Add a PermissiveRespondTo extension for Mashes

By default, Mashes don't state that they respond to unset keys. This
causes unexpected behavior when you try to use a Mash with a
SimpleDelegator.

This new extension allows you create a permissive subclass of Mash that
will be fully compatible with SimpleDelegator and allow you to fully do
thunk-oriented programming with Mashes.

This comes with the trade-off of a ~19KB cache for each of these
subclasses and a ~20% performance penalty on any of those subclasses.

1 files changed, 44 insertions, 0 deletions

diff --git a/spec/hashie/extensions/mash/permissive_respond_to_spec.rb b/spec/hashie/extensions/mash/permissive_respond_to_spec.rb
new file mode 100644
index 0000000..189f94a
--- /dev/null
+++ b/spec/hashie/extensions/mash/permissive_respond_to_spec.rb
@@ -0,0 +1,44 @@
+require 'spec_helper'
+
+RSpec.describe Hashie::Extensions::Mash::PermissiveRespondTo do
+  class PermissiveMash < Hashie::Mash
+    include Hashie::Extensions::Mash::PermissiveRespondTo
+  end
+
+  it 'allows you to bind to unset getters' do
+    mash = PermissiveMash.new(a: 1)
+    other_mash = PermissiveMash.new(b: 2)
+
+    expect { mash.method(:b) }.not_to raise_error
+    expect(mash.method(:b).unbind.bind(other_mash).call).to eq 2
+  end
+
+  it 'works properly with SimpleDelegator' do
+    delegator = Class.new(SimpleDelegator) do
+      def initialize(hash)
+        super(PermissiveMash.new(hash))
+      end
+    end
+
+    foo = delegator.new(a: 1)
+
+    expect(foo.a).to eq 1
+    expect { foo.b }.not_to raise_error
+  end
+
+  context 'warnings' do
+    include_context 'with a logger'
+
+    it 'does not log a collision when setting normal keys' do
+      PermissiveMash.new(a: 1)
+
+      expect(logger_output).to be_empty
+    end
+
+    it 'logs a collision with a built-in method' do
+      PermissiveMash.new(zip: 1)
+
+      expect(logger_output).to match('PermissiveMash#zip defined in Enumerable')
+    end
+  end
+end