Support clearing acronyms from inflector

[odlp]

Summary

Attempting to clear acronyms in the Inflector breaks the implementation. This results in a TypeError when attempting to set another acronym:

require "bundler/inline"

gemfile do
  source "https://rubygems.org"
  gem "activesupport", require: "active_support/all"
end

ActiveSupport::Inflector.inflections do |inflect|
  inflect.clear :acronyms
  inflect.acronym "HTML" # => '[]=': no implicit conversion of String into Integer (TypeError)
end

This is because #clear sets a new Array for @acronyms:

rails/activesupport/lib/active_support/inflector/inflections.rb

Lines 233 to 234 in 051b0fc

	else
	instance_variable_set "@#{scope}", []

Rather than a Hash (the default initialized value):

rails/activesupport/lib/active_support/inflector/inflections.rb

Lines 78 to 79 in 051b0fc

	def initialize
	@plurals, @singulars, @uncountables, @humans, @acronyms = [], [], Uncountables.new, [], {}

This PR also extends ActiveSupport::Inflector::Inflections#clear / #clear(:all) to clear acronyms, since this wasn't covered.

Other Information

I discovered this issue whilst writing a test for rails/activeresource#361

[ghiculescu]

I think this does the same thing as #40790

[odlp]

@ghiculescu apologies I didn't spot your PR, you noticed this a while back!

Happy to close this PR / combine efforts / what ever you prefer – it'd be good to get this fixed 😄

[ghiculescu]

I don't mind which PR gets merged, as long as the issue is fixed :) It looks like we have ended up on the same implementation 😆 Do you want to just check that the tests I added in mine, also work in yours? If you like, you can add them to this PR and I can close mine.

[odlp]

Thanks @ghiculescu, I moved across two tests from your PR.

In particular the extra test which exercises #define_acronym_regex_patterns is called is a great shout 🎉

[ghiculescu]

Looks good to me. Can you please squash?

[rails-bot]

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