Allow AR::Enum definitions with boolean values

[yhirano55]

Summary

If AR::Enum is used for boolean field, it would be not expected behavior for us.

fixes #38075

Problem

In case of using boolean for enum, we can set with string (hash key)
to instance, but we cannot set with actual value (hash value).

class Post < ActiveRecord::Base
  enum status: { enabled: true, disabled: false }
end

post.status = 'enabled'
post.status # 'enabled'

post.status = true
post.status # 'enabled'

post.status = 'disabled'
post.status # 'disabled'

post.status = false
post.status # nil (This is not expected behavior)

After looking into AR::Enum::EnumType#cast, I found that blank? method converts from false value to nil (it seems it may not intentional behavior).

rails/activerecord/lib/active_record/enum.rb

Lines 125 to 135 in 1421ad5

	def cast(value)
	return if value.blank?
	if mapping.has_key?(value)
	value.to_s
	elsif mapping.has_value?(value)
	mapping.key(value)
	else
	assert_valid_value(value)
	end
	end

In this patch, I improved that if it defines enum with boolean, it returns reasonable behavior.

Importance (Why it would be better to merge this patch)

• I am working on a legacy project that has enums with booleans as their values.
• The project's team had never noticed this behavior before because they had been assigning values using the enum key strings, i.e. post.status = 'disabled'.
• I stumbled upon this behavior when I wrote a test that called post.disabled!.
• The assertion at assert_valid_enum_definition_values permits boolean-valued hashes, which tells me that this is a feature that we may want to support, so I made these changes to reflect that.

^ This messages are translated by my co-worker @rastamhadi

[ugisozols]

I understand the legacy project issue but using enum in a place where a boolean attribute should have been used in the first place feels very unnatural. It's also asking for some head-scratching down the road if someone adds more statuses like enum status: { enabled: true, disabled: false, pending: 1 }. Just my 2c ❤️ 😉

[kamipo]

Can you add test mapping nil (@book.read_status = nil) too?
This implementation will also change the mapping nil behavior regardless of whether what you want.

[yhirano55]

@kamipo Thank you for the comment. I added a test case against mapping nil.