Stricter undefined checks for options

Author: blakeembrey

src/index.ts

@@ -55,8 +55,8 @@ export const VERSION = pkg.version
  * Registration options.
  */
 export interface Options {
-  typeCheck?: boolean | null
-  cache?: boolean | null
+  typeCheck?: boolean
+  cache?: boolean
   cacheDirectory?: string
   compiler?: string
   project?: boolean | string
@@ -169,9 +169,9 @@ export function register (options: Options = {}): Register {
   ).concat(emptyFileListWarnings).map(Number)
   const getFile = options.getFile || DEFAULTS.getFile
   const fileExists = options.fileExists || DEFAULTS.fileExists
-  const shouldCache = !!(options.cache == null ? DEFAULTS.cache : options.cache)
-  const typeCheck = !!(options.typeCheck == null ? DEFAULTS.typeCheck : options.typeCheck)
-  const project = options.project == null ? DEFAULTS.project : options.project
+  const shouldCache = !!(options.cache === undefined ? DEFAULTS.cache : options.cache)
+  const typeCheck = !!(options.typeCheck === undefined ? DEFAULTS.typeCheck : options.typeCheck)
+  const project = options.project === undefined ? DEFAULTS.project : options.project
   const cacheDirectory = options.cacheDirectory || DEFAULTS.cacheDirectory || getTmpDir()
   const compilerOptions = Object.assign({}, DEFAULTS.compilerOptions, options.compilerOptions)
   const originalJsHandler = require.extensions['.js']