fix: for tag not respecting Drop#valueOf(), fixes #515

test/integration/builtin/tags/for.ts

@@ -324,8 +324,7 @@ describe('tags/for', function () {
         yield 'b'
         yield 'c'
       }
-
-      public valueOf (): string {
+      toString () {
         return 'MockIterableDrop'
       }
     }

test/integration/drop/drop.ts

@@ -61,4 +61,15 @@ describe('drop/drop', function () {
     const html = await liquid.parseAndRender(`{{obj.foo}}`, { obj: new PromiseDrop() })
     expect(html).to.equal('FOO')
   })
+  it('should respect valueOf', async () => {
+    class CustomDrop extends Drop {
+      prop = 'not enumerable'
+      valueOf () {
+        return ['foo', 'bar']
+      }
+    }
+    const tpl = '{{drop}}: {% for field in drop %}{{ field }};{% endfor %}'
+    const html = await liquid.parseAndRender(tpl, { drop: new CustomDrop() })
+    expect(html).to.equal('foobar: foo;bar;')
+  })
 })

test/unit/drop/drop.ts

@@ -1,10 +0,0 @@
-import { expect } from 'chai'
-import { Drop } from '../../../src/drop/drop'
-
-describe('drop/drop', function () {
-  class CustomDrop extends Drop { }
-
-  it('.valueOf() should return undefined by default', async function () {
-    expect(new CustomDrop().valueOf()).to.be.undefined
-  })
-})