Use system environment when {:system, ...} is set

lib/exquickbooks.ex

@@ -31,9 +31,12 @@ defmodule ExQuickBooks do
   """
   def backend do
     case get_env(@backend_config) do
-      backend when is_atom(backend) -> backend
-      nil                           -> raise_missing(@backend_config)
-      _                             -> raise_invalid(@backend_config)
+      backend when is_atom(backend) ->
+        backend
+      nil ->
+        raise_missing(@backend_config)
+      other ->
+        raise_invalid(@backend_config, other)
     end
   end
 
@@ -42,9 +45,12 @@ defmodule ExQuickBooks do
   """
   def callback_url do
     case get_env(@callback_config) do
-      url when is_binary(url) -> url
-      nil                     -> raise_missing(@callback_config)
-      _                       -> raise_invalid(@callback_config)
+      url when is_binary(url) ->
+        url
+      nil ->
+        raise_missing(@callback_config)
+      other ->
+        raise_invalid(@callback_config, other)
     end
   end
 
@@ -54,22 +60,34 @@ defmodule ExQuickBooks do
   def credentials do
     for k <- @credential_config do
       case get_env(k) do
-        v when is_binary(v) -> {k, v}
-        nil                 -> raise_missing(k)
-        _                   -> raise_invalid(k)
+        v when is_binary(v) ->
+          {k, v}
+        nil ->
+          raise_missing(k)
+        v ->
+          raise_invalid(k, v)
       end
     end
   end
 
+  # Returns a value from the application's environment. If the value matches
+  # the {:system, ...} syntax, a system environment variable will be retrieved
+  # instead and parsed.
   defp get_env(key, default \\ nil) do
-    Application.get_env(:exquickbooks, key, default)
+    with {:system, var} <- Application.get_env(:exquickbooks, key, default) do
+      case System.get_env(var) do
+        "true"  -> true
+        "false" -> false
+         value  -> value
+      end
+    end
   end
 
   defp raise_missing(key) do
     raise "ExQuickBooks configuration value '#{key}' is required."
   end
 
-  defp raise_invalid(key) do
-    raise "ExQuickBooks configuration value '#{key}' is invalid."
+  defp raise_invalid(key, value) do
+    raise "ExQuickBooks configuration value '#{key}' is invalid, got: #{value}"
   end
 end

test/exquickbooks_test.exs

@@ -5,9 +5,11 @@ defmodule ExQuickBooksTest do
 
   setup do
     old_env = get_all_env()
+    old_system_env = System.get_env
 
     on_exit fn ->
       restore_env(old_env)
+      restore_system_env(old_system_env)
     end
   end
 
@@ -16,14 +18,14 @@ defmodule ExQuickBooksTest do
   end
 
   test "accounting_api/0 returns the sandbox URL by default" do
-    delete_env(:use_production_api)
+    delete_env :use_production_api
 
     assert ExQuickBooks.accounting_api |> String.starts_with?("https")
     assert ExQuickBooks.accounting_api |> String.contains?("sandbox")
   end
 
   test "accounting_api/0 returns the production URL in production" do
-    put_env(:use_production_api, true)
+    put_env :use_production_api, true
 
     assert ExQuickBooks.accounting_api |> String.starts_with?("https")
     refute ExQuickBooks.accounting_api |> String.contains?("sandbox")
@@ -35,8 +37,8 @@ defmodule ExQuickBooksTest do
   end
 
   test "credentials/0 returns the right credentials" do
-    put_env(:consumer_key, "key")
-    put_env(:consumer_secret, "secret")
+    put_env :consumer_key, "key"
+    put_env :consumer_secret, "secret"
 
     assert ExQuickBooks.credentials == [
       consumer_key: "key",
@@ -45,19 +47,39 @@ defmodule ExQuickBooksTest do
   end
 
   test "credentials/0 raises for missing credentials" do
-    delete_env(:consumer_key)
-    delete_env(:consumer_secret)
+    delete_env :consumer_key
+    delete_env :consumer_secret
 
     assert_raise RuntimeError, &ExQuickBooks.credentials/0
   end
 
   test "credentials/0 raises for invalid credentials" do
-    put_env(:consumer_key, 42)
-    put_env(:consumer_secret, 42)
+    put_env :consumer_key, 42
+    put_env :consumer_secret, 42
 
     assert_raise RuntimeError, &ExQuickBooks.credentials/0
   end
 
+  test "{:system, ...} syntax is supported" do
+    System.put_env %{
+      "EXQUICKBOOKS_KEY" => "system_key",
+      "EXQUICKBOOKS_SECRET" => "system_secret",
+      "EXQUICKBOOKS_USE_PRODUCTION_API" => "true"
+    }
+
+    put_env :consumer_key, {:system, "EXQUICKBOOKS_KEY"}
+    put_env :consumer_secret, {:system, "EXQUICKBOOKS_SECRET"}
+    put_env :use_production_api, {:system, "EXQUICKBOOKS_USE_PRODUCTION_API"}
+
+    assert ExQuickBooks.credentials == [
+      consumer_key: "system_key",
+      consumer_secret: "system_secret"
+    ]
+
+    # Production config flag should be parsed as a boolean
+    refute ExQuickBooks.accounting_api |> String.contains?("sandbox")
+  end
+
   defp get_all_env do
     Application.get_all_env(:exquickbooks)
   end
@@ -82,4 +104,17 @@ defmodule ExQuickBooksTest do
     `async: false`.
     """
   end
+
+  defp restore_system_env(old_env) do
+    new_env = System.get_env
+
+    for {k, _} <- new_env, do: System.delete_env(k)
+    for {k, v} <- old_env, do: System.put_env(k, v)
+
+    System.get_env == old_env || raise """
+    Could not restore the system's environment. Check that you're not modifying
+    it simultaneously in other tests. Those tests should specify
+    `async: false`.
+    """
+  end
 end