Bug #77587 [Opn->Nab]: Inconsistent behaviour when returning generators

Edit report at https://bugs.php.net/bug.php?id=77587&edit=1 ID: 77587 Updated by: nikic@php.net Reported by: adamnicholson10 at gmail dot com Summary: Inconsistent behaviour when returning generators -Status: Open +Status: Not a bug Type: Bug Package: *General Issues Operating System: Linux PHP Version: Irrelevant Block user comment: N Private report: N New Comment: return foo() is just that: You are returning a generator object. What you are looking for is "yield from foo()". See also http://php.net/manual/en/language.generators.syntax.php#control-structures.yield.from Previous Comments: ------------------------------------------------------------------------ [2019-02-08 12:03:57] adamnicholson10 at gmail dot com Description: ------------ There appears to be inconsistent behaviour when returning generators. Given the function foo() returns a generator, when you consume that generator in a new function which also returns a generator, you would expect return foo() to have the same behaviour as looping over the values of foo() and performing a yield on each value; however this doesn't appear to be the case if the function you are consuming foo() contains other yield statements. It looks like PHP is getting confused by having both yield statements, and return $generator statements, in the same function body. This appears to affect all PHP versions tested which support generators POC (code below): https://3v4l.org/e86mK Test script: --------------- <?php function generator() { foreach ([1, 2, 3, 4, 5] as $i) { yield $i; } } function A(): \Generator { return generator(); } function B(): \Generator { if (false) { yield 7; return; } return generator(); } function C(): \Generator { if (false) { yield 7; return; } foreach (generator() as $i) { yield $i; } } echo "-A\n"; foreach (A() as $i) { echo "{$i}\n"; } echo "-B\n"; foreach (B() as $i) { echo "{$i}\n"; } echo "-C\n"; foreach (C() as $i) { echo "{$i}\n"; } echo "Done\n"; Expected result: ---------------- -A 1 2 3 4 5 -B 1 2 3 4 5 -C 1 2 3 4 5 Done Actual result: -------------- -A 1 2 3 4 5 -B -C 1 2 3 4 5 Done ------------------------------------------------------------------------ -- Edit this bug report at https://bugs.php.net/bug.php?id=77587&edit=1