Retire use of Supervisor.Specjv-no-supervisor-spec

20 files changed, 150 insertions, 145 deletions

diff --git a/lib/elixir/lib/file.ex b/lib/elixir/lib/file.ex
index 8763e0ae6..b33731ef8 100644
--- a/lib/elixir/lib/file.ex
+++ b/lib/elixir/lib/file.ex
@@ -1260,7 +1260,7 @@ defmodule File do
   Raises an error if retrieving or changing the current
   directory fails.
   """
-  @spec cd!(Path.t, (() -> res)) :: res | no_return when res: var
+  @spec cd!(Path.t, (() -> res)) :: res when res: var
   def cd!(path, function) do
     old = cwd!()
     cd!(path)
diff --git a/lib/elixir/lib/task/supervisor.ex b/lib/elixir/lib/task/supervisor.ex
index efaa9344c..00ee816e7 100644
--- a/lib/elixir/lib/task/supervisor.ex
+++ b/lib/elixir/lib/task/supervisor.ex
@@ -53,11 +53,15 @@ defmodule Task.Supervisor do
   """
   @spec start_link([option]) :: Supervisor.on_start
   def start_link(opts \\ []) do
-    import Supervisor.Spec
     {restart, opts}  = Keyword.pop(opts, :restart, :temporary)
     {shutdown, opts} = Keyword.pop(opts, :shutdown, 5000)
-    children = [worker(Task.Supervised, [], restart: restart, shutdown: shutdown)]
-    Supervisor.start_link(children, [strategy: :simple_one_for_one] ++ opts)
+    child = %{
+      id: Task.Supervised,
+      start: {Task.Supervised, :start_link, []},
+      restart: restart,
+      shutdown: shutdown
+    }
+    Supervisor.start_link([child], [strategy: :simple_one_for_one] ++ opts)
   end
 
   @doc """
diff --git a/lib/elixir/test/elixir/supervisor_test.exs b/lib/elixir/test/elixir/supervisor_test.exs
index d52b30d21..5d5197f7a 100644
--- a/lib/elixir/test/elixir/supervisor_test.exs
+++ b/lib/elixir/test/elixir/supervisor_test.exs
@@ -6,7 +6,7 @@ defmodule SupervisorTest do
   defmodule Stack do
     use GenServer
 
-    def start_link(state, opts) do
+    def start_link({state, opts}) do
       GenServer.start_link(__MODULE__, state, opts)
     end
 
@@ -33,14 +33,11 @@ defmodule SupervisorTest do
   defmodule Stack.Sup do
     use Supervisor
 
-    def init({arg, opts}) do
-      children = [worker(Stack, [arg, opts])]
-      supervise(children, strategy: :one_for_one)
+    def init(pair) do
+      Supervisor.init([{Stack, pair}], strategy: :one_for_one)
     end
   end
 
-  import Supervisor.Spec
-
   test "generates child_spec/1" do
     assert Stack.Sup.child_spec([:hello]) == %{
       id: Stack.Sup,
@@ -51,10 +48,10 @@ defmodule SupervisorTest do
 
     defmodule CustomSup do
       use Supervisor,
-        id: :id,
-        restart: :temporary,
-        start: {:foo, :bar, []},
-        shutdown: 5000 # ignored
+          id: :id,
+          restart: :temporary,
+          start: {:foo, :bar, []},
+          shutdown: 5000 # ignored
 
       def init(arg) do
         arg
@@ -130,7 +127,7 @@ defmodule SupervisorTest do
   end
 
   test "start_link/2" do
-    children = [worker(Stack, [[:hello], [name: :dyn_stack]])]
+    children = [{Stack, {[:hello], [name: :dyn_stack]}}]
     {:ok, pid} = Supervisor.start_link(children, strategy: :one_for_one)
 
     wait_until_registered(:dyn_stack)
@@ -168,7 +165,8 @@ defmodule SupervisorTest do
     assert Supervisor.count_children(pid) ==
            %{specs: 0, active: 0, supervisors: 0, workers: 0}
 
-    {:ok, stack} = Supervisor.start_child(pid, worker(Stack, [[:hello], []]))
+    child_spec = Supervisor.child_spec({Stack, {[:hello], []}}, [])
+    {:ok, stack} = Supervisor.start_child(pid, child_spec)
     assert GenServer.call(stack, :pop) == :hello
 
     assert Supervisor.which_children(pid) ==
diff --git a/lib/ex_unit/lib/ex_unit.ex b/lib/ex_unit/lib/ex_unit.ex
index 5333d1aa4..dc28ea8f0 100644
--- a/lib/ex_unit/lib/ex_unit.ex
+++ b/lib/ex_unit/lib/ex_unit.ex
@@ -126,12 +126,10 @@ defmodule ExUnit do
 
