feat: adds InMemoryProvider (#102)

Signed-off-by: Max VelDink <maxveldink@gmail.com>

Gemfile.lock

@@ -9,8 +9,15 @@ GEM
     ast (2.4.2)
     base64 (0.1.1)
     concurrent-ruby (1.2.3)
+    debug (1.9.1)
+      irb (~> 1.10)
+      reline (>= 0.3.8)
     diff-lcs (1.5.0)
     docile (1.4.0)
+    io-console (0.7.2)
+    irb (1.11.2)
+      rdoc
+      reline (>= 0.4.2)
     json (2.6.3)
     language_server-protocol (3.17.0.3)
     lint_roller (1.1.0)
@@ -19,10 +26,16 @@ GEM
     parser (3.2.2.3)
       ast (~> 2.4.1)
       racc
+    psych (5.1.2)
+      stringio
     racc (1.7.1)
     rainbow (3.1.1)
     rake (13.0.6)
+    rdoc (6.6.2)
+      psych (>= 4.0.0)
     regexp_parser (2.8.1)
+    reline (0.4.3)
+      io-console (~> 0.5)
     rexml (3.2.6)
     rspec (3.12.0)
       rspec-core (~> 3.12.0)
@@ -76,6 +89,7 @@ GEM
     standard-performance (1.2.0)
       lint_roller (~> 1.1)
       rubocop-performance (~> 1.19.0)
+    stringio (3.1.0)
     unicode-display_width (2.4.2)
 
 PLATFORMS
@@ -91,6 +105,7 @@ PLATFORMS
 
 DEPENDENCIES
   concurrent-ruby
+  debug
   markly
   openfeature-sdk!
   rake (~> 13.0)

README.md

@@ -43,7 +43,12 @@ require 'json' # For JSON.dump
 
 OpenFeature::SDK.configure do |config|
     # your provider of choice
-    config.provider = OpenFeature::SDK::Provider::NoOpProvider.new
+    config.provider = OpenFeature::SDK::Provider::InMemoryProvider.new(
+      {
+        "flag1" => true,
+        "flag2" => 1
+      }
+    )
 end
 
 # Create a client
@@ -69,7 +74,7 @@ For complete documentation, visit: https://openfeature.dev/docs/category/concept
 
 Providers are the abstraction layer between OpenFeature and different flag management systems.
 
-The `NoOpProvider` is an example of a minimalist provider. For complete documentation on the Provider interface, visit: https://openfeature.dev/specification/sections/providers.
+The `NoOpProvider` is an example of a minimalist provider. The `InMemoryProvider` is a provider that can be initialized with flags and used to store flags in process. For complete documentation on the Provider interface, visit: https://openfeature.dev/specification/sections/providers.
 
 In addition to the `fetch_*` methods, providers can optionally implement lifecycle methods that are invoked when the underlying provider is switched out. For example:
 

lib/open_feature/sdk/provider.rb

@@ -2,6 +2,7 @@
 require_relative "provider/reason"
 require_relative "provider/resolution_details"
 require_relative "provider/no_op_provider"
+require_relative "provider/in_memory_provider"
 
 module OpenFeature
   module SDK

lib/open_feature/sdk/provider/in_memory_provider.rb

@@ -0,0 +1,62 @@
+module OpenFeature
+  module SDK
+    module Provider
+      # TODO: Add evaluation context support
+      class InMemoryProvider
+        NAME = "In-memory Provider"
+
+        def initialize(flags = {})
+          @metadata = Metadata.new(name: NAME).freeze
+          @flags = flags
+        end
+
+        def init
+          # Intentional no-op, used for testing
+        end
+
+        def shutdown
+          # Intentional no-op, used for testing
+        end
+
+        def add_flag(flag_key:, value:)
+          flags[flag_key] = value
+          # TODO: Emit PROVIDER_CONFIGURATION_CHANGED event once events are implemented
+        end
+
+        def fetch_boolean_value(flag_key:, default_value:, evaluation_context: nil)
+          fetch_value(allowed_classes: [TrueClass, FalseClass], flag_key:, default_value:, evaluation_context:)
+        end
+
+        def fetch_string_value(flag_key:, default_value:, evaluation_context: nil)
+          fetch_value(allowed_classes: [String], flag_key:, default_value:, evaluation_context:)
+        end
+
+        def fetch_number_value(flag_key:, default_value:, evaluation_context: nil)
+          fetch_value(allowed_classes: [Integer, Float], flag_key:, default_value:, evaluation_context:)
+        end
+
+        def fetch_object_value(flag_key:, default_value:, evaluation_context: nil)
+          fetch_value(allowed_classes: [Array, Hash], flag_key:, default_value:, evaluation_context:)
+        end
+
+        private
+
+        attr_reader :flags
+
+        def fetch_value(allowed_classes:, flag_key:, default_value:, evaluation_context:)
+          value = flags[flag_key]
+
+          if value.nil?
+            return ResolutionDetails.new(value: default_value, error_code: ErrorCode::FLAG_NOT_FOUND, reason: Reason::ERROR)
+          end
+
+          if allowed_classes.include?(value.class)
+            ResolutionDetails.new(value:, reason: Reason::STATIC)
+          else
+            ResolutionDetails.new(value: default_value, error_code: ErrorCode::TYPE_MISMATCH, reason: Reason::ERROR)
+          end
+        end
+      end
+    end
+  end
+end

