feat: add InMemoryProvider context callbacks and event emission (#224)

Signed-off-by: Jose Colella <jose.colella@gusto.com>
Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: josecolella

lib/open_feature/sdk/provider/in_memory_provider.rb

@@ -3,8 +3,9 @@
 module OpenFeature
   module SDK
     module Provider
-      # TODO: Add evaluation context support
       class InMemoryProvider
+        include Provider::EventEmitter
+
         NAME = "In-memory Provider"
 
         attr_reader :metadata
@@ -24,7 +25,12 @@ def shutdown
 
         def add_flag(flag_key:, value:)
           flags[flag_key] = value
-          # TODO: Emit PROVIDER_CONFIGURATION_CHANGED event once events are implemented
+          emit_provider_changed([flag_key])
+        end
+
+        def update_flags(new_flags)
+          @flags = new_flags.dup
+          emit_provider_changed(new_flags.keys)
         end
 
         def fetch_boolean_value(flag_key:, default_value:, evaluation_context: nil)
@@ -56,13 +62,24 @@ def fetch_object_value(flag_key:, default_value:, evaluation_context: nil)
         attr_reader :flags
 
         def fetch_value(flag_key:, default_value:, evaluation_context:)
-          value = flags[flag_key]
+          raw_value = flags[flag_key]
 
-          if value.nil?
+          if raw_value.nil?
             return ResolutionDetails.new(value: default_value, error_code: ErrorCode::FLAG_NOT_FOUND, reason: Reason::ERROR)
           end
 
-          ResolutionDetails.new(value:, reason: Reason::STATIC)
+          if raw_value.respond_to?(:call)
+            value = raw_value.call(evaluation_context)
+            ResolutionDetails.new(value: value, reason: Reason::TARGETING_MATCH)
+          else
+            ResolutionDetails.new(value: raw_value, reason: Reason::STATIC)
+          end
+        end
+
+        def emit_provider_changed(flag_keys)
+          return unless configuration_attached?
+
+          emit_event(ProviderEvent::PROVIDER_CONFIGURATION_CHANGED, flags_changed: flag_keys)
         end
       end
     end