   @doc false
   def start(_type, []) do
-    import Supervisor.Spec
-
     children = [
-      worker(ExUnit.Server, []),
-      worker(ExUnit.CaptureServer, []),
-      worker(ExUnit.OnExitHandler, [])
+      ExUnit.Server,
+      ExUnit.CaptureServer,
+      ExUnit.OnExitHandler
     ]
 
     opts = [strategy: :one_for_one, name: ExUnit.Supervisor]
diff --git a/lib/ex_unit/lib/ex_unit/capture_server.ex b/lib/ex_unit/lib/ex_unit/capture_server.ex
index ff369574d..c23cfcd50 100644
--- a/lib/ex_unit/lib/ex_unit/capture_server.ex
+++ b/lib/ex_unit/lib/ex_unit/capture_server.ex
@@ -1,27 +1,28 @@
 defmodule ExUnit.CaptureServer do
   @moduledoc false
   @timeout 30_000
+  @name __MODULE__
 
   use GenServer
 
-  def start_link() do
-    GenServer.start_link(__MODULE__, :ok, name: __MODULE__)
+  def start_link(_opts) do
+    GenServer.start_link(__MODULE__, :ok, name: @name)
   end
 
   def device_capture_on(device, pid) do
-    GenServer.call(__MODULE__, {:device_capture_on, device, pid}, @timeout)
+    GenServer.call(@name, {:device_capture_on, device, pid}, @timeout)
   end
 
   def device_capture_off(ref) do
-    GenServer.call(__MODULE__, {:device_capture_off, ref}, @timeout)
+    GenServer.call(@name, {:device_capture_off, ref}, @timeout)
   end
 
   def log_capture_on(pid) do
-    GenServer.call(__MODULE__, {:log_capture_on, pid}, @timeout)
+    GenServer.call(@name, {:log_capture_on, pid}, @timeout)
   end
 
   def log_capture_off(ref) do
-    GenServer.call(__MODULE__, {:log_capture_off, ref}, @timeout)
+    GenServer.call(@name, {:log_capture_off, ref}, @timeout)
   end
 
   ## Callbacks
diff --git a/lib/ex_unit/lib/ex_unit/event_manager.ex b/lib/ex_unit/lib/ex_unit/event_manager.ex
index 05f603495..3580bdacb 100644
--- a/lib/ex_unit/lib/ex_unit/event_manager.ex
+++ b/lib/ex_unit/lib/ex_unit/event_manager.ex
@@ -11,9 +11,12 @@ defmodule ExUnit.EventManager do
   internal statistics server for ExUnit.
   """
   def start_link() do
-    import Supervisor.Spec
-    child = worker(GenServer, [], restart: :temporary)
-    {:ok, sup} = Supervisor.start_link([child], strategy: :simple_one_for_one)
+    spec = %{
+      id: GenServer,
+      start: {GenServer, :start_link, []},
+      restart: :temporary
+    }
+    {:ok, sup} = Supervisor.start_link([spec], strategy: :simple_one_for_one)
     {:ok, event} = :gen_event.start_link()
     {:ok, {sup, event}}
   end
diff --git a/lib/ex_unit/lib/ex_unit/on_exit_handler.ex b/lib/ex_unit/lib/ex_unit/on_exit_handler.ex
index 40423bc9d..e661f99c8 100644
--- a/lib/ex_unit/lib/ex_unit/on_exit_handler.ex
+++ b/lib/ex_unit/lib/ex_unit/on_exit_handler.ex
@@ -2,7 +2,9 @@ defmodule ExUnit.OnExitHandler do
   @moduledoc false
   @name __MODULE__
 
-  def start_link do
+  use Agent
+
+  def start_link(_opts) do
     Agent.start_link(fn -> %{} end, name: @name)
   end
 
