Fix dialyzer warnings and test race condition

Author: kipcole9

lib/image_ocr/input.ex

@@ -54,10 +54,9 @@ defmodule ImageOcr.Input do
   end
 
   def to_vimage(charlist) when is_list(charlist) do
-    case List.to_string(charlist) do
-      path when is_binary(path) -> to_vimage(path)
-      _ -> {:error, {:unsupported_input, :invalid_charlist}}
-    end
+    to_vimage(List.to_string(charlist))
+  rescue
+    ArgumentError -> {:error, {:unsupported_input, :invalid_charlist}}
   end
 
   def to_vimage(other), do: {:error, {:unsupported_input, other}}

mix.exs

@@ -18,6 +18,7 @@ defmodule ImageOcr.MixProject do
       description: description(),
       package: package(),
       docs: docs(),
+      dialyzer: dialyzer(),
       source_url: @source_url
     ]
   end
@@ -56,6 +57,16 @@ defmodule ImageOcr.MixProject do
     ]
   end
 
+  defp dialyzer do
+    [
+      # The mix tasks under lib/mix/tasks/ legitimately call Mix.Task.run/1,
+      # Mix.shell/0, and Mix.raise/1 — pull :mix into the PLT so dialyzer
+      # can see those callbacks. :inets / :public_key are used by the
+      # tessdata HTTP fetcher.
+      plt_add_apps: [:mix, :inets, :ssl, :public_key, :ex_unit]
+    ]
+  end
+
   defp docs do
     [
       main: "readme",

test/image_ocr/concurrency_test.exs

@@ -59,8 +59,12 @@ defmodule ImageOcr.ConcurrencyTest do
   end
 
   test "instance is garbage-collected without crashing the VM" do
+    # Pass :datapath explicitly so this test is not sensitive to other test
+    # modules transiently mutating the :tessdata_path application env.
+    datapath = ImageOcr.Tessdata.vendored_path()
+
     Enum.each(1..50, fn _ ->
-      {:ok, _ocr} = ImageOcr.new()
+      {:ok, _ocr} = ImageOcr.new(datapath: datapath)
     end)
 
     :erlang.garbage_collect()

test/image_ocr/tessdata_test.exs

@@ -1,5 +1,8 @@
 defmodule ImageOcr.TessdataTest do
-  use ExUnit.Case, async: true
+  # async: false because these tests mutate Application env / OS env
+  # (`:image_ocr, :tessdata_path` and `TESSDATA_PREFIX`), which is global
+  # state that would otherwise race ImageOcr.new/1 calls in other modules.
+  use ExUnit.Case, async: false
 
   alias ImageOcr.Tessdata