Topic on Project:Support desk

Hi,

I'm re-installing Mediawiki 1.37 on a fresh Ubuntu 22.04, Apache, PHP 8.1. I get the first config screen (lang), I click for the following step, and... fail!

/w/mw-config/index.php?page=Language Error: Class "FormatJson" not found

Backtrace:
from /var/www/wiki/w/includes/exception/MWExceptionHandler.php(754)
 #0 /var/www/wiki/w/includes/exception/MWExceptionHandler.php(291): MWExceptionHandler::logError()
 #1 /var/www/wiki/w/includes/AutoLoader.php(117): MWExceptionHandler::handleError()
 #2 /var/www/wiki/w/includes/AutoLoader.php(117): require(string)
 #3 /var/www/wiki/w/includes/cache/localisation/LocalisationCache.php(594): AutoLoader::autoload()
 #4 /var/www/wiki/w/includes/cache/localisation/LocalisationCache.php(929): LocalisationCache->readJSONFile()
 #5 /var/www/wiki/w/includes/cache/localisation/LocalisationCache.php(496): LocalisationCache->recache()
 #6 /var/www/wiki/w/includes/cache/localisation/LocalisationCache.php(370): LocalisationCache->initLanguage()
 #7 /var/www/wiki/w/includes/cache/localisation/LocalisationCache.php(311): LocalisationCache->loadItem()
 #8 /var/www/wiki/w/includes/language/LanguageFallback.php(106): LocalisationCache->getItem()
 #9 /var/www/wiki/w/includes/language/LanguageFactory.php(158): MediaWiki\Languages\LanguageFallback->getAll()
 #10 /var/www/wiki/w/includes/language/LanguageFactory.php(116): MediaWiki\Languages\LanguageFactory->newFromCode()
 #11 /var/www/wiki/w/mw-config/index.php(75): MediaWiki\Languages\LanguageFactory->getLanguage()
 #12 /var/www/wiki/w/mw-config/index.php(40): wfInstallerMain()
 #13 {main}

What is wrong ?

You are missing MediaWiki files or your install is corrupt. I would suggest re-installing.

I tried the installation several times from the 1.37.2 .zip or tar.gz archive. I moves the files in place together with a <code>cp -r /path/to/source/* /path/to/target</code> and changed the owner with a <code>chown -R www-data:www-data /path/to/target</code> I doubt I forgot a file each time, and always the same to get the same error. Maybe a php file. But witch ? My phpinfo says that JSON is enabled.

The missing file would be includes/json/FormatJson.php

<code>ls /var/www/wiki/w/includes/json/</code>

returns :

<code>

FormatJson.php     JsonSerializer.php           JsonUnserializer.php

JsonCodec.php      JsonUnserializable.php

JsonConstants.php  JsonUnserializableTrait.php

</code>

The FormatJson.php file is here.

Check it has the same contents as https://github.com/wikimedia/mediawiki/blob/REL1_37/includes/json/FormatJson.php (especially line 1 and 26, but whole thing should be the same) and also check line 539 of autoload.php is the same as https://github.com/wikimedia/mediawiki/blob/REL1_37/autoload.php#L539

Php 8.1 isn't officially supported by mediawiki 1.37, but it feels really unlikely that any incompatibility would manifest like this. However it seems like some other people have the same error https://phabricator.wikimedia.org/T307816 which is very weird (edit: i didnt realize you were same person)

If you want to further debug you could add something like the following to line 115 of includes/AutoLoader.php https://github.com/wikimedia/mediawiki/blob/REL1_37/includes/AutoLoader.php#L115

(This will break things so remove after)

if ($className=="FormatJson") {var_dump($className, $filename);die()}

That should cause mediawiki to show what path its looking for FormatJson

Compared with meld :

• https://github.com/wikimedia/mediawiki/blob/REL1_37/includes/json/FormatJson.php
• /var/www/wiki/w/includes/json/FormatJson.php

No difference (just an empy ending line on the git version).

Compared with meld :

• https://github.com/wikimedia/mediawiki/blob/REL1_37/autoload.php
• /var/www/wiki/w/autoload.php

No difference.

I have added the empty line at the end of FormatJson.php. And the installation seems running.

Let us have a look further.

OK. WIki installed.

Thanks.

Thats still super weird as an empty line at end should affect nothing. Maybe some sort of opcode cache issue and editing the file forced a cache clear.

FYI - happened to me also, adding a newline at the end of FormatJson solves the issue.

thanks, that did the trick for me. just add new line

For keeping track, links and history in search engines :

The issue was open also on Phabricator : https://phabricator.wikimedia.org/T307816