@@ -34,7 +36,7 @@ defmodule ExUnit.OnExitHandler do
       Enum.reduce(callbacks, {nil, nil, nil}, &exec_on_exit_callback(&1, timeout, &2))
 
     if is_pid(runner_pid) and Process.alive?(runner_pid) do
-      send(runner_pid, :shutdown)
+      Process.exit(runner_pid, :shutdown)
       receive do
         {:DOWN, ^runner_monitor, :process, ^runner_pid, _error} -> :ok
       end
@@ -51,8 +53,6 @@ defmodule ExUnit.OnExitHandler do
 
   defp receive_runner_reply(runner_pid, runner_monitor, state, timeout) do
     receive do
-      {^runner_pid, nil} ->
-        {runner_pid, runner_monitor, state}
       {^runner_pid, error} ->
         {runner_pid, runner_monitor, state || error}
       {:DOWN, ^runner_monitor, :process, ^runner_pid, error} ->
@@ -81,8 +81,6 @@ defmodule ExUnit.OnExitHandler do
       {:run, from, fun} ->
         send(from, {self(), exec_callback(fun)})
         on_exit_runner_loop()
-      :shutdown ->
-        :ok
     end
   end
 
diff --git a/lib/ex_unit/lib/ex_unit/server.ex b/lib/ex_unit/lib/ex_unit/server.ex
index a5f399683..228933216 100644
--- a/lib/ex_unit/lib/ex_unit/server.ex
+++ b/lib/ex_unit/lib/ex_unit/server.ex
@@ -1,32 +1,33 @@
 defmodule ExUnit.Server do
   @moduledoc false
+  @name __MODULE__
 
   use GenServer
 
-  def start_link() do
-    GenServer.start_link(__MODULE__, :ok, name: __MODULE__)
+  def start_link(_opts) do
+    GenServer.start_link(__MODULE__, :ok, name: @name)
   end
 
   def add_async_case(name) do
-    GenServer.cast(__MODULE__, {:add_async_case, name})
+    GenServer.cast(@name, {:add_async_case, name})
   end
 
   def add_sync_case(name) do
-    GenServer.cast(__MODULE__, {:add_sync_case, name})
+    GenServer.cast(@name, {:add_sync_case, name})
   end
 
   def cases_loaded do
-    GenServer.call(__MODULE__, :cases_loaded)
+    GenServer.call(@name, :cases_loaded)
   end
 
   def take_async_cases(count) do
     timeout = Application.fetch_env!(:ex_unit, :case_load_timeout)
-    GenServer.call(__MODULE__, {:take_async_cases, count}, timeout)
+    GenServer.call(@name, {:take_async_cases, count}, timeout)
   end
 
   def take_sync_cases() do
     timeout = Application.fetch_env!(:ex_unit, :case_load_timeout)
-    GenServer.call(__MODULE__, :take_sync_cases, timeout)
+    GenServer.call(@name, :take_sync_cases, timeout)
   end
 
   ## Callbacks
diff --git a/lib/iex/lib/iex/app.ex b/lib/iex/lib/iex/app.ex
index baf398702..953cc21a3 100644
--- a/lib/iex/lib/iex/app.ex
+++ b/lib/iex/lib/iex/app.ex
@@ -4,13 +4,9 @@ defmodule IEx.App do
   use Application
 
   def start(_type, _args) do
-    import Supervisor.Spec
-
-    children = [worker(IEx.Config, [])]
-    options = [strategy: :one_for_one, name: IEx.Supervisor]
-
     tab = IEx.Config.new()
-    case Supervisor.start_link(children, options) do
+
+    case Supervisor.start_link([IEx.Config], strategy: :one_for_one, name: IEx.Supervisor) do
       {:ok, pid} ->
         {:ok, pid, tab}
       {:error, _} = error ->
diff --git a/lib/iex/lib/iex/config.ex b/lib/iex/lib/iex/config.ex
index 4056dc470..721559efd 100644
--- a/lib/iex/lib/iex/config.ex
+++ b/lib/iex/lib/iex/config.ex
@@ -1,5 +1,6 @@
 defmodule IEx.Config do
   @moduledoc false
+  use Agent
 
   @table __MODULE__
   @agent __MODULE__
@@ -118,7 +119,7 @@ defmodule IEx.Config do
 
