[ruby-core:108691] [Ruby master Feature#14602] Version of dig that raises error if a key is not present

Issue #14602 has been updated by zverok (Victor Shepelev).


I fully agree with @duerst in #14602#note-24: 

> maybe we can think it as a combination of `dig` with `fetch`. Then what about `dig_fetch` or `fetch_dig`? These names don't look very natural, but it's easy to understand what they are about.

First, we **already have examples of `fetch`-based naming**: not only `#fetch` itself as a variation of `#[]`, but also `#fetch_values` as a variation of `#values_at`, so there is a precedent for **recognizability**

Second, I value short one-word names, so all the witty options like `#shovel` and `#retrieve` are nice, but I am afraid that when we have a variation of a known method in an API established long ago, introducing **completely new word** into Ruby would be a false move. Imagine you started to read code and met with `#retrieve` (or `#shovel`) for the first time. There is nothing that might help you to understand what it does; one verb that "a bit resembles `dig`" is not suggestive enough.

Third, `deep_fetch` **is** somewhat suggestive, but the problem "it behaves like `dig`, but the name logic is nothing like `dig`" stands. Maybe if it would a pair of, IDK, `#deep_fetch` and `#deep_get` it might've been tolerable, but now is too late for that, everybody has used to `#dig`.

`fetch_dig`, OTOH, is reasonably short, clearly suggests the meaning, and follows the logic of other methods existing.

----------------------------------------
Feature #14602: Version of dig that raises error if a key is not present
https://bugs.ruby-lang.org/issues/14602#change-97736

* Author: amcaplan (Ariel Caplan)
* Status: Open
* Priority: Normal
----------------------------------------
Currently, if I have a hash like this:

~~~ ruby
{
    :name => {
        :first => "Ariel",
        :last => "Caplan"
    }
}
~~~

and I want to navigate confidently and raise a KeyError if something is missing, I can do:

~~~ ruby
hash.fetch(:name).fetch(:first)
~~~

Unfortunately, the length of the name, combined with the need to repeat the method name every time, means most programmers are more likely to do this:

~~~ ruby
hash[:name][:first]
~~~

which leads to many unexpected errors.

The Hash#dig method made it easy to access methods safely from a nested hash; I'd like to have something similar for access without error protection, and I'd think the most natural name would be Hash#dig!.  It would work like this:

~~~ ruby
hash = {
    :name => {
        :first => "Ariel",
        :last => "Caplan"
    }
}
hash.dig!(:name, :first) # => Ariel
hash.dig!(:name, :middle) # raises KeyError (key not found: :middle)
hash.dig!(:name, :first, :foo) # raises TypeError (String does not have #dig! method)
~~~




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