Introduce .ruby-lsp.yml config file

.ruby-lsp.yml

@@ -0,0 +1,3 @@
+indexing:
+  excluded_patterns:
+    - "**/test/fixtures/**/*.rb"

README.md

@@ -68,6 +68,10 @@ See the [documentation](https://shopify.github.io/ruby-lsp) for more in-depth de
 For creating rich themes for Ruby using the semantic highlighting information, see the [semantic highlighting
 documentation](SEMANTIC_HIGHLIGHTING.md).
 
+## Configuration
+
+Configuration is read from an optional `.ruby-lsp.yml` file in the root of your project.
+
 ### Configuring code indexing
 
 By default, the Ruby LSP indexes all Ruby files defined in the current project and all of its dependencies, including
@@ -76,26 +80,30 @@ default gems, except for
 - Gems that only appear under the `:development` group
 - All Ruby files under `test/**/*.rb`
 
-By creating a `.index.yml` file, these configurations can be overridden and tuned. Note that indexing dependent behavior, such as definition, hover, completion or workspace symbol will be impacted by the configurations placed here.
+Within the `.ruby-lsp.yml` file, these configurations can be overridden and tuned. Note that indexing dependent behavior, such as definition, hover, completion or workspace symbol will be impacted by the configurations placed here.
 
 ```yaml
 # Exclude files based on a given pattern. Often used to exclude test files or fixtures
-excluded_patterns:
-  - "**/spec/**/*.rb"
+indexing:
+  excluded_patterns:
+    - "**/spec/**/*.rb"
 
 # Include files based on a given pattern. Can be used to index Ruby files that use different extensions
-included_patterns:
-  - "**/bin/*"
+indexing:
+  included_patterns:
+    - "**/bin/*"
 
 # Exclude gems by name. If a gem is never referenced in the project's code and is only used as a tool, excluding it will
 # speed up indexing and reduce the amount of results in features like definition or completion
-excluded_gems:
-  - rubocop
-  - pathname
+indexing:
+  excluded_gems:
+    - rubocop
+    - pathname
 
 # Include gems by name. Normally used to include development gems that are excluded by default
-included_gems:
-  - prism
+indexing:
+  included_gems:
+    - prism
 ```
 
 ### Addons

lib/ruby_indexer/lib/ruby_indexer/configuration.rb

@@ -45,16 +45,32 @@ def initialize
 
     sig { void }
     def load_config
-      return unless File.exist?(".index.yml")
+      config_file = if File.exist?(".ruby-lsp.yml")
+        warn("The .index.yml configuration file is deprecated. Please rename it to .ruby-lsp.yml and update the
+          structure as described in the README: https://github.com/Shopify/ruby-lsp?tab=readme-ov-file#configuration")
+        ".ruby-lsp.yml"
+      elsif File.exist?(".index.yml") # previously used for configuration
+        ".index.yml"
+      else
+        return
+      end
 
-      config = YAML.parse_file(".index.yml")
+      config = YAML.parse_file(config_file)
       return unless config
 
-      config_hash = config.to_ruby
+      config_hash = case config_file
+      when ".ruby-lsp.yml"
+        config.to_ruby["indexing"]
+      when ".index.yml"
+        config.to_ruby
+      else
+        raise "Invalid config file: #{config_file}" # Should never be reached
+      end
+
       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
@@ -101,8 +118,8 @@ def test_paths_are_unique
       assert_equal(indexables.uniq.length, indexables.length)
     end
 
-    def test_configuration_raises_for_unknown_keys
-      Psych::Nodes::Document.any_instance.expects(:to_ruby).returns({ "unknown_config" => 123 })
+    def test_configuration_raises_for_unknown_keys_within_indexing
+      Psych::Nodes::Document.any_instance.expects(:to_ruby).returns({ "indexing" => { "unknown_config" => 123 } })
 
       assert_raises(ArgumentError) do
         @config.load_config