Bug #17216: Enumerator::Chain doesn't support all Enumerator methods

• Status: Closed
• Priority: Normal
• Assignee: -
• Target version: -
• ruby -v: ruby 2.7.1p83 (2020-03-31 revision a0c7c23c9c) [x86_64-darwin19]
• Backport: 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN

[jeremie (Jérémie Laval)]

Despite the fact that Enumerator::Chain (returned by Enumerator#chain) is supposed to inherit from Enumerator, a lot of Enumerator methods do not work on a chain instance throwing the following error:

TypeError (wrong argument type chain (expected enumerator))

The following code exhibit the problem:

[1, 2, 3].chain([4, 5, 6]).with_index.to_a

A workaround is to use each (also work with map, to_enum, and others) to force a conversion back to a plain enumerator which seems superfluous:

[1, 2, 3].chain([4, 5, 6]).each.with_index.to_a

[jeremyevans0 (Jeremy Evans)]

I agree that calling the methods directly should work. I've submitted a pull request to internally wrap the Enumerator::Chain in an Enumerator so it doesn't raise TypeError: https://github.com/ruby/ruby/pull/3811

[nobu (Nobuyoshi Nakada)]

• Has duplicate Feature #17347: Enumerator::Chain of Enumerator::Lazy should be lazy added

• Status changed from Open to Closed

Applied in changeset git|bf40fe9fed19a5e22081b133661c0629988f1618.

---

Fix calling enumerator methods such as with_index on Enumerator::Chain

This previously raised a TypeError. Wrap the Enumerator::Chain in
an Enumerator to work around the problem.

Fixes [Bug #17216]