Bug #17113: /\K/ in separator for String#split behaves differently than /(?<=)/

• Status: Closed
• Assignee: -
• Target version: -
• ruby -v: ruby 2.8.0dev (2020-08-11T07:51:07Z master 5af983af4f) [x86_64-linux]
• Backport: 2.5: REQUIRED, 2.6: REQUIRED, 2.7: REQUIRED

[hanazuki (Kasumi Hanazuki)]

When a String is #splitted with a pattern containing /\K/ (lookbehind) operator,
the portion that matches the lookbehind pattern will not appear in the result.

"abcd".split(/b\Kc/)  # => ["a", "d"]
"abcd".split(/(?<=b)c/)  # => ["ab", "d"] -- expected result

In this example, since /b\Kc/ matches "c" in "abcd", the result is expected to be ["ab", "d"]. Actually ["a", "d"] is returned.
(?<=) operator seems to work expectedly.

[hanazuki (Kasumi Hanazuki)]

Patch: https://github.com/ruby/ruby/pull/3407

[hanazuki (Kasumi Hanazuki)]

• Status changed from Open to Closed

Applied in changeset git|e79cdcf61b0665d8a9bb309a607227de43e95673.

---

string.c(rb_str_split_m): Handle /\K/ correctly

Use BEG(0) instead of the result of rb_reg_search to handle the cases
when the separator Regexp contains /\K/ (lookbehind) operator.

Fixes [Bug #17113]

[nobu (Nobuyoshi Nakada)]

• Backport changed from 2.5: UNKNOWN, 2.6: UNKNOWN, 2.7: UNKNOWN to 2.5: REQUIRED, 2.6: REQUIRED, 2.7: REQUIRED