Empty string wrongly translated to '0'

[Chouby]

I encountered a case where an empty string is translated to '0', when I expected it to be ''. This edge case is due to the translation file having the string '0', translated to '0'.

According to the PHP documentation ​https://www.php.net/manual/en/language.types.array.php, in array keys,

• null is the same as ''
• false and '0' are the same as 0

In Translation_Entry::key() we can find:

<?php
if ( null === $this->singular || '' === $this->singular ) {
        return false;
}

The singular string being the key of the entries array, that means that null, '', false, 0 and '0' all have the same translation.
I don't expect non-string keys to be used, but '' and '0' are two valid strings which should accept different translations.

[Chouby]

• null is the same as
• false and '0' are the same as 0

Sorry, I messed with formatting and don't know how to edit the ticket. This must be read:

• null is the same as ''
• false and '0' are the same as 0

[audrasjb]

Thanks chouby, the reported issue looks legitimate to me.
Definitely moving this for 6.1 consideration.

[audrasjb]

@Chouby you can edit the ticket at the bottom of this page, just use the "description" field :)

[manooweb]

Replying to audrasjb:

@Chouby you can edit the ticket at the bottom of this page, just use the "description" field :)<

Are you sure? I also didn't see this field on one of my tickets.

[rafiahmedd]

I think we can return just an empty string instead of false because false return a value 0 and that's why an empty string turns into 0 instead of ''.

Trac ticket: https://core.trac.wordpress.org/ticket/55941

• Do not return false when calling key() on an empty string translation entry.
• Add test accordingly.

[lopo]

I'm reviewing this one as part of the Yoast Contributor Day activities.
The patch looks good to me and appears to be working as expected.

To test the fix I:

• changed a string in the Settings page to '' (empty string)
• switched my env to Italian
• added the following to admin-it_IT.po and updated the .mo with msgfmt on the command line

  msgid "0"
  msgstr "0"
  

• I could see the empty string was wrongly translated as 0
• applying the patch the string is correctly translated to an empty string.

[audrasjb]

Thanks for the patch @lopo, it works fine on my side using your test scenario. Thanks for adding some unit tests, too.

Self-assigning for commit.

[audrasjb]

In 54315:

i18n: Ensure empty strings are consistently translated to ''.

This changeset fixes an edge case where empty strings were wrongly translated to '0' (falsey value) instead of '' (empty string).

Props Chouby, manooweb, rafiahmedd, lopo.
Fixes #55941.

Committed in https://core.trac.wordpress.org/changeset/54315

[audrasjb]

I forgot @hugod in the props list, so I'm adding them with the manual Props tool located in the Make/Core website. Sorry for the inconvenience.

[audrasjb]

Mistake solved :)