feat: orderedFilterParameters, closes #312

Author: Harttle

src/builtin/tags/for.ts

@@ -3,14 +3,18 @@ import { toEnumerable } from '../../util/collection'
 import { ForloopDrop } from '../../drop/forloop-drop'
 import { Hash } from '../../template/tag/hash'
 
+const MODIFIERS = ['offset', 'limit', 'reversed']
+
+type valueof<T> = T[keyof T]
+
 export default {
   type: 'block',
   parse: function (token: TagToken, remainTokens: TopLevelToken[]) {
-    const toknenizer = new Tokenizer(token.args, this.liquid.options.operatorsTrie)
+    const tokenizer = new Tokenizer(token.args, this.liquid.options.operatorsTrie)
 
-    const variable = toknenizer.readIdentifier()
-    const inStr = toknenizer.readIdentifier()
-    const collection = toknenizer.readValue()
+    const variable = tokenizer.readIdentifier()
+    const inStr = tokenizer.readIdentifier()
+    const collection = tokenizer.readValue()
     assert(
       variable.size() && inStr.content === 'in' && collection,
       () => `illegal tag: ${token.getText()}`
@@ -44,14 +48,15 @@ export default {
     }
 
     const hash = yield this.hash.render(ctx)
-    const offset = hash.offset || 0
-    const limit = (hash.limit === undefined) ? collection.length : hash.limit
-    const reversedIndex = Reflect.ownKeys(hash).indexOf('reversed')
+    const modifiers = this.liquid.options.orderedFilterParameters
+      ? Object.keys(hash).filter(x => MODIFIERS.includes(x))
+      : MODIFIERS.filter(x => hash[x] !== undefined)
 
-    // reverse collection before slicing if 'reversed' is 1st parameter
-    if (reversedIndex === 0) collection.reverse()
-    collection = collection.slice(offset, offset + limit)
-    if (reversedIndex > 0) collection.reverse()
+    collection = modifiers.reduce((collection, modifier: valueof<typeof MODIFIERS>) => {
+      if (modifier === 'offset') return offset(collection, hash['offset'])
+      if (modifier === 'limit') return limit(collection, hash['limit'])
+      return reversed(collection)
+    }, collection)
 
     const scope = { forloop: new ForloopDrop(collection.length) }
     ctx.push(scope)
@@ -68,3 +73,15 @@ export default {
     ctx.pop()
   }
 } as TagImplOptions
+
+function reversed<T> (arr: Array<T>) {
+  return [...arr].reverse()
+}
+
+function offset<T> (arr: Array<T>, count: number) {
+  return arr.slice(count)
+}
+
+function limit<T> (arr: Array<T>, count: number) {
+  return arr.slice(0, count)
+}

src/liquid-options.ts

@@ -55,6 +55,8 @@ export interface LiquidOptions {
   keepOutputType?: boolean;
   /** An object of operators for conditional statements. Defaults to the regular Liquid operators. */
   operators?: Operators;
+  /** Respect parameter order when using filters like "for ... reversed limit", Defaults to `false`. */
+  orderedFilterParameters?: boolean;
 }
 
 interface NormalizedOptions extends LiquidOptions {

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] = yield evalToken(this.hash[key], ctx)
+      hash[key] = this.hash[key] === undefined ? true : yield evalToken(this.hash[key], ctx)
     }
     return hash
   }

test/integration/builtin/tags/for.ts

@@ -215,6 +215,13 @@ describe('tags/for', function () {
     })
 
     it('should support for reversed in the first position', async function () {
+      const src = '{% for i in (1..8) reversed limit:2 %}{{ i }}{% endfor %}'
+      const html = await liquid.parseAndRender(src, scope)
+      return expect(html).to.equal('21')
+    })
+
+    it('should support for reversed in the first position with orderedFilterParameters=true', async function () {
+      const liquid = new Liquid({ orderedFilterParameters: true })
       const src = '{% for i in (1..8) reversed limit:2 %}{{ i }}{% endfor %}'
       const html = await liquid.parseAndRender(src, scope)
       return expect(html).to.equal('87')
@@ -225,6 +232,13 @@ describe('tags/for', function () {
       const html = await liquid.parseAndRender(src)
       return expect(html).to.equal('543')
     })
+
+    it('should support for reversed in the middle position with orderedFilterParameters=true', async function () {
+      const liquid = new Liquid({ orderedFilterParameters: true })
+      const src = '{% for i in (1..8) offset:2 reversed limit:3 %}{{ i }}{% endfor %}'
+      const html = await liquid.parseAndRender(src)
+      return expect(html).to.equal('876')
+    })
   })
 
   describe('sync', function () {

test/unit/template/hash.ts

@@ -9,7 +9,7 @@ describe('Hash', function () {
   it('should parse "reverse"', async function () {
     const hash = await toThenable(new Hash('reverse').render(new Context({ foo: 3 })))
     expect(hash).to.haveOwnProperty('reverse')
-    expect(hash.reverse).to.be.undefined
+    expect(hash.reverse).to.be.true
   })
   it('should parse "num:foo"', async function () {
     const hash = await toThenable(new Hash('num:foo').render(new Context({ foo: 3 })))
@@ -37,7 +37,7 @@ describe('Hash', function () {
     const hash = await toThenable(new Hash('num1:2.3 reverse,num2:bar.coo\n num3: arr[0]').render(ctx))
     expect(hash).to.deep.equal({
       num1: 2.3,
-      reverse: undefined,
+      reverse: true,
       num2: 3,
       num3: 4
     })