Add tests for lock forwarding

Lock forwarding is what happens when the file on disk are on a different
version from what is specified in the lock file. Files on disk should be
updated to respect what's in the lock file.

A negative test has been added so that lock files that are outdated vis.
the underlying git and packages but match files on disk do not get
forwarded. This job is left to the `upgrade' command.

test/rebar_upgrade_SUITE.erl

@@ -10,7 +10,7 @@ groups() ->
                 pair_a, pair_b, pair_ab, pair_c, pair_all,
                 triplet_a, triplet_b, triplet_c,
                 tree_a, tree_b, tree_c, tree_c2, tree_ac, tree_all,
-                delete_d, promote]},
+                delete_d, promote, stable_lock, fwd_lock]},
      {git, [], [{group, all}]},
      {pkg, [], [{group, all}]}].
 
@@ -361,7 +361,30 @@ upgrades(promote) ->
       {"C", "3", []}
      ],
      ["A","B","C","D"],
-     {"C", [{"A","1"},{"C","3"},{"B","1"},{"D","1"}]}}.
+     {"C", [{"A","1"},{"C","3"},{"B","1"},{"D","1"}]}};
+upgrades(stable_lock) ->
+    {[{"A", "1", [{"C", "1", []}]},
+      {"B", "1", [{"D", "1", []}]}
+     ], % lock after this
+     [{"A", "2", [{"C", "2", []}]},
+      {"B", "2", [{"D", "2", []}]}
+     ],
+     ["A","B","C","D"],
+     %% Run a regular lock and no app should be upgraded
+     {"any", [{"A","1"},{"C","1"},{"B","1"},{"D","1"}]}};
+upgrades(fwd_lock) ->
+    {[{"A", "1", [{"C", "1", []}]},
+      {"B", "1", [{"D", "1", []}]}
+     ],
+     [{"A", "2", [{"C", "2", []}]},
+      {"B", "2", [{"D", "2", []}]}
+     ],
+     ["A","B","C","D"],
+     %% For this one, we should build, rewrite the lock
+     %% file to include the result post-upgrade, and then
+     %% run a regular lock to see that the lock file is respected
+     %% in deps.
+     {"any", [{"A","2"},{"C","2"},{"B","2"},{"D","2"}]}}.
 
 %% TODO: add a test that verifies that unlocking files and then
 %% running the upgrade code is enough to properly upgrade things.
@@ -435,6 +458,46 @@ delete_d(Config) ->
     ?assertNotEqual([],
                     [1 || {"App ~ts is no longer needed and can be deleted.",
                            [<<"D">>]} <- Infos]).
+
+stable_lock(Config) ->
+    apply(?config(mock, Config), []),
+    {ok, RebarConfig} = file:consult(?config(rebarconfig, Config)),
+    %% Install dependencies before re-mocking for an upgrade
+    rebar_test_utils:run_and_check(Config, RebarConfig, ["lock"], {ok, []}),
+    {App, Unlocks} = ?config(expected, Config),
+    ct:pal("Upgrades: ~p -> ~p", [App, Unlocks]),
+    Expectation = case Unlocks of
+        {error, Term} -> {error, Term};
+        _ -> {ok, Unlocks}
+    end,
+    apply(?config(mock_update, Config), []),
+    NewRebarConf = rebar_test_utils:create_config(?config(apps, Config),
+                                                  [{deps, ?config(next_top_deps, Config)}]),
+    {ok, NewRebarConfig} = file:consult(NewRebarConf),
+    rebar_test_utils:run_and_check(
+        Config, NewRebarConfig, ["lock", App], Expectation
+    ).
+
+fwd_lock(Config) ->
+    apply(?config(mock, Config), []),
+    {ok, RebarConfig} = file:consult(?config(rebarconfig, Config)),
+    %% Install dependencies before re-mocking for an upgrade
+    rebar_test_utils:run_and_check(Config, RebarConfig, ["lock"], {ok, []}),
+    {App, Unlocks} = ?config(expected, Config),
+    ct:pal("Upgrades: ~p -> ~p", [App, Unlocks]),
+    Expectation = case Unlocks of
+        {error, Term} -> {error, Term};
+        _ -> {ok, Unlocks}
+    end,
+    rewrite_locks(Expectation, Config),
+    apply(?config(mock_update, Config), []),
+    NewRebarConf = rebar_test_utils:create_config(?config(apps, Config),
+                                                  [{deps, ?config(next_top_deps, Config)}]),
+    {ok, NewRebarConfig} = file:consult(NewRebarConf),
+    rebar_test_utils:run_and_check(
+        Config, NewRebarConfig, ["lock", App], Expectation
+    ).
+
 run(Config) ->
     apply(?config(mock, Config), []),
     {ok, RebarConfig} = file:consult(?config(rebarconfig, Config)),
@@ -453,3 +516,20 @@ run(Config) ->
     rebar_test_utils:run_and_check(
         Config, NewRebarConfig, ["upgrade", App], Expectation
     ).
+
+rewrite_locks({ok, Expectations}, Config) ->
+    AppDir = ?config(apps, Config),
+    LockFile = filename:join([AppDir, "rebar.lock"]),
+    {ok, [Locks]} = file:consult(LockFile),
+    ExpLocks = [{list_to_binary(Name), Vsn}
+               || {lock, Name, Vsn} <- Expectations],
+    NewLocks = lists:foldl(
+        fun({App, {pkg, Name, _}, Lvl}, Acc) ->
+                Vsn = list_to_binary(proplists:get_value(App,ExpLocks)),
+                [{App, {pkg, Name, Vsn}, Lvl} | Acc]
+        ;  ({App, {git, URL, {ref, _}}, Lvl}, Acc) ->
+                Vsn = proplists:get_value(App,ExpLocks),
+                [{App, {git, URL, {ref, Vsn}}, Lvl} | Acc]
+        end, [], Locks),
+    ct:pal("rewriting locks from ~p to~n~p", [Locks, NewLocks]),
+    file:write_file(LockFile, io_lib:format("~p.~n", [NewLocks])).