[ruby-core:76413] [Ruby trunk Feature#12350] Introduce Array#find! that raises an error if element not found

Issue #12350 has been updated by Yukihiro Matsumoto.


I am not against adding a method that raises an exception, but `find!` is not a proper name for it.
Besides that, we can raise an exception for non-existing values by the current behavior.
So let us start improving documentation. Daniel, could you create an PR?

Matz.


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Feature #12350: Introduce Array#find! that raises an error if element not found
https://bugs.ruby-lang.org/issues/12350#change-59653

* Author: Andrey Koleshko
* Status: Open
* Priority: Normal
* Assignee: 
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It would be great to have some function (like `Hash#fetch`) for `Array` that raises an exception if element not found by passed block in `find`.

For example:

~~~
[].find! { |el| el == 1 }
=> ElementError: element not found
~~~

I just noticed that there are many cases when it's needed to raise an exception (because this is exceptional situation) if an element not found.


Currently I just define methods like  this one:

~~~
def find_price!(size)
  found_price = prices.find { |p| p.key == size }
  fail "Price for #{size} not found" unless found_price
  found_price
end
~~~




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