Allow setting a literal false for configuration properties (#1585)

Author: gj

package/utils/__tests__/deep_assign.js

@@ -2,10 +2,31 @@
 
 const deepAssign = require('../deep_assign')
 
-test('deep assign property', () => {
-  const object = { foo: { bar: { } } }
-  const path = 'foo.bar'
-  const value = { x: 1, y: 2 }
-  const expectation = { foo: { bar: { x: 1, y: 2 } } }
-  expect(deepAssign(object, path, value)).toEqual(expectation)
+describe('deepAssign()', () => {
+  test('deeply assigns nested properties', () => {
+    const object = { foo: { bar: { } } }
+    const path = 'foo.bar'
+    const value = { x: 1, y: 2 }
+    const expectation = { foo: { bar: { x: 1, y: 2 } } }
+    expect(deepAssign(object, path, value)).toEqual(expectation)
+  })
+
+  test('allows assignment of a literal false', () => {
+    const object = { foo: { bar: { } } }
+    const path = 'foo.bar'
+    const value = false
+    const expectation = { foo: { bar: false } }
+    expect(deepAssign(object, path, value)).toEqual(expectation)
+  })
+
+  test('does not allow assignment of other falsy values', () => {
+    const object = { foo: { bar: { } } }
+    const path = 'foo.bar'
+    const values = [undefined, null, 0, '']
+
+    values.forEach(value => {
+      const expectation = new Error(`Value can't be ${value}`)
+      expect(() => deepAssign(object, path, value)).toThrow(expectation)
+    })
+  })
 })

package/utils/deep_assign.js

@@ -2,7 +2,7 @@ const { canMerge, prettyPrint } = require('./helpers')
 const deepMerge = require('./deep_merge')
 
 const deepAssign = (obj, path, value) => {
-  if (!value) throw new Error(`Value can't be ${value}`)
+  if (!value && value !== false) throw new Error(`Value can't be ${value}`)
 
   const keys = path.split('.')
   const key = keys.pop()