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Bug #79927

Generator doesn't throw exception after multiple yield from iterable

Submitted:

2020-08-03 21:14 UTC

Modified:

2020-10-11 00:08 UTC

Votes:	2
Avg. Score:	3.5 ± 0.5
Reproduced:	2 of 2 (100.0%)
Same Version:	0 (0.0%)
Same OS:	1 (50.0%)

From:

roxblnfk at yandex dot com

Assigned:

nikic (profile)

Status:

Closed

Package:

Scripting Engine problem

PHP Version:

7.4.8

OS:

any

Private report:

CVE-ID:

None

View Developer Edit

[2020-08-03 21:14 UTC] roxblnfk at yandex dot com

Description:
------------
A generator that yields values from an array does not throw an exception when calling the rewind method after multiple yields from same yield construction.

Can also be seen at https://3v4l.org/NZ77U

Test script:
---------------
<?php

$generator = (static function () {
    yield from [1,2,3];
})();

$generator->next();
$generator->next();
$generator->rewind();
echo $generator->current(); # 3

Expected result:
----------------
RuntimeException on line $generator->rewind();

Actual result:
--------------
3

Patches

Pull Requests

History

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[2020-08-11 13:49 UTC] [email protected]

Automatic comment on behalf of [email protected]
Revision: http://git.php.net/?p=php-src.git;a=commit;h=e25aab64268adb4e233737c274b195e1662f7211
Log: Fixed bug #79927

[2020-08-11 13:49 UTC] [email protected]

-Status: Open +Status: Closed

[2020-10-10 21:15 UTC] roxblnfk at ya dot ru

Do i understand correctly that this bug will not be fixed for php 7?

[2020-10-11 00:08 UTC] [email protected]

-Assigned To: +Assigned To: requinix

[2020-10-11 00:08 UTC] [email protected]

That's right. Because it would not be polite if code that already runs in 7.4 suddenly started throwing exceptions with the next release.

[2020-10-11 00:08 UTC] [email protected]

-Assigned To: requinix +Assigned To: nikic

[2020-10-11 14:24 UTC] roxblnfk at yandex dot com

I think those who wrote the generator rewind code did it with the behavior described in the documentation.
I wrote the code too, expecting and considering that the generator would throw an exception. The incorrect behavior was found only during testing.
I, of course, do not insist, but think that it is worth releasing a fix for php7 and writing a warning in the patch note.

Now php7 does not work as it is written in the documentation regarding Generator::rewind()

[2020-10-19 11:07 UTC] sam at rmcreative dot ru

I think it should be fixed in PHP 7 as well:

1. It contradicts documentation.
2. There's no way to work around it.

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