user-library class loading

[eluser]sipsniffa[/eluser]
Hi,

I recently ran into a problem when trying to load my own CodeIgniter library. I initially posted a query to the 'Code and Application' forum and finally posted on what may be a bug. The problem was related to the use of the 'subclass_prefix' configuration option and its possible misuse in the CI code base or missing documentation.

The problem is caused by trying to load a user-library (placed in application/libraries/) without assigning a value to the 'subclass_prefix' configuration option (i.e. 'subclass_prefix' took the default, empty string value). This results in user library classes being deemed attempts to subclass CodeIgniter library classes (code snipped from _ci_load_class() in system/library/Loader.php):

Code:

$subclass = APPPATH.'libraries/'.$subdir.config_item('subclass_prefix').$class.EXT;

// Is this a class extension request?            
if (file_exists($subclass))
{
    // ...
}

The decision of whether the user's library class ($class) is a subclass is in error. A user's library class is deemed to be a subclass by concatenating its name with the config value ‘subclass_prefix’ and the '.php' extension and then checking whether that file exists on the file system. When 'subclass_prefix' is empty, a user library class will always be deemed a CI subclass! Now when a CI base-class by the same name cannot be found the _ci_load_class() function bombs out with a show_error() call:

Code:

$subclass = APPPATH.'libraries/'.$subdir.config_item('subclass_prefix').$class.EXT;
    
// Is this a class extension request?            
if (file_exists($subclass))
{
    $baseclass = BASEPATH.'libraries/'.ucfirst($class).EXT;

    if ( ! file_exists($baseclass))
    {
        log_message('error', "Unable to load the requested class: ".$class);
        show_error("Unable to load the requested class: ".$class);
    }

    // ...

}

I think that the initial subclass test doesn't make sense when ‘subclass_prefix’ is the empty string. Might this be considered a bug, either in the documentation or in code?:

1. Documentation Bug
I haven't seen it mentioned in the docs, but if a client wishes to implement a CI user-library then it would be helpful if the docs stated that a value must be assigned to the 'subclass_prefix' configuration option - even when no subclassing of CI libraries is to undertaken.

2. Code Bug
One possibility that comes to mind as a code fix would be to prohibit library subclassing if the configuration setting 'subclass_prefix' contains it's default, empty string value ('').
I think this could be achieved by placing a guard around the subclass test code - which I highlighted above - like so:

Code:

// Subclassing only allowed when 'subclass_prefix' is defined.
if (strlen(config_item('subclass_prefix')) !== 0)
{
    $subclass = APPPATH.'libraries/'.$subdir.config_item('subclass_prefix').$class.EXT;

    // Is this a class extension request?            
    if (file_exists($subclass))
    {
        // ...
    }
}

I think this is a more elegant solution and demands less of the user than the documentation option.

While looking at _ci_load_class() there appears to be code that is ripe for refactoring.

I'd be grateful if someone could explain the process used by EllisLab when handling community offerings of code.

Thanks,

Paul.