Error when upgrading to Moodle 5.2

[jkram]

Moodle version info

$version  = 2026042000.02;              // 20260420      = branching date YYYYMMDD - do not modify!
                                        //         RR    = release increments - 00 in DEV branches.
                                        //           .XX = incremental changes.
$release  = '5.2+ (Build: 20260501)';    // Human-friendly version name

When attempting to upgrade from 4.5 to 5.2, it errored out with:

-->System
++ 2025051600.02: Success (0.33 seconds) ++
++ 2025053000.02: Success (0.03 seconds) ++
++ 2025062900.01: Success (0.03 seconds) ++
++ 2025070600.01: Success (0.03 seconds) ++
++ 2025072500.01: Success (0.03 seconds) ++
++ 2025073100.01: Success (0.03 seconds) ++
-->block_section_links
Default exception handler: Exception - Call to undefined function Aws\manifest() Debug: 
Error code: generalexceptionmessage
* line 242 of /public/lib/aws-sdk/src/AwsClient.php: Error thrown
* line 439 of /public/lib/aws-sdk/src/S3/S3Client.php: call to Aws\AwsClient->__construct()
* line 804 of /public/lib/aws-sdk/src/AwsClient.php: call to Aws\S3\S3Client->__construct()
* line 187 of /public/admin/tool/objectfs/classes/local/store/s3/client.php: call to Aws\AwsClient::factory()
* line 90 of /public/admin/tool/objectfs/classes/local/store/s3/client.php: call to tool_objectfs\local\store\s3\client->set_client()
* line 50 of /public/admin/tool/objectfs/classes/local/store/s3/file_system.php: call to tool_objectfs\local\store\s3\client->__construct()
* line 84 of /public/admin/tool/objectfs/classes/local/store/object_file_system.php: call to tool_objectfs\local\store\s3\file_system->initialise_external_client()
* line 81 of /public/lib/filestorage/file_storage.php: call to tool_objectfs\local\store\object_file_system->__construct()
* line 62 of /public/lib/filestorage/file_storage.php: call to file_storage->setup_file_system()
* line 6381 of /public/lib/moodlelib.php: call to file_storage->__construct()
* line 250 of /public/lib/adminlib.php: call to get_file_storage()
* line 1252 of /public/lib/db/upgrade.php: call to uninstall_plugin()
* line 1889 of /public/lib/upgradelib.php: call to xmldb_main_upgrade()
* line 268 of /admin/cli/upgrade.php: call to upgrade_core()

Upon disabling the alternative_file_system_class in config.php

//$CFG->alternative_file_system_class = '\tool_objectfs\s3_file_system';

the upgrade went further... but then errored with the same:

++ external_update_services: Success (3.71 seconds) ++
++ Success (4.01 seconds) ++
== Setting new default values ==
Default exception handler: Exception - Call to undefined function Aws\manifest() Debug: 
Error code: generalexceptionmessage
* line 242 of /public/lib/aws-sdk/src/AwsClient.php: Error thrown
* line 439 of /public/lib/aws-sdk/src/S3/S3Client.php: call to Aws\AwsClient->__construct()
* line 804 of /public/lib/aws-sdk/src/AwsClient.php: call to Aws\S3\S3Client->__construct()
* line 187 of /public/admin/tool/objectfs/classes/local/store/s3/client.php: call to Aws\AwsClient::factory()
* line 90 of /public/admin/tool/objectfs/classes/local/store/s3/client.php: call to tool_objectfs\local\store\s3\client->set_client()
* line 132 of /public/admin/tool/objectfs/classes/local/manager.php: call to tool_objectfs\local\store\s3\client->__construct()
* line 145 of /public/admin/tool/objectfs/settings.php: call to tool_objectfs\local\manager::get_client()
* line 81 of /public/lib/classes/plugininfo/tool.php: call to include()
* line 763 of /public/admin/settings/plugins.php: call to core\plugininfo\tool->load_settings()
* line 8930 of /public/lib/adminlib.php: call to require()
* line 8959 of /public/lib/adminlib.php: call to admin_get_root()
* line 281 of /admin/cli/upgrade.php: call to admin_apply_default_settings()

In order to complete the upgrade, I removed the admin/tool/objectfs entirely

[jkram]

After the upgrade, adding the tool/objectfs code back, and enabling the alt filesystem class again, the Moodle 5.2 upgraded site front-end exhibits the same error:

[justinhunt]

I had this issue also. The solution was to run the following from the root of the Moodle program directory. (If you have not installed Composer you will need to do that first)
sudo -u www-data composer install --no-dev --classmap-authoritative
This generates: vendor/autoload.php , and that is how enormous AWS sdk is mapped and its functions/classes can be found