Fixed unit tests

When patches are unapplied, getting the beam file returned an empty
path charlist, which dialyzer assumed was a real file name due to a
weak assumption, which caused unit tests to fail. This was remedied by
checking for a non-empty charlist, which allows tests to succeed.

Also made patch a test only dependency for .formatter.exs, as this was
causing formatters to fail.

Author: scohen

apps/language_server/.formatter.exs

@@ -3,6 +3,13 @@ impossible_to_format = [
   "test/fixtures/project_with_tests/test/error_test.exs"
 ]
 
+deps =
+  if Mix.env() == :test do
+    [:patch]
+  else
+    []
+  end
+
 proto_dsl = [
   defalias: 1,
   defenum: 1,
@@ -14,7 +21,7 @@ proto_dsl = [
 ]
 
 [
-  import_deps: [:patch],
+  import_deps: deps,
   export: [
     locals_without_parens: proto_dsl
   ],

apps/language_server/lib/language_server/dialyzer/utils.ex

@@ -4,13 +4,14 @@ defmodule ElixirLS.LanguageServer.Dialyzer.Utils do
   @spec dialyzable?(module()) :: boolean()
   def dialyzable?(module) do
     file = get_beam_file(module)
+
     is_list(file) and match?({:ok, _}, :dialyzer_utils.get_core_from_beam(file))
   end
 
   @spec get_beam_file(module()) :: charlist() | :preloaded | :non_existing | :cover_compiled
   def get_beam_file(module) do
     case :code.which(module) do
-      file when is_list(file) ->
+      [_ | _] = file ->
         file
 
       other ->

apps/language_server/test/experimental/project_test.exs

@@ -137,6 +137,7 @@ defmodule ElixirLS.Experimental.ProjectTest do
 
   def with_patched_system_put_env(_) do
     patch(System, :put_env, :ok)
+    on_exit(fn -> restore(System) end)
     :ok
   end
 

apps/language_server/test/experimental/server/configuration_test.exs

@@ -149,6 +149,11 @@ defmodule ElixirLS.Experimental.Server.ConfigurationTest do
 
   def with_patched_system_put_env(_) do
     patch(System, :put_env, :ok)
+
+    on_exit(fn ->
+      restore(System)
+    end)
+
     :ok
   end