Fix PartitionSupervisor.count_children/1 and stop/3 to support via tuples (#15161)

The `name()` type for PartitionSupervisor includes `{:via, module(), term()}`
tuples, but `count_children/1` and `stop/3` only accepted atoms, raising
`FunctionClauseError` for via tuples.

Author: pnezis

lib/elixir/lib/partition_supervisor.ex

@@ -170,6 +170,8 @@ defmodule PartitionSupervisor do
           | {:max_seconds, non_neg_integer()}
           | {:with_arguments, (args :: [term()], partition() -> updated_args :: [term()])}
 
+  defguardp is_name(name) when is_atom(name) or elem(name, 0) == :via
+
   @doc false
   def child_spec(opts) when is_list(opts) do
     id =
@@ -366,7 +368,7 @@ defmodule PartitionSupervisor do
   """
   @doc since: "1.18.0"
   @spec resize!(name(), non_neg_integer()) :: non_neg_integer()
-  def resize!(name, partitions) when is_integer(partitions) do
+  def resize!(name, partitions) when is_name(name) and is_integer(partitions) do
     supervisor =
       GenServer.whereis(name) || exit({:noproc, {__MODULE__, :resize!, [name, partitions]}})
 
@@ -422,7 +424,7 @@ defmodule PartitionSupervisor do
   """
   @doc since: "1.14.0"
   @spec partitions(name()) :: non_neg_integer()
-  def partitions(name) do
+  def partitions(name) when is_name(name) do
     name |> table() |> partitions(name)
   end
 
@@ -470,7 +472,7 @@ defmodule PartitionSupervisor do
           # Inlining [module()] | :dynamic here because :supervisor.modules() is not exported
           {integer(), pid | :restarting, :worker | :supervisor, [module()] | :dynamic}
         ]
-  def which_children(name) when is_atom(name) or elem(name, 0) == :via do
+  def which_children(name) when is_name(name) do
     Supervisor.which_children(name)
   end
 
@@ -498,7 +500,7 @@ defmodule PartitionSupervisor do
           supervisors: non_neg_integer,
           workers: non_neg_integer
         }
-  def count_children(supervisor) when is_atom(supervisor) do
+  def count_children(supervisor) when is_name(supervisor) do
     Supervisor.count_children(supervisor)
   end
 
@@ -514,7 +516,7 @@ defmodule PartitionSupervisor do
   """
   @doc since: "1.14.0"
   @spec stop(name(), reason :: term, timeout) :: :ok
-  def stop(supervisor, reason \\ :normal, timeout \\ :infinity) when is_atom(supervisor) do
+  def stop(supervisor, reason \\ :normal, timeout \\ :infinity) when is_name(supervisor) do
     Supervisor.stop(supervisor, reason, timeout)
   end
 

lib/elixir/test/elixir/partition_supervisor_test.exs

@@ -147,6 +147,22 @@ defmodule PartitionSupervisorTest do
       assert PartitionSupervisor.stop(config.test) == :ok
       assert Process.whereis(config.test) == nil
     end
+
+    test "with via tuple", config do
+      {:ok, _} = Registry.start_link(keys: :unique, name: config.test)
+
+      name = {:via, Registry, {config.test, :stop_test}}
+
+      {:ok, pid} =
+        PartitionSupervisor.start_link(
+          child_spec: {Agent, fn -> %{} end},
+          name: name
+        )
+
+      assert Process.alive?(pid)
+      assert PartitionSupervisor.stop(name) == :ok
+      refute Process.alive?(pid)
+    end
   end
 
   describe "partitions/1" do
@@ -272,5 +288,22 @@ defmodule PartitionSupervisorTest do
     test "raises noproc for unknown partition supervisor" do
       assert {:noproc, _} = catch_exit(PartitionSupervisor.count_children(:unknown))
     end
+
+    test "with via tuple", config do
+      {:ok, _} = Registry.start_link(keys: :unique, name: config.test)
+
+      name = {:via, Registry, {config.test, :count_test}}
+
+      {:ok, _} =
+        PartitionSupervisor.start_link(
+          child_spec: {Agent, fn -> %{} end},
+          name: name
+        )
+
+      partitions = System.schedulers_online()
+
+      assert PartitionSupervisor.count_children(name) ==
+               %{active: partitions, specs: partitions, supervisors: 0, workers: partitions}
+    end
   end
 end