Move configuration to module

Summary:
Moves the JSON config access to one module instead of
ad-hoc de-serialising the object all over the place.
This also adds a type for it so we hopefully won't typo things that easily.

Reviewed By: danielbuechele

Differential Revision: D13956612

fbshipit-source-id: 48098deafedf18cc86c8802a3c40fba9394b8262

src/utils/__tests__/processConfig.node.js

@@ -0,0 +1,42 @@
+/**
+ * Copyright 2018-present Facebook.
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ * @format
+ */
+
+import {default as config, resetConfigForTesting} from '../processConfig.js';
+
+afterEach(() => {
+  resetConfigForTesting();
+});
+
+test('config is decoded from env', () => {
+  process.env.CONFIG = JSON.stringify({
+    disabledPlugins: ['pluginA', 'pluginB', 'pluginC'],
+    pluginPaths: ['/a/path', 'b/path'],
+    lastWindowPosition: {x: 4, y: 8, width: 15, height: 16},
+    updaterEnabled: false,
+    screenCapturePath: '/my/screenshot/path',
+  });
+
+  expect(config()).toEqual({
+    disabledPlugins: new Set(['pluginA', 'pluginB', 'pluginC']),
+    pluginPaths: ['/a/path', 'b/path'],
+    lastWindowPosition: {x: 4, y: 8, width: 15, height: 16},
+    updaterEnabled: false,
+    screenCapturePath: '/my/screenshot/path',
+  });
+});
+
+test('config is decoded from env with defaults', () => {
+  process.env.CONFIG = '{}';
+
+  expect(config()).toEqual({
+    disabledPlugins: new Set([]),
+    pluginPaths: [],
+    lastWindowPosition: undefined,
+    updaterEnabled: true,
+    screenCapturePath: undefined,
+  });
+});