Add NamingStyle adapter to enforce format for added features.

examples/naming_style.rb

@@ -0,0 +1,19 @@
+require 'bundler/setup'
+require 'flipper'
+require 'flipper/adapters/naming_style'
+
+Flipper.configure do |config|
+  config.use Flipper::Adapters::NamingStyle, :snake # or :camel, :kebab, :screaming_snake, or a Regexp
+end
+
+# This will work because the feature key is in snake_case.
+Flipper.enable(:snake_case)
+
+begin
+  # This will raise an error because the feature key is in CamelCase.
+  Flipper.enable(:CamelCase)
+rescue Flipper::Adapters::NamingStyle::InvalidFormat => e
+  puts "#{e.class}: #{e.message}"
+else
+  fail "An error should have been raised, but wasn't."
+end

lib/flipper/adapters/naming_style.rb

@@ -0,0 +1,42 @@
+module Flipper
+  module Adapters
+    # An adapter that enforces a naming style for added features.
+    #
+    #   Flipper.configure do |config|
+    #     config.use Flipper::Adapters::NamingStyle, :snake # or :camel, :kebab, :screaming_snake, or a Regexp
+    #   end
+    #
+    class NamingStyle < Wrapper
+      InvalidFormat = Class.new(Flipper::Error)
+
+      PRESETS = {
+        camel: /^([A-Z][a-z0-9]*)+$/, # CamelCase
+        snake: /^[a-z0-9]+(_[a-z0-9]+)*$/, # snake_case
+        kebab: /^[a-z0-9]+(-[a-z0-9]+)*$/, # kebab-case
+        screaming_snake: /^[A-Z0-9]+(_[A-Z0-9]+)*$/, # SCREAMING_SNAKE_CASE
+      }
+
+      attr_reader :format
+
+      def initialize(adapter, format = :snake)
+        @format = format.is_a?(Regexp) ? format : PRESETS.fetch(format) {
+          raise ArgumentError, "Unknown format: #{format.inspect}. Must be a Regexp or one of #{PRESETS.keys.join(', ')}"
+        }
+
+        super(adapter)
+      end
+
+      def add(feature)
+        unless valid?(feature.key)
+          raise InvalidFormat, "Feature key #{feature.key.inspect} does not match format #{format.inspect}"
+        end
+
+        super feature
+      end
+
+      def valid?(name)
+        format.match?(name)
+      end
+    end
+  end
+end

spec/flipper/adapters/naming_style_spec.rb

@@ -0,0 +1,70 @@
+require "flipper/adapters/naming_style"
+
+RSpec.describe Flipper::Adapters::NamingStyle do
+  it_should_behave_like "a flipper adapter" do
+    let(:format) { /.*/ }
+    let(:memory) { Flipper::Adapters::Memory.new }
+    let(:adapter) { described_class.new(memory, format) }
+
+    subject { adapter }
+
+    describe "#initialize" do
+      it "accepts a regex" do
+        expect { described_class.new(memory, format) }.not_to raise_error
+      end
+
+      it "accepts a symbol" do
+        [:camel, :snake, :kebab, :screaming_snake].each do |format|
+          expect { described_class.new(memory, format) }.not_to raise_error
+        end
+      end
+
+      it "raises an error if the format is an unknown symbol" do
+        expect { described_class.new(memory, :Pascal) }.to raise_error(ArgumentError)
+      end
+    end
+
+    describe "#add" do
+      {
+        /\A(breaker|feature)\// => {
+          valid: %w[breaker/search feature/search],
+          invalid: %w[search breaker_search breaker],
+        },
+        camel: {
+          valid: %w[Camel CamelCase SCREAMINGCamelCase CamelCase1 Camel1Case],
+          invalid: %w[snake_case Camel-Kebab lowercase],
+        },
+        snake: {
+          valid: %w[lower snake_case snake_case_1],
+          invalid: %w[CamelCase cobraCase double__underscore],
+        },
+        kebab: {
+          valid: %w[kebab kebab-case kebab-case-1 htt-party],
+          invalid: %w[CamelCase CamelCase1 double__dash],
+        },
+        screaming_snake: {
+          valid: %w[SCREAMING SCREAMING_SNAKE SCREAMING_SNAKE_1 HTTP_THING],
+          invalid: %w[CamelCase CamelCase1 double__underscore],
+        }
+      }.each do |format, examples|
+        context "with format=#{format.inspect}" do
+          let(:format) { format }
+
+          examples[:valid].each do |feature|
+            it "adds feature named #{feature}" do
+              expect(subject.add(flipper[feature])).to eq(true)
+              expect(subject.features).to eq(Set[feature])
+            end
+          end
+
+          examples[:invalid].each do |feature|
+            it "raises an error for feature named #{feature}" do
+              expect { adapter.add(flipper[feature]) }.to raise_error(Flipper::Adapters::NamingStyle::InvalidFormat)
+              expect(subject.features).to eq(Set[])
+            end
+          end
+        end
+      end
+    end
+  end
+end