   # Agent API
 
-  def start_link() do
+  def start_link(_) do
     Agent.start_link(__MODULE__, :handle_init, [@table], [name: @agent])
   end
 
diff --git a/lib/logger/lib/logger.ex b/lib/logger/lib/logger.ex
index c0df9fada..7ac1ab1fa 100644
--- a/lib/logger/lib/logger.ex
+++ b/lib/logger/lib/logger.ex
@@ -505,7 +505,7 @@ defmodule Logger do
   @spec add_backend(atom, keyword) :: Supervisor.on_start_child
   def add_backend(backend, opts \\ []) do
     _ = if opts[:flush], do: flush()
-    case Logger.Watcher.watch(Logger, Logger.Config.translate_backend(backend), backend) do
+    case Logger.WatcherSupervisor.watch(Logger, Logger.Config.translate_backend(backend), backend) do
       {:ok, _} = ok ->
         Logger.Config.add_backend(backend)
         ok
@@ -530,7 +530,7 @@ defmodule Logger do
   def remove_backend(backend, opts \\ []) do
     _ = if opts[:flush], do: flush()
     Logger.Config.remove_backend(backend)
-    Logger.Watcher.unwatch(Logger, Logger.Config.translate_backend(backend))
+    Logger.WatcherSupervisor.unwatch(Logger, Logger.Config.translate_backend(backend))
   end
 
   @doc """
diff --git a/lib/logger/lib/logger/app.ex b/lib/logger/lib/logger/app.ex
index cd618db31..b01edfe13 100644
--- a/lib/logger/lib/logger/app.ex
+++ b/lib/logger/lib/logger/app.ex
@@ -5,25 +5,28 @@ defmodule Logger.App do
 
   @doc false
   def start(_type, _args) do
-    import Supervisor.Spec
-
     otp_reports?  = Application.get_env(:logger, :handle_otp_reports)
     sasl_reports? = Application.get_env(:logger, :handle_sasl_reports)
     threshold     = Application.get_env(:logger, :discard_threshold_for_error_logger)
+    error_handler = {:error_logger, Logger.ErrorHandler, {otp_reports?, sasl_reports?, threshold}}
 
-    options  = [strategy: :rest_for_one, name: Logger.Supervisor]
-    children = [worker(:gen_event, [{:local, Logger}]),
-                worker(Logger.Watcher, [Logger, Logger.Config, []],
-                  [id: Logger.Config, function: :watcher]),
-                supervisor(Logger.Watcher, [Logger.Config, :handlers, []]),
-                worker(Logger.Watcher,
-                  [:error_logger, Logger.ErrorHandler,
-                    {otp_reports?, sasl_reports?, threshold}],
-                  [id: Logger.ErrorHandler, function: :watcher])]
+    children = [
+      %{
+        id: :gen_event,
+        start: {:gen_event, :start_link, [{:local, Logger}]},
+        modules: :dynamic
+      },
+      {Logger.Watcher, {Logger, Logger.Config, []}},
+      {Logger.WatcherSupervisor, {Logger.Config, :handlers, []}},
+      %{
+        id: Logger.ErrorHandler,
+        start: {Logger.Watcher, :start_link, [error_handler]}
+      }
+    ]
 
     config = Logger.Config.new()
 
-    case Supervisor.start_link(children, options) do
+    case Supervisor.start_link(children, strategy: :rest_for_one, name: Logger.Supervisor) do
       {:ok, sup} ->
         handlers = [error_logger_tty_h: otp_reports?,
                     sasl_report_tty_h: sasl_reports?]
diff --git a/lib/logger/lib/logger/watcher.ex b/lib/logger/lib/logger/watcher.ex
index faf238341..45ce4e29a 100644
--- a/lib/logger/lib/logger/watcher.ex
+++ b/lib/logger/lib/logger/watcher.ex
@@ -3,53 +3,6 @@ defmodule Logger.Watcher do
 
   require Logger
   use GenServer
-  @name Logger.Watcher
-
-  @doc """
-  Starts the watcher supervisor.
-  """
-  def start_link(m, f, a) do
-    options = [strategy: :one_for_one, name: @name, max_restarts: 30, max_seconds: 3]
-    case Supervisor.start_link([], options) do
-      {:ok, _} = ok ->
-        _ = for {mod, handler, args} <- apply(m, f, a) do
-          {:ok, _} = watch(mod, handler, args)
-        end
-        ok
-      {:error, _} = error ->
-        error
-    end
-  end
-
-  @doc """
-  Removes the given handler.
-  """
-  def unwatch(mod, handler) do
-    child_id = {__MODULE__, {mod, handler}}
-    case Supervisor.terminate_child(@name, child_id) do
-      :ok ->
-         _ = Supervisor.delete_child(@name, child_id)
-        :ok
-      {:error, _} = error ->
-        error
-    end
-  end
-
-  @doc """
-  Watches the given handler as part of the watcher supervision tree.
-  """
-  def watch(mod, handler, args) do
-    import Supervisor.Spec
-    id = {__MODULE__, {mod, handler}}
-    child = worker(__MODULE__, [mod, handler, args], id: id, function: :watcher, restart: :transient)
-    case Supervisor.start_child(@name, child) do
-      {:error, :already_present} ->
-        _ = Supervisor.delete_child(@name, id)
-        watch(mod, handler, args)
-      other ->
-        other
-    end
-  end
 
