Support for additional environment variables. (#622)

* add support for adding environment variables

* update restart message

* check for nil map, not necesarily always a map

Author: vacarsu

apps/language_server/lib/language_server/server.ex

@@ -1097,12 +1097,14 @@ defmodule ElixirLS.LanguageServer.Server do
     enable_dialyzer =
       Dialyzer.check_support() == :ok && Map.get(settings, "dialyzerEnabled", true)
 
+    env_vars = Map.get(settings, "envVariables")
     mix_env = Map.get(settings, "mixEnv", "test")
     mix_target = Map.get(settings, "mixTarget")
     project_dir = Map.get(settings, "projectDir")
 
     state =
       state
+      |> maybe_set_env_vars(env_vars)
       |> set_mix_env(mix_env)
       |> maybe_set_mix_target(mix_target)
       |> set_project_dir(project_dir)
@@ -1127,6 +1129,20 @@ defmodule ElixirLS.LanguageServer.Server do
     end
   end
 
+  defp maybe_set_env_vars(state = %__MODULE__{}, nil), do: state
+
+  defp maybe_set_env_vars(state = %__MODULE__{}, env) do
+    prev_env = state.settings["envVariables"]
+
+    if is_nil(prev_env) or env == prev_env do
+      System.put_env(env)
+    else
+      JsonRpc.show_message(:warning, "You must restart ElixirLS after changing environment variables")
+    end
+
+    state
+  end
+
   defp set_mix_env(state = %__MODULE__{}, env) do
     prev_env = state.settings["mixEnv"]