Extend/split IgnoreUndeclared to ignore undeclared attributes on assignment and fetch

[jhaesus]

require 'hashie'
class Something < Hashie::Trash
    include Hashie::Extensions::DeepMerge
    include Hashie::Extensions::IgnoreUndeclared
    property :some_key
end

item = Something.new(some_ignored_key: 17, some_key: 12)
item.deep_merge(some_other_key: 55)

raises "NoMethodError: The property 'some_other_key' is not defined for this Trash."

[dblock]

I tried this out, see dblock@6b1192b.

With IgnoreUndeclared the behavior of assigning an undeclared property explicitly is still to raise a NoMethodError. That extension is only ignoring properties on initialization by design.

We probably want an extension that also behaves in a similar way on assignment. Maybe split IgnoreUndeclared into IgnoreUndeclaredInitialize, IgnoreUndeclaredAssign and IgnoreUndeclaredFetch? I'll leave this open as a feature request and rename.