Language suggestor on the beta plugin repository is incorrect

[Clorith]

The language suggestor on the rest of WordPress.org suggest Danish, Norwegian (Bokmål) and Swedish, which are appropriate given me being in Norway and the headers I send.

Accepted-Language header
en-US,en;q=0.8,da;q=0.6,nb;q=0.4,sv;q=0.2
Hitting up the page from 79.160.197.135 in case GeoIP is kicking in and doing strange things.

Tested with the Yoast SEO plugin at ​https://wordpress.org/plugins-wp/wordpress-seo/ and being suggested Bulgarian (Български)

[Otto42]

The beta repo doesn't have a custom language suggester, yet.

[ocean90]

@Otto42 It has: https://meta.trac.wordpress.org/browser/sites/trunk/wordpress.org/public_html/wp-content/plugins/plugin-directory/api/routes/class-locale-banner.php

[Otto42]

Ahh, okay then. That's different than what I was looking for.

[SergeyBiryukov]

Confirmed:

accept-language: en-US,en;q=0.8,ru;q=0.6,cs;q=0.4

Results in: "This plugin is also available in ​Български (also: ​Русский)".

[SergeyBiryukov]

Traced the issue to two bugs in Locale_Banner class:

1. In Locale_Banner::locale_banner()​, $suggest_locales is an array intersection between locales based on the HTTP Accept-Language header and all available locales. However, due to $locales_from_header being the second argument, the order of preference is defined by the list of all locales (which appears to be randomly returned from DB) instead of the locales provided by Accept-Language header. As a result, the primary language is determined incorrectly (in my case, Russian should be the first, but only comes second).
2. In Locale_Banner::map_locale()​, if an exact match is not found (e.g. when trying to map cs_CS to cs_CZ), an attempt is made to omit the region and only compare the language part. However, what it actually does is return the first non-empty locale from the list of all available locales, which happens to be bg_BG.

meta-1850.patch​ addresses both issues. Here's some debug info before the patch:

$http_locales: Array ( [0] => en-US [1] => en [2] => ru [3] => cs ) 
$lang: ru, $region: RU
$mapped: ru_RU
$lang: cs, $region: CS
$mapped: bg_BG
$translated_locales: Array ( [0] => bg_BG [1] => uk [2] => fr_FR [3] => tr_TR [4] => de_DE [5] => ru_RU [6] => cs_CZ ) 
$locales_from_header: Array ( [0] => ru_RU [1] => bg_BG ) 
array_intersect: Array ( [0] => bg_BG [5] => ru_RU ) 
$suggest_locales: Array ( [0] => bg_BG [1] => ru_RU ) 
$suggest_named_locales: Array ( [bg_BG] => Bulgarian [ru_RU] => Russian ) 

and after:

$http_locales: Array ( [0] => en-US [1] => en [2] => ru [3] => cs ) 
$lang: ru, $region: RU
$mapped: ru_RU
$lang: cs, $region: CS
$mapped: cs_CZ
$translated_locales: Array ( [0] => bg_BG [1] => uk [2] => fr_FR [3] => tr_TR [4] => de_DE [5] => ru_RU [6] => cs_CZ ) 
$locales_from_header: Array ( [0] => ru_RU [1] => cs_CZ ) 
array_intersect: Array ( [0] => ru_RU [1] => cs_CZ ) 
$suggest_locales: Array ( [0] => ru_RU [1] => cs_CZ ) 
$suggest_named_locales: Array ( [ru_RU] => Russian [cs_CZ] => Czech ) 

[ocean90]

Thanks @SergeyBiryukov. We should add some unit tests for that.

[SergeyBiryukov]

Replying to ocean90:

We should add some unit tests for that.

Yep, I was working on a test. See meta-1850.2.patch​.

[ocean90]

In 5008:

Plugin Directory: Fix two incorrect cases when trying to match a HTTP header to a WordPress locale.

Includes tests.

Props SergeyBiryukov.
Fixes #1850.