openfeature-sdk.gemspec

@@ -31,6 +31,7 @@ Gem::Specification.new do |spec|
   spec.executables = spec.files.grep(%r{\Aexe/}) { |f| File.basename(f) }
   spec.require_paths = ["lib"]
 
+  spec.add_development_dependency "debug"
   spec.add_development_dependency "markly"
   spec.add_development_dependency "rake", "~> 13.0"
   spec.add_development_dependency "rspec", "~> 3.12.0"

spec/open_feature/sdk/configuration_spec.rb

@@ -7,7 +7,7 @@
 
   describe "#provider=" do
     context "when provider has an init method" do
-      let(:provider) { TestProvider.new }
+      let(:provider) { OpenFeature::SDK::Provider::InMemoryProvider.new }
 
       it "inits and sets the provider" do
         expect(provider).to receive(:init)

spec/open_feature/sdk/provider/in_memory_provider_spec.rb

@@ -0,0 +1,168 @@
+require "spec_helper"
+
+RSpec.describe OpenFeature::SDK::Provider::InMemoryProvider do
+  subject(:provider) do
+    described_class.new(
+      {
+        "bool" => true,
+        "str" => "testing",
+        "num" => 1,
+        "struct" => {"more" => "config"}
+      }
+    )
+  end
+
+  describe "#add_flag" do
+    context "when flag doesn't exist" do
+      it "adds flag" do
+        provider.add_flag(flag_key: "new_flag", value: "new_value")
+
+        fetched = provider.fetch_string_value(flag_key: "new_flag", default_value: "fallback")
+
+        expect(fetched.value).to eq("new_value")
+      end
+    end
+
+    context "when flag exists" do
+      it "updates flag" do
+        provider.add_flag(flag_key: "bool", value: false)
+
+        fetched = provider.fetch_boolean_value(flag_key: "bool", default_value: true)
+
+        expect(fetched.value).to eq(false)
+      end
+    end
+  end
+
+  describe "#fetch_boolean_value" do
+    context "when flag is found" do
+      context "when type matches" do
+        it "returns value as static" do
+          fetched = provider.fetch_boolean_value(flag_key: "bool", default_value: false)
+
+          expect(fetched.value).to eq(true)
+          expect(fetched.reason).to eq(OpenFeature::SDK::Provider::Reason::STATIC)
+        end
+      end
+
+      context "when type does not match" do
+        it "returns default as type mismatch" do
+          fetched = provider.fetch_boolean_value(flag_key: "str", default_value: false)
+
+          expect(fetched.value).to eq(false)
+          expect(fetched.error_code).to eq(OpenFeature::SDK::Provider::ErrorCode::TYPE_MISMATCH)
+          expect(fetched.reason).to eq(OpenFeature::SDK::Provider::Reason::ERROR)
+        end
+      end
+    end
+
+    context "when flag is not found" do
+      it "returns default as flag not found" do
+        fetched = provider.fetch_boolean_value(flag_key: "not here", default_value: false)
+
+        expect(fetched.value).to eq(false)
+        expect(fetched.error_code).to eq(OpenFeature::SDK::Provider::ErrorCode::FLAG_NOT_FOUND)
+        expect(fetched.reason).to eq(OpenFeature::SDK::Provider::Reason::ERROR)
+      end
+    end
+  end
+
+  describe "#fetch_string_value" do
+    context "when flag is found" do
+      context "when type matches" do
+        it "returns value as static" 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
+
+      context "when type does not match" do
+        it "returns default as type mismatch" do
+          fetched = provider.fetch_string_value(flag_key: "bool", default_value: "fallback")
+
+          expect(fetched.value).to eq("fallback")
+          expect(fetched.error_code).to eq(OpenFeature::SDK::Provider::ErrorCode::TYPE_MISMATCH)
+          expect(fetched.reason).to eq(OpenFeature::SDK::Provider::Reason::ERROR)
+        end
+      end
+    end
+
+    context "when flag is not found" do
+      it "returns default as flag not found" do
+        fetched = provider.fetch_string_value(flag_key: "not here", default_value: "fallback")
+
+        expect(fetched.value).to eq("fallback")
+        expect(fetched.error_code).to eq(OpenFeature::SDK::Provider::ErrorCode::FLAG_NOT_FOUND)
+        expect(fetched.reason).to eq(OpenFeature::SDK::Provider::Reason::ERROR)
+      end
+    end
+  end
+
+  describe "#fetch_number_value" do
+    context "when flag is found" do
+      context "when type matches" do
+        it "returns value as static" do
+          fetched = provider.fetch_number_value(flag_key: "num", default_value: 0)
+
+          expect(fetched.value).to eq(1)
+          expect(fetched.reason).to eq(OpenFeature::SDK::Provider::Reason::STATIC)
+        end
+      end
+
+      context "when type does not match" do
+        it "returns default as type mismatch" do
+          fetched = provider.fetch_number_value(flag_key: "str", default_value: 0)
+
+          expect(fetched.value).to eq(0)
+          expect(fetched.error_code).to eq(OpenFeature::SDK::Provider::ErrorCode::TYPE_MISMATCH)
+          expect(fetched.reason).to eq(OpenFeature::SDK::Provider::Reason::ERROR)
+        end
+      end
+    end
+
+    context "when flag is not found" do
+      it "returns default as flag not found" do
+        fetched = provider.fetch_number_value(flag_key: "not here", default_value: 0)
+
+        expect(fetched.value).to eq(0)
+        expect(fetched.error_code).to eq(OpenFeature::SDK::Provider::ErrorCode::FLAG_NOT_FOUND)
+        expect(fetched.reason).to eq(OpenFeature::SDK::Provider::Reason::ERROR)
+      end
+    end
+  end
+
+  describe "#fetch_object_value" do
+    context "when flag is found" do
+      context "when type matches" do
+        it "returns value as static" do
+          fetched = provider.fetch_object_value(flag_key: "struct", default_value: {})
+
+          expect(fetched.value).to eq({"more" => "config"})
+          expect(fetched.reason).to eq(OpenFeature::SDK::Provider::Reason::STATIC)
+        end
+      end
+
+      context "when type does not match" do
+        it "returns default as type mismatch" do
+          fetched = provider.fetch_object_value(flag_key: "num", default_value: {})
+
+          expect(fetched.value).to eq({})
+          expect(fetched.error_code).to eq(OpenFeature::SDK::Provider::ErrorCode::TYPE_MISMATCH)
+          expect(fetched.reason).to eq(OpenFeature::SDK::Provider::Reason::ERROR)
+        end
+      end
+    end
+
+    context "when flag is not found" do
+      it "returns default as flag not found" do
+        fetched = provider.fetch_object_value(flag_key: "not here", default_value: {})
+
+        expect(fetched.value).to eq({})
+        expect(fetched.error_code).to eq(OpenFeature::SDK::Provider::ErrorCode::FLAG_NOT_FOUND)
+        expect(fetched.reason).to eq(OpenFeature::SDK::Provider::Reason::ERROR)
+      end
+    end
+  end
+end

