Forbid sending undefined messages to ServiceActor::Result instances

CHANGELOG.md

@@ -11,6 +11,7 @@ Fixes:
 - Allow using a Hash as `default:` (#119)
 - Refactor `ServiceActor::Result` to get rid of `OpenStruct` inheritance
   (#127)
+- Deprecate invoking undefined methods on `ServiceActor::Result` (#129)
 - Ensure provided `failure_class` and `argument_error_class` values
   are subclasses of `Exception` (#132)
 - Skip `default` check for actor outputs (#135)

lib/service_actor/core.rb

@@ -15,6 +15,10 @@ def call(result = nil, **arguments)
       instance = new(result)
       instance._call
 
+      outputs.each_key do |key|
+        result.send("#{key}=", nil) unless result.respond_to?(key)
+      end
+
       result
     end
 

lib/service_actor/result.rb

@@ -74,18 +74,34 @@ def display
 
   attr_reader :data
 
-  def respond_to_missing?(_method_name, _include_private = false)
-    true
+  def respond_to_missing?(method_name, _include_private = false)
+    return true if method_name.end_with?("=")
+    return true if method_name.end_with?("?") && \
+                   data.key?(method_name.to_s.chomp("?").to_sym)
+    return true if data.key?(method_name)
+
+    false
   end
 
   def method_missing(method_name, *args) # rubocop:disable Metrics/AbcSize
-    if method_name.end_with?("?")
-      value = data[method_name.to_s.chomp("?").to_sym]
+    if method_name.end_with?("?") &&
+       data.key?(key = method_name.to_s.chomp("?").to_sym)
+      value = data[key]
       value.respond_to?(:empty?) ? !value.empty? : !!value
     elsif method_name.end_with?("=")
       data[method_name.to_s.chomp("=").to_sym] = args.first
-    else
+    elsif data.key?(method_name)
       data[method_name]
+    else
+      warn_on_undefined_method_invocation(method_name)
     end
   end
+
+  def warn_on_undefined_method_invocation(message)
+    Kernel.warn(
+      "DEPRECATED: Invoking undefined methods on `ServiceActor::Result` will " \
+      "lead to runtime errors in the next major release of Actor. " \
+      "Invoked method: `#{message}`",
+    )
+  end
 end

spec/actor_spec.rb

@@ -833,5 +833,35 @@
       it { expect(actor.name).to eq("Jim") }
       it { expect(actor.value).to eq(0) }
     end
+
+    context "with sending unexpected messages" do
+      let(:actor) { PlayActors.result(value: 42) }
+
+      before { allow(Kernel).to receive(:warn) }
+
+      it { expect(actor).to be_a_success }
+      it { expect(actor).to respond_to(:name) }
+      it { expect(actor).to respond_to(:name?) }
+      it { expect(actor.name).to eq("jim") }
+
+      it { expect(actor).not_to respond_to(:unknown_method) }
+      it { expect(actor).not_to respond_to(:unknown_method?) }
+
+      it "warns about sending unexpected messages" do
+        actor.unknown_method
+
+        expect(Kernel).to have_received(:warn).with(
+          include("unknown_method"),
+        )
+      end
+
+      it "warns about sending unexpected predicate messages" do
+        actor.unknown_method?
+
+        expect(Kernel).to have_received(:warn).with(
+          include("unknown_method?"),
+        )
+      end
+    end
   end
 end