Reject non fullfilled optional dependencies later on

Imagine this dependency tree:

    * parent
      * child
        * ecto
        * postgrex
      * ja_serializer
        * ecto

where postgrex is an optional dependency of Ecto.

Because optional dependencies were rejected later on,
ecto would have its postgrex dependency stripped and
later failed to top-sort. This commit changes it to
so optional dependencies are rejected only later on.

Signed-off-by: José Valim <[email protected]>

Author: José Valim

lib/mix/lib/mix/dep/converger.ex

@@ -92,15 +92,18 @@ defmodule Mix.Dep.Converger do
       # In case no lock was given, we will use the local lock
       # which is potentially stale. So remote.deps/2 needs to always
       # check if the data it finds in the lock is actually valid.
-      all(main, apps, callback, rest, lock, env, fn dep ->
-        if cached = deps[dep.app] do
-          {:loaded, cached}
-        else
-          {:unloaded, dep, remote.deps(dep, lock)}
-        end
-      end)
+      {deps, rest, lock} =
+        all(main, apps, callback, rest, lock, env, fn dep ->
+          if cached = deps[dep.app] do
+            {:loaded, cached}
+          else
+            {:unloaded, dep, remote.deps(dep, lock)}
+          end
+        end)
+
+      {reject_non_fullfilled_optional(deps), rest, lock}
     else
-      {deps, rest, lock}
+      {reject_non_fullfilled_optional(deps), rest, lock}
     end
   end
 
@@ -173,12 +176,12 @@ defmodule Mix.Dep.Converger do
               Mix.Dep.Loader.load(dep, children)
           end
 
-        dep = %{dep | deps: reject_non_fullfilled_optional(dep.deps, current_breadths)}
         {acc, rest, lock} =
           all(t, [dep|acc], upper_breadths, current_breadths, callback, rest, lock, env, cache)
 
-        new_breadths = Enum.map(dep.deps, &(&1.app)) ++ current_breadths
-        all(dep.deps, acc, current_breadths, new_breadths, callback, rest, lock, env, cache)
+        deps = reject_non_fullfilled_optional(dep.deps, current_breadths)
+        new_breadths = Enum.map(deps, &(&1.app)) ++ current_breadths
+        all(deps, acc, current_breadths, new_breadths, callback, rest, lock, env, cache)
     end
   end
 
@@ -286,6 +289,13 @@ defmodule Mix.Dep.Converger do
     Enum.all?(keys, &(Keyword.fetch(opts1, &1) == Keyword.fetch(opts2, &1)))
   end
 
+  defp reject_non_fullfilled_optional(deps) do
+    apps = Enum.map(deps, & &1.app)
+    for dep <- deps do
+      update_in dep.deps, &reject_non_fullfilled_optional(&1, apps)
+    end
+  end
+
   defp reject_non_fullfilled_optional(children, upper_breadths) do
     Enum.reject children, fn %Mix.Dep{app: app, opts: opts} ->
       opts[:optional] && not(app in upper_breadths)