Fix dialyzer warnings in support code

This also runs Dialyzer in the test environment so that the support code
is checked from now on. Credo was moved for consistency.

Author: Frank Hunleth

mix.exs

@@ -16,7 +16,13 @@ defmodule Delux.MixProject do
       docs: docs(),
       dialyzer: dialyzer(),
       deps: deps(),
-      preferred_cli_env: %{docs: :docs, "hex.build": :docs, "hex.publish": :docs}
+      preferred_cli_env: %{
+        docs: :docs,
+        "hex.build": :docs,
+        "hex.publish": :docs,
+        credo: :test,
+        dialyzer: :test
+      }
     ]
   end
 
@@ -32,8 +38,8 @@ defmodule Delux.MixProject do
   defp deps do
     [
       {:ex_doc, "~> 0.22", only: :docs, runtime: false},
-      {:dialyxir, "~> 1.1", only: :dev, runtime: false},
-      {:credo, "~> 1.5", only: :dev, runtime: false}
+      {:dialyxir, "~> 1.1", only: :test, runtime: false},
+      {:credo, "~> 1.5", only: :test, runtime: false}
     ]
   end
 

test/delux/backend_test.exs

@@ -48,8 +48,8 @@ defmodule Delux.BackendTest do
     assert FakeLEDs.read_trigger(2) == "none"
 
     assert FakeLEDs.read_pattern(0) == "255 500 255 0 0 500 0 0 "
-    assert FakeLEDs.read_pattern(1) == ""
-    assert FakeLEDs.read_pattern(2) == ""
+    assert FakeLEDs.read_pattern(1) == :eof
+    assert FakeLEDs.read_pattern(2) == :eof
   end
 
   @tag :tmp_dir

test/delux_test.exs

@@ -97,7 +97,7 @@ defmodule DeluxTest do
     # Set a lower priority blink and check that nothing gets written
     Delux.render(pid, Delux.Effects.blink(:green, 5), :status)
     assert info_as_binary(pid) == "green at 1 Hz"
-    assert FakeLEDs.read_pattern(0) == ""
+    assert FakeLEDs.read_pattern(0) == :eof
 
     # Clear the higher priority blink
     Delux.render(pid, nil, :notification)
@@ -167,17 +167,17 @@ defmodule DeluxTest do
     assert FakeLEDs.read_pattern(1) == "0 3600000 0 0 "
     assert FakeLEDs.read_pattern(2) == "1 250 1 0 0 250 0 0 "
     # Not written
-    assert FakeLEDs.read_pattern(3) == ""
-    assert FakeLEDs.read_pattern(4) == ""
-    assert FakeLEDs.read_pattern(5) == ""
+    assert FakeLEDs.read_pattern(3) == :eof
+    assert FakeLEDs.read_pattern(4) == :eof
+    assert FakeLEDs.read_pattern(5) == :eof
 
     # Start a second blink on indicator2
     Delux.render(pid, %{indicator2: Delux.Effects.blink(:blue, 1)}, :status)
     assert info_as_binary(pid) == "magenta at 2 Hz"
     assert info_as_binary(pid, :indicator2) == "blue at 1 Hz"
-    assert FakeLEDs.read_pattern(0) == ""
-    assert FakeLEDs.read_pattern(1) == ""
-    assert FakeLEDs.read_pattern(2) == ""
+    assert FakeLEDs.read_pattern(0) == :eof
+    assert FakeLEDs.read_pattern(1) == :eof
+    assert FakeLEDs.read_pattern(2) == :eof
     assert FakeLEDs.read_pattern(3) == "0 3600000 0 0 "
     assert FakeLEDs.read_pattern(4) == "0 3600000 0 0 "
     assert FakeLEDs.read_pattern(5) == "1 500 1 0 0 500 0 0 "
@@ -189,18 +189,18 @@ defmodule DeluxTest do
     assert FakeLEDs.read_pattern(0) == "0 3600000 0 0 "
     assert FakeLEDs.read_pattern(1) == "0 3600000 0 0 "
     assert FakeLEDs.read_pattern(2) == "0 3600000 0 0 "
-    assert FakeLEDs.read_pattern(3) == ""
-    assert FakeLEDs.read_pattern(4) == ""
-    assert FakeLEDs.read_pattern(5) == ""
+    assert FakeLEDs.read_pattern(3) == :eof
+    assert FakeLEDs.read_pattern(4) == :eof
+    assert FakeLEDs.read_pattern(5) == :eof
 
     # Turn off the second blink
     Delux.render(pid, %{indicator2: nil}, :status)
     assert info_as_binary(pid) == "off"
     assert info_as_binary(pid, :indicator2) == "off"
 
-    assert FakeLEDs.read_pattern(0) == ""
-    assert FakeLEDs.read_pattern(1) == ""
-    assert FakeLEDs.read_pattern(2) == ""
+    assert FakeLEDs.read_pattern(0) == :eof
+    assert FakeLEDs.read_pattern(1) == :eof
+    assert FakeLEDs.read_pattern(2) == :eof
     assert FakeLEDs.read_pattern(3) == "0 3600000 0 0 "
     assert FakeLEDs.read_pattern(4) == "0 3600000 0 0 "
     assert FakeLEDs.read_pattern(5) == "0 3600000 0 0 "

test/support/fake_leds.ex

@@ -17,15 +17,17 @@ defmodule Delux.Support.FakeLEDs do
 
     Process.put({__MODULE__, :led_dir}, led_dir)
 
-    for i <- 0..5 do
+    Enum.each(0..5, fn i ->
       File.mkdir_p!(base_dir(led_dir, i))
       File.write!(trigger_path(led_dir, i), "none")
       File.write!(max_brightness_path(led_dir, i), "#{max_brightness}")
       File.write!(pattern_path(led_dir, i), "")
 
       handle = File.open!(pattern_path(led_dir, i), [:read, :raw])
       Process.put({__MODULE__, i}, handle)
-    end
+    end)
+
+    :ok
   end
 
   @spec read_trigger(non_neg_integer()) :: binary()
@@ -34,13 +36,32 @@ defmodule Delux.Support.FakeLEDs do
     File.read!(trigger_path(led_dir, index))
   end
 
-  @spec read_pattern(non_neg_integer()) :: binary()
+  @spec read_pattern(non_neg_integer()) :: binary() | :eof | {:error, any()}
   def read_pattern(index) do
     # This is a little tricky since tests must read the pattern
     # after every time it's set. This is due to how the backend code
     # to Linux just keeps appending to the magic file to set patterns,
     # but our simulation doesn't truncate the file after every write.
     handle = Process.get({__MODULE__, index})
-    IO.binread(handle, :all)
+    binread(handle)
+  end
+
+  if Version.match?(System.version(), "~> 1.13") do
+    defp binread(handle) do
+      case IO.binread(handle, :eof) do
+        :eof -> :eof
+        {:error, _} = error -> error
+        data -> IO.iodata_to_binary(data)
+      end
+    end
+  else
+    # Elixir 1.12 and earlier use :all and return empty strings
+    defp binread(handle) do
+      case IO.binread(handle, :all) do
+        "" -> :eof
+        {:error, _} = error -> error
+        data -> IO.iodata_to_binary(data)
+      end
+    end
   end
 end