spec/open_feature/sdk/provider/in_memory_provider_spec.rb

@@ -35,6 +35,94 @@
         expect(fetched.value).to eq(false)
       end
     end
+
+    context "when attached to configuration" do
+      it "emits PROVIDER_CONFIGURATION_CHANGED event" do
+        config = instance_double("OpenFeature::SDK::Configuration")
+        allow(config).to receive(:dispatch_provider_event)
+        provider.send(:attach, config)
+
+        provider.add_flag(flag_key: "new_flag", value: "new_value")
+
+        expect(config).to have_received(:dispatch_provider_event).with(
+          provider,
+          OpenFeature::SDK::ProviderEvent::PROVIDER_CONFIGURATION_CHANGED,
+          flags_changed: ["new_flag"]
+        )
+      end
+    end
+
+    context "when not attached to configuration" do
+      it "does not emit events" do
+        expect { provider.add_flag(flag_key: "new_flag", value: "new_value") }.not_to raise_error
+      end
+    end
+  end
+
+  describe "#update_flags" do
+    it "replaces all flags" do
+      provider.update_flags({"new_key" => "new_value"})
+
+      fetched = provider.fetch_string_value(flag_key: "new_key", default_value: "fallback")
+      expect(fetched.value).to eq("new_value")
+
+      old_fetched = provider.fetch_string_value(flag_key: "str", default_value: "fallback")
+      expect(old_fetched.value).to eq("fallback")
+      expect(old_fetched.error_code).to eq(OpenFeature::SDK::Provider::ErrorCode::FLAG_NOT_FOUND)
+    end
+
+    context "when attached to configuration" do
+      it "emits PROVIDER_CONFIGURATION_CHANGED event with all flag keys" do
+        config = instance_double("OpenFeature::SDK::Configuration")
+        allow(config).to receive(:dispatch_provider_event)
+        provider.send(:attach, config)
+
+        provider.update_flags({"flag_a" => true, "flag_b" => false})
+
+        expect(config).to have_received(:dispatch_provider_event).with(
+          provider,
+          OpenFeature::SDK::ProviderEvent::PROVIDER_CONFIGURATION_CHANGED,
+          flags_changed: contain_exactly("flag_a", "flag_b")
+        )
+      end
+    end
+
+    context "when not attached to configuration" do
+      it "does not emit events" do
+        expect { provider.update_flags({"flag_a" => true}) }.not_to raise_error
+      end
+    end
+  end
+
+  describe "context callbacks (callable flag values)" do
+    it "calls a Proc flag value with evaluation_context" do
+      context = OpenFeature::SDK::EvaluationContext.new(targeting_key: "user-123")
+      flag_proc = proc { |ctx| ctx.targeting_key == "user-123" }
+      provider = described_class.new({"dynamic_flag" => flag_proc})
+
+      fetched = provider.fetch_boolean_value(flag_key: "dynamic_flag", default_value: false, evaluation_context: context)
+
+      expect(fetched.value).to eq(true)
+      expect(fetched.reason).to eq(OpenFeature::SDK::Provider::Reason::TARGETING_MATCH)
+    end
+
+    it "calls a lambda flag value with evaluation_context" do
+      context = OpenFeature::SDK::EvaluationContext.new(targeting_key: "user-456")
+      flag_lambda = ->(ctx) { "hello-#{ctx.targeting_key}" }
+      provider = described_class.new({"greeting" => flag_lambda})
+
+      fetched = provider.fetch_string_value(flag_key: "greeting", default_value: "default", evaluation_context: context)
+
+      expect(fetched.value).to eq("hello-user-456")
+      expect(fetched.reason).to eq(OpenFeature::SDK::Provider::Reason::TARGETING_MATCH)
+    end
+
+    it "returns STATIC reason for non-callable values" do
+      fetched = provider.fetch_string_value(flag_key: "str", default_value: "fallback")
+
+      expect(fetched.value).to eq("testing")
+      expect(fetched.reason).to eq(OpenFeature::SDK::Provider::Reason::STATIC)
+    end
   end
 
   describe "#fetch_boolean_value" do

spec/open_feature/sdk/provider_compatibility_spec.rb

@@ -32,9 +32,9 @@
       expect { provider.shutdown }.not_to raise_error
     end
 
-    it "does not automatically gain event capabilities" do
-      expect(provider).not_to respond_to(:attach)
-      expect(provider).not_to respond_to(:emit_event)
+    it "has event capabilities via EventEmitter" do
+      expect(provider).to respond_to(:emit_event)
+      expect(provider).to respond_to(:configuration_attached?)
     end
 
     it "fetch methods continue to work" do
@@ -63,13 +63,6 @@
 end
 
 RSpec.describe "Provider Interface Detection" do
-  # Create a test provider that implements the new interfaces
-  let(:event_capable_provider) do
-    Class.new(OpenFeature::SDK::Provider::InMemoryProvider) do
-      include OpenFeature::SDK::Provider::EventEmitter
-    end.new
-  end
-
   it "can check if provider implements lifecycle methods using duck typing" do
     noop_provider = OpenFeature::SDK::Provider::NoOpProvider.new
     inmemory_provider = OpenFeature::SDK::Provider::InMemoryProvider.new
@@ -81,9 +74,10 @@
 
   it "can check if provider implements EventEmitter" do
     noop_provider = OpenFeature::SDK::Provider::NoOpProvider.new
+    inmemory_provider = OpenFeature::SDK::Provider::InMemoryProvider.new
 
     # Check using is_a? with module
     expect(noop_provider.class.included_modules).not_to include(OpenFeature::SDK::Provider::EventEmitter)
-    expect(event_capable_provider.class.included_modules).to include(OpenFeature::SDK::Provider::EventEmitter)
+    expect(inmemory_provider.class.included_modules).to include(OpenFeature::SDK::Provider::EventEmitter)
   end
 end