Difference between tap / delete and except in Ruby Hash

[titan2gman]

I am facing a very curious behavior. This is Ruby 2.6.6, so a frozen hash can be modified. In this example, source is frozen.

Doing this:

result = source.tap { |s| s.delete(:key) }
Brings back a copy of the source without the :key key.

In theory, so does this:

result = source.except(:key)
and this as well:

result = source.dup.tap { |s| s.delete(:key) }
To my understanding, the above 3 syntaxes have identical outcome.

However, in tests (Ruby 2.6.6, Rails 6.0.6.1) the spec with the first syntax succeeds and the latter two fail. I don't know if it is important to state which test exactly, I am just looking for an explanation.

Any suggestion as to why would this be happening?

Thanks in advance.

[fortune-web]

Object#tap. Object#tap:

Yields self to the block, and then returns self. The primary purpose of this method is to “tap into” a method chain, in order to perform operations on intermediate results within the chain.

This does not create a "copy" so by using Hash#delete you are modifying source in place.