Issue #19294 has been reported by zverok (Victor Shepelev). ---------------------------------------- Bug #19294: Enumerator.product works incorrectly with consuming enumerators https://bugs.ruby-lang.org/issues/19294 * Author: zverok (Victor Shepelev) * Status: Open * Priority: Normal * Backport: 2.7: UNKNOWN, 3.0: UNKNOWN, 3.1: UNKNOWN, 3.2: UNKNOWN ---------------------------------------- ```ruby s = StringIO.new('abc') Enumerator.product([1, 2, 3], s.each_char).to_a # Expected: => [[1, "a"], [1, "b"], [1, "c"], [2, "a"], [2, "b"], [2, "c"], [3, "a"], [3, "b"], [3, "c"]] # Actual: => [[1, "a"], [1, "b"], [1, "c"]] ``` The implementation consumes the non-first enumerator to produce the first combination. Somewhat related to the dilemma of consuming and non-consuming enumerators (#19061). PS: I noticed I don't understand why it is `Enumerator.product` and not `Enumerable#product`, but probably it is too late to raise the questions :( -- https://bugs.ruby-lang.org/