Enforce acyclicity; check presence and export of steps.

1 files changed, 36 insertions, 4 deletions

diff --git a/src/rabbit_plugin_activator.erl b/src/rabbit_plugin_activator.erl
index 6f6dd2ed..8bf16bec 100644
--- a/src/rabbit_plugin_activator.erl
+++ b/src/rabbit_plugin_activator.erl
@@ -163,12 +163,12 @@ boot_steps(AllApps) ->
     sort_boot_steps(UnsortedSteps).
 
 sort_boot_steps(UnsortedSteps) ->
-    G = digraph:new(),
+    G = digraph:new([acyclic]),
     [digraph:add_vertex(G, ModFunSpec, Step) || Step = {ModFunSpec, _Attrs} <- UnsortedSteps],
     lists:foreach(fun ({ModFunSpec, Attributes}) ->
-                          [digraph:add_edge(G, ModFunSpec, PostModFunSpec)
+                          [add_boot_step_dep(G, ModFunSpec, PostModFunSpec)
                            || {post, PostModFunSpec} <- Attributes],
-                          [digraph:add_edge(G, PreModFunSpec, ModFunSpec)
+                          [add_boot_step_dep(G, PreModFunSpec, ModFunSpec)
                            || {pre, PreModFunSpec} <- Attributes]
                   end, UnsortedSteps),
     SortedStepsRev = [begin
@@ -177,7 +177,39 @@ sort_boot_steps(UnsortedSteps) ->
                       end || ModFunSpec <- digraph_utils:topsort(G)],
     SortedSteps = lists:reverse(SortedStepsRev),
     digraph:delete(G),
-    SortedSteps.
+    check_boot_steps(SortedSteps).
+
+add_boot_step_dep(G, RunsSecond, RunsFirst) ->
+    case digraph:add_edge(G, RunsSecond, RunsFirst) of
+        {error, Reason} ->
+            error("Could not add boot step dependency of ~s on ~s:~n~s",
+                  [format_modfunspec(RunsSecond), format_modfunspec(RunsFirst),
+                   case Reason of
+                       {bad_vertex, V} ->
+                           io_lib:format("Boot step not registered: ~s~n",
+                                         [format_modfunspec(V)]);
+                       {bad_edge, [First | Rest]} ->
+                           [io_lib:format("Cyclic dependency: ~s", [format_modfunspec(First)]),
+                            [io_lib:format(" depends on ~s", [format_modfunspec(Next)])
+                             || Next <- Rest],
+                            io_lib:format(" depends on ~s~n", [format_modfunspec(First)])]
+                   end]);
+        _ ->
+            ok
+    end.
+
+check_boot_steps(SortedSteps) ->
+    case [ModFunSpec || {ModFunSpec = {Module, {Fun, Arity}}, _} <- SortedSteps,
+                        not erlang:function_exported(Module, Fun, Arity)] of
+        [] ->
+            SortedSteps;
+        MissingFunctions ->
+            error("Boot steps not exported:~s~n",
+                  [[[" ", format_modfunspec(MFS)] || MFS <- MissingFunctions]])
+    end.
+
+format_modfunspec({Module, {Fun, Arity}}) ->
+    lists:flatten(io_lib:format("~w:~w/~b", [Module, Fun, Arity])).
 
 assert_dir(Dir) ->
     case filelib:is_dir(Dir) of