wip: non-interrupting watcher working

lib/mix/tasks/mneme.watch.ex

@@ -0,0 +1,11 @@
+defmodule Mix.Tasks.Mneme.Watch do
+  @shortdoc "Re-runs tests on save, interrupting Mneme prompts"
+  @moduledoc """
+  TODO
+  """
+
+  use Mix.Task
+
+  @impl Mix.Task
+  defdelegate run(args), to: Mneme.Watch
+end

lib/mneme.ex

@@ -364,6 +364,8 @@ defmodule Mneme do
   """
   @doc section: :setup
   def start(opts \\ []) do
+    maybe_reenable_ansi()
+
     opts =
       if Keyword.has_key?(opts, :restart) do
         [
@@ -389,6 +391,12 @@ defmodule Mneme do
     :ok
   end
 
+  defp maybe_reenable_ansi do
+    if System.get_env("MIX_MNEME_WATCH") == "true" do
+      Application.put_env(:elixir, :ansi_enabled, true)
+    end
+  end
+
   defp start_server! do
     children = [
       Mneme.Server

lib/mneme/watch.ex

@@ -0,0 +1,117 @@
+defmodule Mneme.Watch do
+  @moduledoc false
+
+  use GenServer
+
+  @doc """
+  Runs `mix.test` with the given CLI arguments, restarting when files change.
+  """
+  @spec run([String.t()]) :: no_return()
+  def run(args \\ []) do
+    Mix.env(:test)
+    ensure_os!()
+
+    :ok = Application.ensure_started(:file_system)
+
+    children = [
+      {__MODULE__, cli_args: args}
+    ]
+
+    Supervisor.start_link(children, strategy: :one_for_one)
+
+    :timer.sleep(:infinity)
+  end
+
+  @doc false
+  def start_link(opts) do
+    GenServer.start_link(__MODULE__, opts, name: __MODULE__)
+  end
+
+  @impl GenServer
+  def init(opts) do
+    Code.compiler_options(ignore_module_conflict: true)
+
+    state = opts |> Keyword.validate!([:cli_args]) |> Map.new()
+    file_system_opts = [dirs: [File.cwd!()], name: :mneme_file_system_watcher]
+
+    case FileSystem.start_link(file_system_opts) do
+      {:ok, _} ->
+        FileSystem.subscribe(:mneme_file_system_watcher)
+        {:ok, state, {:continue, :first_run}}
+
+      other ->
+        other
+    end
+  end
+
+  @impl GenServer
+  def handle_continue(:first_run, state) do
+    Mix.Task.run(:test, state.cli_args)
+    flush()
+
+    {:noreply, state}
+  end
+
+  @impl GenServer
+  def handle_info({:file_event, _pid, {path, _events}}, state) do
+    path = Path.relative_to_cwd(path)
+
+    if watching?(path) do
+      IO.puts("detected change: #{path}")
+      run_tests(state.cli_args)
+      flush()
+    end
+
+    {:noreply, state}
+  end
+
+  defp watching?(path) do
+    watching_directory?(path) and watching_extension?(path)
+  end
+
+  defp watching_directory?(path) do
+    ignored = ~w(deps/ _build/ .lexical/ .elixir_ls/ .elixir-tools/)
+    not String.starts_with?(path, ignored)
+  end
+
+  defp watching_extension?(path) do
+    watching = ~w(.erl .ex .exs .eex .leex .heex .xrl .yrl .hrl)
+    Path.extname(path) in watching
+  end
+
+  defp run_tests(cli_args) do
+    Code.unrequire_files(Code.required_files())
+    IEx.Helpers.recompile()
+    Mix.Task.reenable(:test)
+    Mix.Task.run(:test, cli_args)
+  end
+
+  defp flush do
+    receive do
+      _ -> flush()
+    after
+      0 -> :ok
+    end
+  end
+
+  defp ensure_os! do
+    case os_type() do
+      :unix ->
+        :ok
+
+      unsupported ->
+        error = "file watcher is unsupported on OS: #{inspect(unsupported)}"
+
+        [:red, "error: ", :default_color, error]
+        |> IO.ANSI.format()
+        |> then(&IO.puts(:stderr, &1))
+
+        System.halt(1)
+    end
+  end
+
+  defp os_type do
+    {os_type, _} = :os.type()
+    os_type
+  end
+end

mix.exs

@@ -41,6 +41,7 @@ defmodule Mneme.MixProject do
       {:nimble_options, "~> 1.0"},
       {:sourceror, "~> 1.0"},
       {:rewrite, "~> 0.10.1"},
+      {:file_system, "~> 1.0"},
 
