fix: Add additional payload filter key validation

contract-tests/service.rb

@@ -31,6 +31,7 @@
       'all-flags-client-side-only',
       'all-flags-details-only-for-tracked-flags',
       'filtering',
+      'filtering-strict',
       'secure-mode-hash',
       'tags',
       'migrations',

launchdarkly-server-sdk.gemspec

@@ -22,6 +22,7 @@ Gem::Specification.new do |spec|
   spec.required_ruby_version = ">= 3.0.0"
 
   spec.add_development_dependency "aws-sdk-dynamodb", "~> 1.57"
+  spec.add_development_dependency "rexml", "~> 3.3", ">= 3.3.7"
   spec.add_development_dependency "bundler", "2.2.33"
   spec.add_development_dependency "simplecov", "~> 0.21"
   spec.add_development_dependency "rspec", "~> 3.10"

lib/ldclient-rb/config.rb

@@ -77,7 +77,7 @@ def initialize(opts = {})
       @socket_factory = opts[:socket_factory]
       @big_segments = opts[:big_segments] || BigSegmentsConfig.new(store: nil)
       @application = LaunchDarkly::Impl::Util.validate_application_info(opts[:application] || {}, @logger)
-      @payload_filter_key = opts[:payload_filter_key]
+      @payload_filter_key = LaunchDarkly::Impl::Util.validate_payload_filter_key(opts[:payload_filter_key] , @logger)
       @hooks = (opts[:hooks] || []).keep_if { |hook| hook.is_a? Interfaces::Hooks::Hook }
       @omit_anonymous_contexts = opts.has_key?(:omit_anonymous_contexts) && opts[:omit_anonymous_contexts]
       @data_source_update_sink = nil

lib/ldclient-rb/impl/util.rb

@@ -75,6 +75,21 @@ def self.validate_application_info(app, logger)
           version: validate_application_value(app[:version], :version, logger),
         }
       end
+
+      #
+      # @param value [String, nil]
+      # @param logger [Logger]
+      # @return [String, nil]
+      #
+      def self.validate_payload_filter_key(value, logger)
+        return nil if value.nil?
+        return value if value.is_a?(String) && /^[a-zA-Z0-9][._\-a-zA-Z0-9]*$/.match?(value)
+
+        logger.warn {
+          "Invalid payload filter configured, full environment will be fetched. Ensure the filter key is not empty and was copied correctly from LaunchDarkly settings."
+        }
+        nil
+      end
     end
   end
 end

lib/ldclient-rb/util.rb

@@ -77,11 +77,6 @@ module Util
     def self.add_payload_filter_key(uri, config)
       return uri if config.payload_filter_key.nil?
 
-      unless config.payload_filter_key.is_a?(String) && !config.payload_filter_key.empty?
-        config.logger.warn { "[LDClient] Filter key must be a non-empty string. No filtering will be applied." }
-        return uri
-      end
-
       begin
         parsed = URI.parse(uri)
         new_query_params = URI.decode_www_form(String(parsed.query)) << ["filter", config.payload_filter_key]

spec/impl/util_spec.rb

@@ -0,0 +1,52 @@
+require "spec_helper"
+
+module LaunchDarkly
+  module Impl
+    describe "payload filter key validation" do
+      let(:logger) { double }
+
+      it "silently discards nil" do
+        expect(logger).not_to receive(:warn)
+        expect(Util.validate_payload_filter_key(nil, logger)).to be_nil
+      end
+
+      [true, 1, 1.0, [], {}].each do |value|
+        it "returns nil for invalid type #{value.class}" do
+          expect(logger).to receive(:warn)
+          expect(Util.validate_payload_filter_key(value, logger)).to be_nil
+        end
+      end
+
+      [
+        "",
+        "-cannot-start-with-dash",
+        "_cannot-start-with-underscore",
+        "-cannot-start-with-period",
+        "no spaces for you",
+        "org@special/characters",
+      ].each do |value|
+        it "returns nil for invalid value #{value}" do
+          expect(logger).to receive(:warn)
+          expect(Util.validate_payload_filter_key(value, logger)).to be_nil
+        end
+      end
+
+      [
+        "camelCase",
+        "snake_case",
+        "kebab-case",
+        "with.dots",
+        "with_underscores",
+        "with-hyphens",
+        "with1234numbers",
+        "with.many_1234-mixtures",
+        "1start-with-number",
+      ].each do |value|
+        it "passes for value #{value}" do
+          expect(logger).not_to receive(:warn)
+          expect(Util.validate_payload_filter_key(value, logger)).to eq(value)
+        end
+      end
+    end
+  end
+end