Hardcoded check for image block if a custom plugin specifies any blocktype, preventing installation + fix

[Matt Gibson]

I'm coding a new artefact plugin and I've found that if I specify anything at all in the get_block_types() function of the main artefact class, installation fails because I haven't got class PluginBlocktypeImage available.

This comes from a loop in artefact_check_plugin_sanity() (/artefact/lib.php around line 1150), which reads

foreach ($types as $type) {
        $pluginclassname = generate_class_name('blocktype', 'image');

        // other stuff that's not relevant up to line 1168

        if (!class_exists($pluginclassname)) {
            throw new InstallationException(get_string('classmissing', 'error', $pluginclassname, $type, $pluginname));
        }
}

The plugin class name needs to generated dynamically:

$pluginclassname = generate_class_name('blocktype', $type);