   @doc """
   Starts a watcher server.
@@ -57,8 +10,8 @@ defmodule Logger.Watcher do
   This is useful when there is a need to start a handler
   outside of the handler supervision tree.
   """
-  def watcher(mod, handler, args) do
-    GenServer.start_link(__MODULE__, {mod, handler, args})
+  def start_link(triplet) do
+    GenServer.start_link(__MODULE__, triplet)
   end
 
   ## Callbacks
diff --git a/lib/logger/lib/logger/watcher_supervisor.ex b/lib/logger/lib/logger/watcher_supervisor.ex
new file mode 100644
index 000000000..1f9983eda
--- /dev/null
+++ b/lib/logger/lib/logger/watcher_supervisor.ex
@@ -0,0 +1,61 @@
+defmodule Logger.WatcherSupervisor do
+  @moduledoc false
+
+  use Supervisor
+  @name Logger.WatcherSupervisor
+
+  @doc """
+  Starts the watcher supervisor.
+  """
+  def start_link({m, f, a}) do
+    case Supervisor.start_link(__MODULE__, [], name: @name) do
+      {:ok, _} = ok ->
+        _ = for {mod, handler, args} <- apply(m, f, a) do
+          {:ok, _} = watch(mod, handler, args)
+        end
+        ok
+      {:error, _} = error ->
+        error
+    end
+  end
+
+  @doc """
+  Removes the given handler.
+  """
+  def unwatch(mod, handler) do
+    child_id = {__MODULE__, {mod, handler}}
+    case Supervisor.terminate_child(@name, child_id) do
+      :ok ->
+         _ = Supervisor.delete_child(@name, child_id)
+        :ok
+      {:error, _} = error ->
+        error
+    end
+  end
+
+  @doc """
+  Watches the given handler as part of the watcher supervision tree.
+  """
+  def watch(mod, handler, args) do
+    id = {__MODULE__, {mod, handler}}
+
+    spec = %{
+      id: id,
+      start: {Logger.Watcher, :start_link, [{mod, handler, args}]},
+      restart: :transient
+    }
+
+    case Supervisor.start_child(@name, spec) do
+      {:error, :already_present} ->
+        _ = Supervisor.delete_child(@name, id)
+        watch(mod, handler, args)
+      other ->
+        other
+    end
+  end
+
+  @doc false
+  def init(children) do
+    Supervisor.init(children, strategy: :one_for_one, max_restarts: 30, max_seconds: 3)
+  end
+end
diff --git a/lib/logger/test/logger/translator_test.exs b/lib/logger/test/logger/translator_test.exs
index 41a2ceff7..e44c76530 100644
--- a/lib/logger/test/logger/translator_test.exs
+++ b/lib/logger/test/logger/translator_test.exs
@@ -1,6 +1,5 @@
 defmodule Logger.TranslatorTest do
   use Logger.Case
-  import Supervisor.Spec
 
   defmodule MyGenServer do
     use GenServer
@@ -713,7 +712,7 @@ defmodule Logger.TranslatorTest do
     end
 
     child_opts = [restart: :temporary, function: :"start link"]
-    children = [Supervisor.Spec.worker(WeirdFunctionNamesGenServer, [], child_opts)]
+    children = [worker(WeirdFunctionNamesGenServer, [], child_opts)]
     {:ok, sup} = Supervisor.start_link(children, strategy: :simple_one_for_one)
 
     log = capture_log(:info, fn ->
@@ -769,4 +768,8 @@ defmodule Logger.TranslatorTest do
     :proc_lib.init_ack({:ok, self()})
     receive do: ({:EXIT, _, _} -> exit(:stop))
   end
+
+  defp worker(name, args, opts \\ []) do
+    Enum.into(opts, %{id: name, start: {name, opts[:function] || :start_link, args}})
+  end
 end
diff --git a/lib/mix/lib/mix.ex b/lib/mix/lib/mix.ex
index 597265d07..f9409030b 100644
--- a/lib/mix/lib/mix.ex
+++ b/lib/mix/lib/mix.ex
@@ -184,14 +184,7 @@ defmodule Mix do
 
