refactor: remove mock-fs from dev dependency

src/liquid-options.ts

@@ -1,3 +1,5 @@
+import * as _ from './util/underscore'
+
 export interface LiquidOptions {
   /** `root` is a directory or an array of directories to resolve layouts and includes, as well as the filename passed in when calling `.renderFile()`. If an array, the files are looked up in the order they occur in the array. Defaults to `["."]` */
   root?: string | string[]
@@ -23,7 +25,11 @@ export interface LiquidOptions {
   greedy?: boolean
 }
 
-export const defaultOptions: LiquidOptions = {
+export interface NormalizedOptions extends LiquidOptions {
+  root?: string[]
+}
+
+export const defaultOptions: NormalizedOptions = {
   root: ['.'],
   cache: false,
   extname: '',
@@ -36,3 +42,17 @@ export const defaultOptions: LiquidOptions = {
   strict_filters: false,
   strict_variables: false
 }
+
+export function normalize (options: LiquidOptions): NormalizedOptions {
+  options = options || {}
+  if (options.hasOwnProperty('root')) {
+    options.root = normalizeStringArray(options.root)
+  }
+  return options as NormalizedOptions
+}
+
+function normalizeStringArray (value: string | string[]): string[] {
+  if (_.isArray(value)) return value as string[]
+  if (_.isString(value)) return [value as string]
+  return []
+}