Expose fs as an option to override the default implementations

README.md

@@ -178,6 +178,8 @@ Otherwise, undefined variables will cause an exception. Defaults to `false`.
 
 * `greedy` is used to specify whether `trim*Left`/`trim*Right` is greedy. When set to `true`, all consecutive blank characters including `\n` will be trimed regardless of line breaks. Defaults to `true`.
 
+* `fs` is used to override the default file-system module with a custom implementation.
+
 ## Register Filters
 
 ```javascript

src/liquid-options.ts

@@ -1,4 +1,5 @@
 import * as _ from './util/underscore'
+import IFS from './fs/ifs';
 
 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 `["."]` */
@@ -28,7 +29,9 @@ export interface LiquidOptions {
   outputDelimiterLeft?: string,
   outputDelimiterRight?: string,
   /** `greedy` is used to specify whether `trim*Left`/`trim*Right` is greedy. When set to `true`, all consecutive blank characters including `\n` will be trimed regardless of line breaks. Defaults to `true`. */
-  greedy?: boolean
+  greedy?: boolean,
+  /** `fs` is used to override the default file-system module with a custom implementation */
+  fs?: IFS
 }
 
 interface NormalizedOptions extends LiquidOptions {

src/liquid.ts

@@ -15,19 +15,22 @@ import builtinTags from './builtin/tags'
 import builtinFilters from './builtin/filters'
 import { LiquidOptions, NormalizedFullOptions, applyDefault, normalize } from './liquid-options'
 import { FilterImplOptions } from './template/filter/filter-impl-options'
+import IFS from './fs/ifs';
 
 export default class Liquid {
   public options: NormalizedFullOptions
   public renderer: Render
   public parser: Parser
   private cache: object = {}
   private tokenizer: Tokenizer
+  private fs: IFS
 
   constructor (opts: LiquidOptions = {}) {
     this.options = applyDefault(normalize(opts))
     this.parser = new Parser(this)
     this.renderer = new Render()
     this.tokenizer = new Tokenizer(this.options)
+    this.fs = opts.fs || fs
 
     _.forOwn(builtinTags, (conf, name) => this.registerTag(name, conf))
     _.forOwn(builtinFilters, (handler, name) => this.registerFilter(name, handler))
@@ -48,14 +51,14 @@ export default class Liquid {
   async getTemplate (file: string, opts?: LiquidOptions) {
     const options = normalize(opts)
     const roots = options.root ? [...options.root, ...this.options.root] : this.options.root
-    const paths = roots.map(root => fs.resolve(root, file, this.options.extname))
+    const paths = roots.map(root => this.fs.resolve(root, file, this.options.extname))
 
     for (const filepath of paths) {
       if (this.options.cache && this.cache[filepath]) return this.cache[filepath]
 
-      if (!(await fs.exists(filepath))) continue
+      if (!(await this.fs.exists(filepath))) continue
 
-      const value = this.parse(await fs.readFile(filepath), filepath)
+      const value = this.parse(await this.fs.readFile(filepath), filepath)
       if (this.options.cache) this.cache[filepath] = value
       return value
     }

test/integration/liquid/fs-option.ts

@@ -0,0 +1,21 @@
+import { expect } from 'chai'
+import Liquid from '../../../src/liquid'
+
+describe('LiquidOptions#fs', function () {
+  let engine: Liquid
+  const fs = {
+    exists: () => Promise.resolve(true),
+    readFile: () => Promise.resolve('test file content'),
+    resolve: () => 'resolved'
+  }
+  beforeEach(function () {
+    engine = new Liquid({
+      root: '/root/',
+      fs
+    })
+  })
+  it('should be used to read templates', function () {
+    return engine.renderFile('files/foo')
+      .then(x => expect(x).to.equal('test file content'))
+  })
+})