[issue41842] Add codecs.unregister() to unregister a codec search function

[Marc-Andre Lemburg]

Marc-Andre Lemburg <mal at egenix.com> added the comment:

On 23.09.2020 16:49, STINNER Victor wrote:
> 
> STINNER Victor <vstinner at python.org> added the comment:
> 
>> Just found an internal API which already takes care of
>> unregistering a search function: _PyCodec_Forget().
>>
>> All that needs to be done is to expose this as codecs.unregister()
>> and add the clearing of the lookup cache.
> 
> Yeah, I saw this function, but it's related to the cache, not to the list of search functions.

Ah, right. I just looked at the first occurance of codec_search_path :-)

>> BTW: While you're at it, having a way to access the search function
>> list from Python would be nice as well, since this would then open
>> up the possibility to reorder search functions.
> 
> I didn't hear anyone (ok, apart you) who requested to order search functions.

This has come up in the past from people who wanted to override
builtin codecs with their own versions.

> I dislike the idea of exposing it, since it introduces the risk that someone "unregisters" a search function simply by removing it from the list, without invalidating the cache.
> 
> I prefer to hide the internals to ensure that the cache remains consistent.

Sure, a function would merely return a tuple with the entries,
not the list itself, e.g. in pseudo code:

def get_search_path():
    return tuple(interp->codec_search_path)

For replacing the vanilla setup, this is not needed, since only
one search function gets registered (the builtin one), so rather
low priority, I guess.

-- 
Marc-Andre Lemburg
eGenix.com

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