Add permitted_attributes_for_#{action} hook

Allows separate attributes for different actions. Closes #340

lib/pundit.rb

@@ -139,15 +139,15 @@ module Pundit
     policies[record] ||= Pundit.policy!(pundit_user, record)
   end
 
-  def permitted_attributes(record)
-    name = if record.respond_to?(:model_name)
-      record.model_name.param_key
-    elsif record.is_a?(Class)
-      record.to_s.demodulize.underscore
+  def permitted_attributes(record, action=params[:action])
+    param_key = PolicyFinder.new(record).param_key
+    policy = policy(record)
+    method_name = if policy.respond_to?("permitted_attributes_for_#{action}")
+      "permitted_attributes_for_#{action}"
     else
-      record.class.to_s.demodulize.underscore
+      "permitted_attributes"
     end
-    params.require(name).permit(policy(record).permitted_attributes)
+    params.require(param_key).permit(policy.public_send(method_name))
   end
 
   def policies

lib/pundit/policy_finder.rb

@@ -59,6 +59,18 @@ module Pundit
       policy or raise NotDefinedError, "unable to find policy `#{find}` for `#{object.inspect}`"
     end
 
+    # @return [String] the name of the key this object would have in a params hash
+    #
+    def param_key
+      if object.respond_to?(:model_name)
+        object.model_name.param_key.to_s
+      elsif object.is_a?(Class)
+        object.to_s.demodulize.underscore
+      else
+        object.class.to_s.demodulize.underscore
+      end
+    end
+
   private
 
     # @return [String] policy class name

spec/pundit_spec.rb

@@ -430,6 +430,20 @@ describe Pundit do
     end
   end
 
+  describe "#permitted_attributes_for_action" do
+    it "is checked if it is defined in the policy" do
+      params = ActionController::Parameters.new({ action: 'revise', post: { title: 'Hello', body: "blah", votes: 5, admin: true } })
+
+      expect(Controller.new(user, params).permitted_attributes(post)).to eq({ 'body' => 'blah' })
+    end
+
+    it "can be explicitly set" do
+      params = ActionController::Parameters.new({ action: 'update', post: { title: 'Hello', body: "blah", votes: 5, admin: true } })
+
+      expect(Controller.new(user, params).permitted_attributes(post, :revise)).to eq({ 'body' => 'blah' })
+    end
+  end
+
   describe "Pundit::NotAuthorizedError" do
     it "can be initialized with a string as message" do
       error = Pundit::NotAuthorizedError.new("must be logged in")

spec/spec_helper.rb

@@ -42,6 +42,10 @@ class PostPolicy < Struct.new(:user, :post)
       [:votes]
     end
   end
+
+  def permitted_attributes_for_revise
+    [:body]
+  end
 end
 class PostPolicy::Scope < Struct.new(:user, :scope)
   def resolve