Allow ActionController::Parameters as inputs

This fixes #381.

lib/active_interaction/base.rb

@@ -169,8 +169,7 @@ def eagerly_evaluate_default(filter)
     #
     # @private
     def initialize(inputs = {})
-      raise ArgumentError, 'inputs must be a hash' unless inputs.is_a?(Hash)
-
+      inputs = normalize_inputs!(inputs)
       process_inputs(inputs.symbolize_keys)
     end
 
@@ -234,6 +233,22 @@ def run_validations!
 
     private
 
+    # We want to allow both `Hash` objects and `ActionController::Parameters`
+    # objects. In Rails < 5, parameters are a subclass of hash and calling
+    # `#symbolize_keys` returns the entire hash, not just permitted values. In
+    # Rails >= 5, parameters are not a subclass of hash but calling
+    # `#to_unsafe_h` returns the entire hash.
+    def normalize_inputs!(inputs)
+      return inputs if inputs.is_a?(Hash)
+
+      klass = 'ActionController::Parameters'.safe_constantize
+      if !klass || !inputs.is_a?(klass)
+        raise ArgumentError, 'inputs must be a hash'
+      end
+
+      inputs.to_unsafe_h
+    end
+
     # @param inputs [Hash{Symbol => Object}]
     def process_inputs(inputs)
       @_interaction_keys = inputs.keys.to_set & self.class.filters.keys

spec/active_interaction/base_spec.rb

@@ -1,6 +1,7 @@
 # coding: utf-8
 
 require 'spec_helper'
+require 'action_controller'
 
 InteractionWithFilter = Class.new(TestInteraction) do
   float :thing
@@ -58,6 +59,22 @@ def execute
       end
     end
 
+    context 'with non-hash inputs' do
+      let(:inputs) { [[:k, :v]] }
+
+      it 'raises an error' do
+        expect { interaction }.to raise_error ArgumentError
+      end
+    end
+
+    context 'with ActionController::Parameters inputs' do
+      let(:inputs) { ActionController::Parameters.new }
+
+      it 'does not raise an error' do
+        expect { interaction }.to_not raise_error
+      end
+    end
+
     context 'with a reader' do
       let(:described_class) do
         Class.new(TestInteraction) do