feat: export toPromise and toValue, see #158

src/liquid.ts

@@ -14,7 +14,7 @@ import { FilterMap } from './template/filter/filter-map'
 import { LiquidOptions, normalizeStringArray, NormalizedFullOptions, applyDefault, normalize } from './liquid-options'
 import { FilterImplOptions } from './template/filter/filter-impl-options'
 import { FS } from './fs/fs'
-import { toThenable, toValue } from './util/async'
+import { toPromise, toValue } from './util/async'
 
 export * from './types'
 
@@ -49,7 +49,7 @@ export class Liquid {
     return this.renderer.renderTemplates(tpl, ctx)
   }
   public async render (tpl: Template[], scope?: object, opts?: LiquidOptions): Promise<string> {
-    return toThenable(this._render(tpl, scope, opts, false))
+    return toPromise(this._render(tpl, scope, opts, false))
   }
   public renderSync (tpl: Template[], scope?: object, opts?: LiquidOptions): string {
     return toValue(this._render(tpl, scope, opts, true))
@@ -60,7 +60,7 @@ export class Liquid {
     return this._render(tpl, scope, opts, sync)
   }
   public async parseAndRender (html: string, scope?: object, opts?: LiquidOptions): Promise<string> {
-    return toThenable(this._parseAndRender(html, scope, opts, false))
+    return toPromise(this._parseAndRender(html, scope, opts, false))
   }
   public parseAndRenderSync (html: string, scope?: object, opts?: LiquidOptions): string {
     return toValue(this._parseAndRender(html, scope, opts, true))
@@ -88,7 +88,7 @@ export class Liquid {
     throw this.lookupError(file, options.root)
   }
   public async parseFile (file: string, opts?: LiquidOptions): Promise<Template[]> {
-    return toThenable(this._parseFile(file, opts, false))
+    return toPromise(this._parseFile(file, opts, false))
   }
   public parseFileSync (file: string, opts?: LiquidOptions): Template[] {
     return toValue(this._parseFile(file, opts, true))
@@ -108,7 +108,7 @@ export class Liquid {
     return value.value(ctx)
   }
   public async evalValue (str: string, ctx: Context): Promise<any> {
-    return toThenable(this._evalValue(str, ctx))
+    return toPromise(this._evalValue(str, ctx))
   }
   public evalValueSync (str: string, ctx: Context): any {
     return toValue(this._evalValue(str, ctx))

src/template/tag/hash.ts

@@ -21,7 +21,7 @@ export class Hash {
   * render (ctx: Context) {
     const hash = {}
     for (const key of Object.keys(this.hash)) {
-      hash[key] = evalToken(this.hash[key], ctx)
+      hash[key] = yield evalToken(this.hash[key], ctx)
     }
     return hash
   }

src/types.ts

@@ -17,3 +17,4 @@ export { TopLevelToken } from './tokens/toplevel-token'
 export { Tokenizer } from './parser/tokenizer'
 export { Hash } from './template/tag/hash'
 export { evalToken, evalQuotedToken } from './render/expression'
+export { toPromise, toThenable, toValue } from './util/async'

src/util/async.ts

@@ -7,7 +7,7 @@ interface Thenable {
   catch (reject: resolver): Thenable;
 }
 
-function mkResolve (value: any) {
+function createResolvedThenable (value: any): Thenable {
   const ret = {
     then: (resolve: resolver) => resolve(value),
     catch: () => ret
@@ -15,7 +15,7 @@ function mkResolve (value: any) {
   return ret
 }
 
-function mkReject (err: Error) {
+function createRejectedThenable (err: Error): Thenable {
   const ret = {
     then: (resolve: resolver, reject?: resolver) => {
       if (reject) return reject(err)
@@ -30,43 +30,49 @@ function isThenable (val: any): val is Thenable {
   return val && isFunction(val.then)
 }
 
-function isCustomIterable (val: any): val is IterableIterator<any> {
+function isAsyncIterator (val: any): val is IterableIterator<any> {
   return val && isFunction(val.next) && isFunction(val.throw) && isFunction(val.return)
 }
 
+// convert an async iterator to a thenable (Promise compatible)
 export function toThenable (val: IterableIterator<any> | Thenable | any): Thenable {
   if (isThenable(val)) return val
-  if (isCustomIterable(val)) return reduce()
-  return mkResolve(val)
+  if (isAsyncIterator(val)) return reduce()
+  return createResolvedThenable(val)
 
   function reduce (prev?: any): Thenable {
     let state
     try {
       state = (val as IterableIterator<any>).next(prev)
     } catch (err) {
-      return mkReject(err)
+      return createRejectedThenable(err)
     }
 
-    if (state.done) return mkResolve(state.value)
+    if (state.done) return createResolvedThenable(state.value)
     return toThenable(state.value!).then(reduce, err => {
       let state
       try {
         state = (val as IterableIterator<any>).throw!(err)
       } catch (e) {
-        return mkReject(e)
+        return createRejectedThenable(e)
       }
-      if (state.done) return mkResolve(state.value)
+      if (state.done) return createResolvedThenable(state.value)
       return reduce(state.value)
     })
   }
 }
 
+export function toPromise (val: IterableIterator<any> | Thenable | any): Promise<any> {
+  return Promise.resolve(toThenable(val))
+}
+
+// get the value of async iterator in synchronous manner
 export function toValue (val: IterableIterator<any> | Thenable | any) {
   let ret: any
   toThenable(val)
     .then((x: any) => {
       ret = x
-      return mkResolve(ret)
+      return createResolvedThenable(ret)
     })
     .catch((err: Error) => {
       throw err

test/unit/util/async.ts

@@ -1,10 +1,19 @@
-import { toThenable, toValue } from '../../../src/util/async'
+import { toThenable, toPromise, toValue } from '../../../src/util/async'
 import { expect, use } from 'chai'
 import * as chaiAsPromised from 'chai-as-promised'
 
 use(chaiAsPromised)
 
 describe('utils/async', () => {
+  describe('#toPromise()', function () {
+    it('should return a promise', async () => {
+      function * foo () {
+        return 'foo'
+      }
+      const result = await toPromise(foo())
+      expect(result).to.equal('foo')
+    })
+  })
   describe('#toThenable()', function () {
     it('should support iterable with single return statement', async () => {
       function * foo () {