Add script for picking random files for formatting

2 files changed, 62 insertions, 1 deletions

diff --git a/.formatter.exs b/.formatter.exs
index fa6844b64..57b824457 100644
--- a/.formatter.exs
+++ b/.formatter.exs
@@ -1,4 +1,9 @@
 [
+  inputs: [
+    "lib/*/{lib,unicode,test}/**/*.{ex,exs}",
+    "lib/*/mix.exs"
+  ],
+
   locals_without_parens: [
     # Formatter tests
     assert_format: 2,
@@ -9,4 +14,4 @@
     # Mix tests
     in_tmp: 2
   ]
-]
\ No newline at end of file
+]
diff --git a/scripts/random_file.exs b/scripts/random_file.exs
new file mode 100644
index 000000000..b60b72ee9
--- /dev/null
+++ b/scripts/random_file.exs
@@ -0,0 +1,56 @@
+# bin/elixir scripts/random_file.exs
+
+defmodule RandomFile do
+  @pattern "lib/*/{lib,unicode,test}/**/*.{ex,exs}"
+
+  def run(args) do
+    popper =
+      if "--alphabetically" in args do
+        &Enum.split(&1, 1)
+      else
+        fn collection ->
+          random = Enum.random(collection)
+          {random, List.delete(collection, random)}
+        end
+      end
+
+    {opts, _} = Code.eval_file(".formatter.exs")
+
+    @pattern
+    |> Path.wildcard()
+    |> random_file(popper, opts)
+  end
+
+  defp random_file([], _popper, _opts) do
+    IO.puts("All files are formatted, hooray!")
+  end
+
+  defp random_file(collection, popper, opts) do
+    {file, collection} = popper.(collection)
+
+    IO.write("Checking #{file}... ")
+    input = File.read!(file)
+    output = IO.iodata_to_binary([Code.format_string!(file, opts), ?\n])
+
+    if input == output do
+      IO.puts("already formatted.")
+      random_file(collection, popper, opts)
+    else
+      IO.write("""
+      jackpot!
+
+      The file above needs formatting.
+      Please format it with the command below:
+
+          bin/elixir bin/mix format #{file}
+
+      Once formatted, check for any faults and submit a pull request.
+      For more information see: https://github.com/elixir-lang/elixir/issues/6643
+
+      Have fun!
+      """)
+    end
+  end
+end
+
+RandomFile.run(System.argv())