fix: map filter allow nil results in strict mode, fixes #647

src/context/context.ts

@@ -76,11 +76,11 @@ export class Context {
   public getFromScope (scope: unknown, paths: PropertyKey[] | string): IterableIterator<unknown> {
     return toValueSync(this._getFromScope(scope, paths))
   }
-  public * _getFromScope (scope: unknown, paths: PropertyKey[] | string): IterableIterator<unknown> {
+  public * _getFromScope (scope: unknown, paths: PropertyKey[] | string, strictVariables = this.strictVariables): IterableIterator<unknown> {
     if (isString(paths)) paths = paths.split('.')
     for (let i = 0; i < paths.length; i++) {
       scope = yield readProperty(scope as object, paths[i], this.ownPropertyOnly)
-      if (this.strictVariables && isUndefined(scope)) {
+      if (strictVariables && isUndefined(scope)) {
         throw new InternalUndefinedVariableError((paths as string[]).slice(0, i + 1).join!('.'))
       }
     }

src/filters/array.ts

@@ -38,7 +38,7 @@ export const size = (v: string | any[]) => (v && v.length) || 0
 export function * map (this: FilterImpl, arr: Scope[], property: string): IterableIterator<unknown> {
   const results = []
   for (const item of toArray(toValue(arr))) {
-    results.push(yield this.context._getFromScope(item, stringify(property).split('.')))
+    results.push(yield this.context._getFromScope(item, stringify(property), false))
   }
   return results
 }

src/template/filter.spec.ts

@@ -31,7 +31,10 @@ describe('filter', function () {
   it('should render a simple filter', async function () {
     expect(await toPromise(new Filter('upcase', (x: string) => x.toUpperCase(), [], liquid).render('foo', ctx))).toBe('FOO')
   })
-
+  it('should reject promise when filter throws', async function () {
+    const filter = new Filter('foo', function * () { throw new Error('intended') }, [], liquid)
+    expect(toPromise(filter.render('foo', ctx))).rejects.toMatch('intended')
+  })
   it('should render filters with argument', async function () {
     const two = new NumberToken('2', 0, 1, undefined)
     expect(await toPromise(new Filter('add', (a: number, b: number) => a + b, [two], liquid).render(3, ctx))).toBe(5)

src/template/filter.ts

@@ -27,6 +27,6 @@ export class Filter {
       if (isKeyValuePair(arg)) argv.push([arg[0], yield evalToken(arg[1], context)])
       else argv.push(yield evalToken(arg, context))
     }
-    return this.handler.apply({ context, liquid: this.liquid }, [value, ...argv])
+    return yield this.handler.apply({ context, liquid: this.liquid }, [value, ...argv])
   }
 }

test/integration/filters/array.spec.ts

@@ -58,6 +58,14 @@ describe('filters/array', function () {
       const post = { category: 'foo' }
       return test('{{post | map: "category"}}', { post }, 'foo')
     })
+    it('should allow nil results in strictVariables mode', function () {
+      const engine = new Liquid({ strictVariables: true })
+      const ctx = {
+        posts: [{ category: 'foo' }, { title: 'bar' }]
+      }
+      const result = engine.parseAndRenderSync('{{posts | map: "category" | json}}', ctx)
+      expect(result).toEqual('["foo",null]')
+    })
     it('should support nested property', function () {
       const tpl = '{{ arr | map: "name.first" | join }}'
       const a = { name: { first: 'Alice' } }