Safer purge switch

Rather than the caller having to think of what to purge or not, use
erlang:check_process_code/2 to detect if the caller (rebar3) may die
because of the operation.

If so, do a soft purge with a conditional delete instead of a hard purge
with a mandatory delete.

src/rebar_prv_compile.erl

@@ -145,7 +145,7 @@ compile(State, Providers, AppInfo) ->
     code:add_pathsa(PluginDepsPaths),
     AppFileCompileResult = rebar_otp_app:compile(State, AppInfo4),
     %% Clean up after ourselves, leave things as they were.
-    rebar_utils:remove_from_code_path(PluginDepsPaths, soft_purge),
+    rebar_utils:remove_from_code_path(PluginDepsPaths),
 
     case AppFileCompileResult of
         {ok, AppInfo5} ->

src/rebar_utils.erl

@@ -49,7 +49,6 @@
          update_code/1,
          update_code/2,
          remove_from_code_path/1,
-         remove_from_code_path/2,
          cleanup_code_path/1,
          args_to_tasks/1,
          expand_env_variable/3,
@@ -754,9 +753,6 @@ update_code(Paths, Opts) ->
                   end, Paths).
 
 remove_from_code_path(Paths) ->
-    remove_from_code_path(Paths, purge).
-
-remove_from_code_path(Paths, Type) when Type == purge; Type == soft_purge ->
     lists:foreach(fun(Path) ->
                           Name = filename:basename(Path, "/ebin"),
                           App = list_to_atom(Name),
@@ -767,7 +763,13 @@ remove_from_code_path(Paths, Type) when Type == purge; Type == soft_purge ->
                                   ok;
                               {ok, Modules} ->
                                   application:unload(App),
-                                  [begin code:Type(M), code:delete(M) end || M <- Modules]
+                                  [case erlang:check_process_code(self(), M) of
+                                       false ->
+                                           code:purge(M), code:delete(M);
+                                       _ ->
+                                           ?DEBUG("~p can't purge ~p safely, doing a soft purge", [self(), M]),
+                                           code:soft_purge(M) andalso code:delete(M)
+                                   end || M <- Modules]
                           end,
                           code:del_path(Path)
                   end, lists:usort(Paths)).

systest/all_SUITE.erl

@@ -66,6 +66,7 @@ alias_clash(Config) ->
     ?assertNotEqual(nomatch,
         re:run(Output, "Not adding provider default test from module rebar_prv_alias_test "
                        "because it already exists from module rebar_prv_alias_test")),
+    ok.
 
 grisp_explode() ->
     [{doc, "Don't force purge a plugin that runs the compile job itself"}].