ruby-core

Issue #15863 has been updated by shevegen (Robert A. Heiler).


I do not know how Hash#extract from Active* works but the name does not make to me
a whole lot of sense to me; however had, we have Hash#slice already so I guess it may
make sense to add .slice!; and if so, it may make sense to add it for ENV as
ENV is very hash-like. But I may miss something altogether - this may be best
to actually suggest to the upcoming developer meeting, since it is a fairly small
request/possible change, anyway. (I don't feel I should add it myself because
you suggested it so you should be in control over as to whether you want to 
suggest it or not - that is not my decision what you make of course. :))

The next meeting is at:

https://bugs.ruby-lang.org/issues/15782

As for behaviour - this is not necessarily specific to your proposal alone,
but I think ruby users will expect that the trailing "!" indicates a warning
or rather an operation that may be "dangerous" or have side effects - the most
usual one being modifying the receiver in place (or something like that). Not
all methods have a trailing !, for example, replace() on class String. I think
the bottom line is that matz wanted a simple visual cue/indicator for ruby.

So I think whatever the feature request or desired change, I think the most
natural assumption would be that a variant with ! will do precisely the same
as the non-! variant, as action, but without modifying the object at hand.
It is for this reason that I believe that .slice! could (or should) not model
any other behaviour than what .slice() is doing right now. But as said, I may
be missing something; perhaps there was a reason .slice!() was not added,
I would not know.

----------------------------------------
Feature #15863: Add `Hash#slice!` and `ENV.slice!`
https://bugs.ruby-lang.org/issues/15863#change-78082

* Author: bogdanvlviv (Bogdan Denkovych)
* Status: Open
* Priority: Normal
* Assignee: 
* Target version: 
----------------------------------------
## Add `Hash#slice!`

In https://bugs.ruby-lang.org/issues/8499 we added `Hash#slice`.

`Hash#slice!` removes and returns the key/value pairs matching the given keys:

```ruby
h = {a: 100, b: 200, c: 300}
h.slice!(:a) # => {:a=>100}
h # => {:b=>200, :c=>300}
h.slice!(:b, :c, :d) # => {:b=>200, :c=>300}
h # => {}
```

Note that, this method reflects the behavior of Active Support's
`Hash#extract!` method that was added in 2009, see
https://github.com/rails/rails/commit/8dcf91ca113579646e95b0fd7a864dfb6512a53b

```ruby
h = {a: 100, b: 200, c: 300}
h.extract!(:a) # => {:a=>100}
h # => {:b=>200, :c=>300}
h.extract!(:b, :c, :d) # => {:b=>200, :c=>300}
h # => {}
```
(There is a proposal to add `Hash#extract` to Ruby - https://bugs.ruby-lang.org/issues/15831, but it has another method signature)

Active Support also has `Hash#slice!`, see https://api.rubyonrails.org/v5.2/classes/Hash.html#method-i-slice-21.
It is quite different what this patch proposes, see how it works:

```ruby
h = {a: 100, b: 200, c: 300}
h.slice!(:a) # => {:b=>200, :c=>300} # AS Hash#slice!
h # => {:a=>100}
h.slice!(:b, :c, :d) # => {:a=>100} # AS Hash#slice!
h # => {}
```

I think `Hash#slice!` in Ruby should work in the same way as `Hash#extract!` from Active Support,
there is one argument:
- https://bugs.ruby-lang.org/issues/8499#note-31
  It should behave in the way `Hash#slice` does, except one thing
  `Hash#slice!` modifies the object. (See, for instance, how `Array#slice` and
  `Array#slice!` work, they return the same value)

But I would like to discuss it more to choose the right behavior for the
proposed method. (Maybe there are good arguments why we should add `Hash#slice!`
with behavior as it is in Active Support)


## Add `ENV.slice!`

The method removes and returns the key/value pairs matching the given keys.

```ruby
ENV.slice!("PORT", "RAILS_ENV") # => {"PORT"=>"3000", "RAILS_ENV"=>"development"}
```


Pull Request: https://github.com/ruby/ruby/pull/2195
Patch: https://patch-diff.githubusercontent.com/raw/ruby/ruby/pull/2195.patch



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