spec/spec_helper.rb

@@ -6,6 +6,8 @@
 
 require "markly"
 
+require "debug"
+
 RSpec.configure do |config|
   # Enable flags like --only-failures and --next-failure
   config.example_status_persistence_file_path = ".rspec_status"
@@ -17,6 +19,8 @@
     c.syntax = :expect
   end
 
+  config.filter_run_when_matching :focus
+
   # ie for GitHub Actions
   # see https://docs.github.com/en/actions/learn-github-actions/environment-variables#default-environment-variables
   if ENV["CI"] == "true"

spec/specification/flag_evaluation_api_spec.rb

@@ -1,7 +1,6 @@
 # frozen_string_literal: true
 
 require "spec_helper"
-require_relative "../support/test_provider"
 
 RSpec.describe "Flag Evaluation API" do
   context "1.1 - API Initialization and Configuration" do
@@ -23,7 +22,7 @@
 
     context "Requirement 1.1.2.2" do
       specify "the provider mutator must invoke an initialize function on the provider" do
-        provider = TestProvider.new
+        provider = OpenFeature::SDK::Provider::InMemoryProvider.new
         expect(provider).to receive(:init)
 
         OpenFeature::SDK.provider = provider
@@ -32,8 +31,8 @@
 
     context "Requirement 1.1.2.3" do
       specify "the provider mutator must invoke a shutdown function on previously registered provider" do
-        previous_provider = TestProvider.new
-        new_provider = TestProvider.new
+        previous_provider = OpenFeature::SDK::Provider::InMemoryProvider.new
+        new_provider = OpenFeature::SDK::Provider::InMemoryProvider.new
 
         expect(previous_provider).to receive(:shutdown)
         expect(new_provider).not_to receive(:shutdown)