Good catch. Can you first submit a PR on 2.8 to generate deprecation notices when a call to these methods uses $deep as true? Thanks.

@fabpot I'll do it this Wednesday

I don't think we need deprecation message for those methods because it calls get internally which already creates a deprecation message.

But we need to trigger a deprecation message for filter and change the signature in 2.8 with BC layer. Even when calling filter with deep=false it must create a warning because it's in the middle of the parameters.

@Tobion
Do you mean change the signature to

public function filter($key, $default = null, $filter = FILTER_DEFAULT, $options = array(), $deep = false)

but check if $filter is a boolean ($deep) or an integer (right $filter)?

Yes. Basically change the signature to the new one: public function filter($key, $default = null, $filter = FILTER_DEFAULT, $options = array()) And then check if $filter is a boolean. And if yes trigger deprecation, treat params like the old signature and use func_get_arg to get the last one.

Sorry for the late response
See #16703

Will need to be rebased once #16706 is merged

Thank you @belka-ew.