   @doc false
   def start(_type, []) do
-    import Supervisor.Spec
-
-    children = [
-      worker(Mix.State, []),
-      worker(Mix.TasksServer, []),
-      worker(Mix.ProjectStack, [])
-    ]
-
+    children = [Mix.State, Mix.TasksServer, Mix.ProjectStack]
     opts = [strategy: :one_for_one, name: Mix.Supervisor, max_restarts: 0]
     Supervisor.start_link(children, opts)
   end
diff --git a/lib/mix/lib/mix/project_stack.ex b/lib/mix/lib/mix/project_stack.ex
index 4b761f64f..8d353c75a 100644
--- a/lib/mix/lib/mix/project_stack.ex
+++ b/lib/mix/lib/mix/project_stack.ex
@@ -1,14 +1,15 @@
 defmodule Mix.ProjectStack do
   @moduledoc false
 
+  use Agent
   @timeout 30_000
 
   @typep file    :: binary
   @typep config  :: keyword
   @typep project :: %{name: module, config: config, file: file}
 
-  @spec start_link :: {:ok, pid}
-  def start_link() do
+  @spec start_link(keyword) :: {:ok, pid}
+  def start_link(_opts) do
     initial = %{stack: [], post_config: [], cache: %{}}
     Agent.start_link fn -> initial end, name: __MODULE__
   end
@@ -72,9 +73,7 @@ defmodule Mix.ProjectStack do
     end
   end
 
-  @doc """
-  Runs the given function in the recursing root.
-  """
+  @spec root((() -> result)) :: result when result: var
   def root(fun) do
     {top, file} =
       get_and_update fn %{stack: stack} = state ->
@@ -121,11 +120,7 @@ defmodule Mix.ProjectStack do
     end
   end
 
-  @doc """
-  Enables the recursion for the project at the top of the stack
-  during the given function.
-  """
-  @spec recur((... -> result)) :: result when result: var
+  @spec recur((() -> result)) :: result when result: var
   def recur(fun) do
     cast fn %{stack: [h | t]} = state ->
       %{state | stack: [%{h | recursing?: true} | t]}
@@ -140,11 +135,6 @@ defmodule Mix.ProjectStack do
     end
   end
 
-  @doc """
-  Returns the module that started the recursion.
-
-  Returns nil if not recursive.
-  """
   @spec recursing :: module | nil
   def recursing do
     get fn %{stack: stack} ->
diff --git a/lib/mix/lib/mix/state.ex b/lib/mix/lib/mix/state.ex
index 906ef5758..8e6095625 100644
--- a/lib/mix/lib/mix/state.ex
+++ b/lib/mix/lib/mix/state.ex
@@ -2,7 +2,9 @@ defmodule Mix.State do
   @moduledoc false
   @name __MODULE__
 
-  def start_link() do
+  use Agent
+
+  def start_link(_opts) do
     Agent.start_link(__MODULE__, :init, [], [name: @name])
   end
 
diff --git a/lib/mix/lib/mix/tasks/new.ex b/lib/mix/lib/mix/tasks/new.ex
index a6beb5482..d90b8093d 100644
--- a/lib/mix/lib/mix/tasks/new.ex
+++ b/lib/mix/lib/mix/tasks/new.ex
@@ -424,12 +424,10 @@ defmodule Mix.Tasks.New do
     use Application
 
     def start(_type, _args) do
-      import Supervisor.Spec, warn: false
-
-      # Define workers and child supervisors to be supervised
+      # List all child processes to be supervised
       children = [
-        # Starts a worker by calling: <%= @mod %>.Worker.start_link(arg1, arg2, arg3)
-        # worker(<%= @mod %>.Worker, [arg1, arg2, arg3]),
+        # Starts a worker by calling: <%= @mod %>.Worker.start_link(arg)
+        # {<%= @mod %>.Worker, arg},
       ]
 
       # See https://hexdocs.pm/elixir/Supervisor.html
diff --git a/lib/mix/lib/mix/tasks_server.ex b/lib/mix/lib/mix/tasks_server.ex
index 3ca82b584..5efc4ea72 100644
--- a/lib/mix/lib/mix/tasks_server.ex
+++ b/lib/mix/lib/mix/tasks_server.ex
@@ -1,7 +1,9 @@
 defmodule Mix.TasksServer do
   @moduledoc false
 
-  def start_link() do
+  use Agent
+
+  def start_link(_opts) do
     Agent.start_link(fn -> %{} end, name: __MODULE__)
   end