Introduce .ruby-lsp.yml config file

lib/ruby_indexer/lib/ruby_indexer/configuration.rb

@@ -45,16 +45,20 @@ def initialize
 
     sig { void }
     def load_config
-      return unless File.exist?(".index.yml")
+      config_file = if File.exist?(".ruby-lsp.yml")
+        ".ruby-lsp.yml"
+      elsif File.exist?(".index.yml") # previously used name. Add a deprecation warning?
+        ".index.yml"
+      end
 
-      config = YAML.parse_file(".index.yml")
-      return unless config
+      config = YAML.parse_file(config_file)
+      return unless config # TODO: why would this be nil?
 
       config_hash = config.to_ruby
       validate_config!(config_hash)
       apply_config(config_hash)
     rescue Psych::SyntaxError => e
-      raise e, "Syntax error while loading .index.yml configuration: #{e.message}"
+      raise e, "Syntax error while loading #{config_file} configuration: #{e.message}"
     end
 
     sig { returns(T::Array[IndexablePath]) }

lib/ruby_indexer/test/configuration_test.rb

@@ -20,6 +20,23 @@ def test_load_configuration_executes_configure_block
       assert(indexables.none? { |indexable| indexable.full_path == __FILE__ })
     end
 
+    def test_supports_older_index_configuration
+      FileUtils.mv(".ruby-lsp.yml", ".ruby-lsp.yml.tmp")
+      s = <<~YAML
+        excluded_patterns:
+        - "**/test/fixtures/**/*.rb"
+      YAML
+      File.write(".index.yml", s)
+
+      @config.load_config
+      indexables = @config.indexables
+
+      assert(indexables.none? { |indexable| indexable.full_path.include?("test/fixtures") })
+    ensure
+      FileUtils.rm_f(".index.yml")
+      FileUtils.mv(".ruby-lsp.yml.tmp", ".ruby-lsp.yml")
+    end
+
     def test_indexables_only_includes_gem_require_paths
       @config.load_config
       indexables = @config.indexables