Key already returned dependencies on repo and package

lib/hex_solver/package_lister.ex

@@ -133,7 +133,8 @@ defmodule HexSolver.PackageLister do
     lister = %{
       lister
       | already_prefetched: MapSet.union(lister.already_prefetched, prefetch),
-        already_returned: Map.put(lister.already_returned, package, already_returned)
+        already_returned:
+          Map.put(lister.already_returned, {package_repo, package}, already_returned)
     }
 
     {lister, incompatibilities}

test/hex_solver/package_lister_test.exs

@@ -0,0 +1,41 @@
+defmodule HexSolver.PackageListerTest do
+  use HexSolver.Case, async: true
+
+  alias HexSolver.PackageLister
+  alias HexSolver.Registry.Process, as: Registry
+
+  describe "dependencies_as_incompatibilities/4" do
+    test "skips dependencies already returned for the version" do
+      Registry.put("foo", "1.0.0", [{"bar", "~> 1.0"}])
+      Registry.put("foo", "2.0.0", [{"bar", "~> 1.0"}])
+      Registry.put("bar", "1.0.0", [])
+      Registry.prefetch([{nil, "foo"}])
+
+      lister = %PackageLister{registry: Registry}
+
+      assert {lister, [incompatibility]} =
+               PackageLister.dependencies_as_incompatibilities(lister, nil, "foo", v("2.0.0"))
+
+      assert to_string(incompatibility) ==
+               ~s(every version of "foo" depends on "bar ~> 1.0")
+
+      assert {_lister, []} =
+               PackageLister.dependencies_as_incompatibilities(lister, nil, "foo", v("1.0.0"))
+    end
+
+    test "returns dependencies again for a package with the same name in another repo" do
+      Registry.put("foo", "1.0.0", [{"bar", "~> 1.0"}])
+      Registry.put("repo", "foo", "1.0.0", [{"bar", "~> 1.0"}])
+      Registry.put("bar", "1.0.0", [])
+      Registry.prefetch([{nil, "foo"}, {"repo", "foo"}])
+
+      lister = %PackageLister{registry: Registry}
+
+      assert {lister, [_incompatibility]} =
+               PackageLister.dependencies_as_incompatibilities(lister, nil, "foo", v("1.0.0"))
+
+      assert {_lister, [_incompatibility]} =
+               PackageLister.dependencies_as_incompatibilities(lister, "repo", "foo", v("1.0.0"))
+    end
+  end
+end