       # Development / Test
       {:benchee, "~> 1.0", only: :dev},
@@ -83,7 +84,8 @@ defmodule Mneme.MixProject do
       dialyzer: :test,
       coveralls: :test,
       "coveralls.html": :test,
-      "test.mneme_not_started": :test
+      "test.mneme_not_started": :test,
+      "mneme.watch": :test
     ]
   end
 

mix.lock

@@ -8,6 +8,7 @@
   "erlex": {:hex, :erlex, "0.2.6", "c7987d15e899c7a2f34f5420d2a2ea0d659682c06ac607572df55a43753aa12e", [:mix], [], "hexpm", "2ed2e25711feb44d52b17d2780eabf998452f6efda104877a3881c2f8c0c0c75"},
   "ex_doc": {:hex, :ex_doc, "0.34.1", "9751a0419bc15bc7580c73fde506b17b07f6402a1e5243be9e0f05a68c723368", [:mix], [{:earmark_parser, "~> 1.4.39", [hex: :earmark_parser, repo: "hexpm", optional: false]}, {:makeup_c, ">= 0.1.0", [hex: :makeup_c, repo: "hexpm", optional: true]}, {:makeup_elixir, "~> 0.14 or ~> 1.0", [hex: :makeup_elixir, repo: "hexpm", optional: false]}, {:makeup_erlang, "~> 0.1 or ~> 1.0", [hex: :makeup_erlang, repo: "hexpm", optional: false]}, {:makeup_html, ">= 0.1.0", [hex: :makeup_html, repo: "hexpm", optional: true]}], "hexpm", "d441f1a86a235f59088978eff870de2e815e290e44a8bd976fe5d64470a4c9d2"},
   "excoveralls": {:hex, :excoveralls, "0.18.1", "a6f547570c6b24ec13f122a5634833a063aec49218f6fff27de9df693a15588c", [:mix], [{:castore, "~> 1.0", [hex: :castore, repo: "hexpm", optional: true]}, {:jason, "~> 1.0", [hex: :jason, repo: "hexpm", optional: false]}], "hexpm", "d65f79db146bb20399f23046015974de0079668b9abb2f5aac074d078da60b8d"},
+  "file_system": {:hex, :file_system, "1.0.0", "b689cc7dcee665f774de94b5a832e578bd7963c8e637ef940cd44327db7de2cd", [:mix], [], "hexpm", "6752092d66aec5a10e662aefeed8ddb9531d79db0bc145bb8c40325ca1d8536d"},
   "glob_ex": {:hex, :glob_ex, "0.1.7", "eae6b6377147fb712ac45b360e6dbba00346689a87f996672fe07e97d70597b1", [:mix], [], "hexpm", "decc1c21c0c73df3c9c994412716345c1692477b9470e337f628a7e08da0da6a"},
   "jason": {:hex, :jason, "1.4.0", "e855647bc964a44e2f67df589ccf49105ae039d4179db7f6271dfd3843dc27e6", [:mix], [{:decimal, "~> 1.0 or ~> 2.0", [hex: :decimal, repo: "hexpm", optional: true]}], "hexpm", "79a3791085b2a0f743ca04cec0f7be26443738779d09302e01318f97bdb82121"},
   "makeup": {:hex, :makeup, "1.1.2", "9ba8837913bdf757787e71c1581c21f9d2455f4dd04cfca785c70bbfff1a76a3", [:mix], [{:nimble_parsec, "~> 1.2.2 or ~> 1.3", [hex: :nimble_parsec, repo: "hexpm", optional: false]}], "hexpm", "cce1566b81fbcbd21eca8ffe808f33b221f9eee2cbc7a1706fc3da9ff18e6cac"},

test/mneme/example_test.exs

@@ -24,7 +24,7 @@ defmodule Mneme.ExampleTest do
   end
 
   test "2" do
-    s2 = %MyStruct{field: 5}
+    s2 = %MyStruct{field: 1}
 
     auto_assert %MyStruct{field: 5, list: [:foo, :buzz]} <-
                   %{