_tasks(Args) -> new_task(Args, []).
 
+%% Sort the list in proplist-order, meaning that `{a,b}' and `{a,c}'
+%% both compare as usual, and `a' and `b' do the same, but `a' and `{a,b}' will
+%% compare based on the first element of the key, and in order. So the following
+%% list will sort as:
+%% - `[native, {native,o3}, check]' -> `[check, native, {native, o3}]'
+%% - `[native, {native,o3}, {native, o2}, check]' -> `[check,native,{native,o3},{native,o2}]'
+%% Meaning that:
+%% a) no deduplication takes place
+%% b) the key of a tuple is what counts in being sorted, but atoms are seen as {atom}
+%%    as far as comparison is concerned (departing from lists:ukeysort/2)
+%% c) order is preserved for similar keys and tuples no matter their size (sort is stable)
+%%
+%% These properties let us merge proplists fairly easily.
+tup_sort(List) ->
+    lists:sort(fun(A, B) when is_tuple(A), is_tuple(B) -> element(1, A) =< element(1, B)
+               ;  (A, B) when is_tuple(A) -> element(1, A) =< B
+               ;  (A, B) when is_tuple(B) -> A =< element(1, B)
+               ;  (A, B) -> A =< B
+               end, List).
+
+%% Custom merge functions. The objective is to behave like lists:umerge/2,
+%% except that we also compare the merge elements based on the key if they're a
+%% tuple, such that `{key, val1}' is always prioritized over `{key, val0}' if
+%% the former is from the 'new' list.
+%%
+%% This lets us apply proper overrides to list of elements according to profile
+%% priority. This function depends on a stable proplist sort.
+tup_umerge([], Olds) ->
+    Olds;
+tup_umerge([New|News], Olds) ->
+    lists:reverse(umerge(News, Olds, [], New)).
+
+%% This is equivalent to umerge2_2 in the stdlib, except we use the expanded
+%% value/key only to compare
+umerge(News, [Old|Olds], Merged, Cmp) when element(1, Cmp) == element(1, Old);
+                                           element(1, Cmp) == Old;
+                                           Cmp == element(1, Old);
+                                           Cmp =< Old ->
+    umerge(News, Olds, [Cmp | Merged], Cmp, Old);
+umerge(News, [Old|Olds], Merged, Cmp) ->
+    umerge(News, Olds, [Old | Merged], Cmp);
+umerge(News, [], Merged, Cmp) ->
+    lists:reverse(News, [Cmp | Merged]).
+
+%% Similar to stdlib's umerge2_1 in the stdlib, except that when the expanded
+%% value/keys compare equal, we check if the element is a full dupe to clear it
+%% (like the stdlib function does) or otherwise keep the duplicate around in
+%% an order that prioritizes 'New' elements.
+umerge([New|News], Olds, Merged, CmpMerged, Cmp) when CmpMerged == Cmp ->
+    umerge(News, Olds, Merged, New);
+umerge([New|News], Olds, Merged, _CmpMerged, Cmp) when element(1,New) == element(1, Cmp);
+                                                       element(1,New) == Cmp;
+                                                       New == element(1, Cmp);
+                                                       New =< Cmp ->
+    umerge(News, Olds, [New | Merged], New, Cmp);
+umerge([New|News], Olds, Merged, _CmpMerged, Cmp) -> % >
+    umerge(News, Olds, [Cmp | Merged], New);
+umerge([], Olds, Merged, CmpMerged, Cmp) when CmpMerged == Cmp ->
+    lists:reverse(Olds, Merged);
+umerge([], Olds, Merged, _CmpMerged, Cmp) ->
+    lists:reverse(Olds, [Cmp | Merged]).
+
 %% ====================================================================
 %% Internal functions
 %% ====================================================================