Problem/Motivation
When a library version is defined as a string, we get the notice: Notice: Uninitialized string offset: 0 in Drupal\Core\Asset\LibraryDiscoveryParser->buildByExtension() (line 145 of /core/lib/Drupal/Core/Asset/LibraryDiscoveryParser.php
Steps to reproduce
Enable the dblog module
Install any contrib module (such as devel) or in any custom module that have a library.yml file defining a version with a integer/string such as version: 0.
Check your dblog report, and you should have a record similar to:
Notice: Uninitialized string offset: 0 in Drupal\Core\Asset\LibraryDiscoveryParser->buildByExtension() (line 145 of /web/core/lib/Drupal/Core/Asset/LibraryDiscoveryParser.php)
Proposed resolution
The current code on LibraryDiscoveryParser.php checks for $library['version'][0] without prior checking if the array index exists.
I'm proposing to update that elseif statement to first check if the array index exists.
Original code:
elseif (is_string($library['version']) && $library['version'][0] === 'v') {
Proposed code:
elseif (is_string($library['version']) && isset($library['version'][0]) && $library['version'][0] === 'v') {