This is still confusing to me but I guess it's because we can have only one filter when Config\Feature::multipleFilters is disabled.

Will this gonna end up as:

$expected = [
    'admin/dashboard' => [
        'filter' => ['csrf'],
    ],
    'admin/profile' => [
        'filter' => ['csrf', 'honeypot'],
    ],
];

when multipleFilters option will be enabled?

No. it is just because using array_merge().
https://3v4l.org/tskmm

It is the current behavior that filters are not merged, and also the reason why the Note in the user guide was added.

One possible behavior would be to merge filters as well, but then it would not be possible to delete filters in inner group. Multiple filters are already the default in 4.5.

Good point about removing filters.

I don't know... now I'm leaning towards staying with the current behavior and not inheriting anything. Because the new behavior seems even more confusing - it's inherited only if there are no other filters. I can imagine people adding a new filter over time and "losing" functionality.

Thanks to the current note, at least we have clear rules to follow.

The current behavior is not that straightforward either.
The current behavior is that if you don't pass an options array to the inner group, the outer options are inherited.

That's why when you set outer filter and add namespace option to inner group, the filter that set in outer suddenly will be gone for the inner route.

It seems that this issue is not so easy to conclude.

Yes, this is a bit more complex than I thought at first. Especially if we add namespaces to it.

Personally, I would probably merge all the declared filters from the external to the internal group using array_merge_recursive and introduce something like filterExclude to remove the filters if needed. However, this seems a bit too complex... not sure if we want to make such big changes.

Although the rules would be clear and need no further explanation.

I am very sorry for my translation.

Yes, to exclude the outside filter, I gave an example of except in the Config. Or we need to write such a filter for all routes except unnecessary ones (this is your option)

I disagree with the new feature to exclude route filters in the Config\Filter.
The Config\Filter and route filters are the same filters, but I think mixing these settings is a source of confusion.

Also, I don't like to add a new key for excluding filters in the route option.
It also is complicated.

Well, this does not cancel your method - we leave the outside filters empty and configure each route individually

I'm sorry, but what you don't like about the exception in the Config is a function of the framework. There is no other way to fine tune

Config\Filter defines filters for URI paths, not for routes.
except excepts the filter to the URI path in Config\Filter.
https://codeigniter4.github.io/CodeIgniter4/incoming/filters.html#except-for-a-few-uris

Filters for a route are different things. If you specify a filter to a route, it is always applied.
The definitions in Config\Filter does nothing to route filters.

What I don't like is to mix the two kind of filters. That is, except in Config\Filter excepts route filters, too.
It is really complicated and confusing.

@michalsn @neznaika0 @MGatner I changed my mind. I sent another PR #8033 that behaves like michalsn expects in #7981 (comment)