[ruby-core:119484] [Ruby master Feature#20738] Removing a specific entry from a hash literal

Issue #20738 has been updated by ursm (Keita Urashima).


OK, I'm sorry to hear that, but I'm glad to hear your opinions. Thanks.

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Feature #20738: Removing a specific entry from a hash literal
https://bugs.ruby-lang.org/issues/20738#change-110101

* Author: ursm (Keita Urashima)
* Status: Open
----------------------------------------
Sometimes I want to decide whether or not to add a particular entry to a hash depending on a condition. If the entire hash does not use nil, I can use Hash#compact.

```ruby
{
  foo: 1,
  bar: bar? ? 2 : nil
}.compact
```

But if I want to remove only a specific entry while leaving the other nil, it is somewhat cumbersome. I have to either assign the hash once and change it destructively, or use Hash#reject.

``` ruby
h = {
  foo: 1,
  baz: nil
}

h[:bar] = 2 if bar?
```
``` ruby
{
  foo: 1,
  bar: bar? ? 2 : :drop,
  baz: nil
}.reject {|_, v| v == :drop }
```

As a suggestion, how about a special value that indicates an invalid key for the hash? With this, the above example could be written like this:

``` ruby
{
  foo: 1,
  bar: bar? ? 2 : Hash::DROP,
  baz: nil
} #=> {foo: 1, baz: nil}
```



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