Add completion support

README.md

@@ -65,6 +65,10 @@ This extension supports the folowiing types of symbols:
 
 ![demo](images/document-symbol.gif)
 
+### Completion (experimental)
+
+Provides completion items for constant names and method names.
+
 ### Signature help (experimental)
 
 Shows method signature help when you start to type method arguments like `"100".to_i(`.

lib/rucoa/configuration.rb

@@ -11,6 +11,11 @@ def disable_code_action
       disable_feature('codeAction')
     end
 
+    # @return [void]
+    def disable_completion
+      disable_feature('completion')
+    end
+
     # @return [void]
     def disable_diagnostics
       disable_feature('diagnostics')
@@ -67,6 +72,11 @@ def enables_code_action?
       enables_feature?('codeAction')
     end
 
+    # @return [Boolean]
+    def enables_completion?
+      enables_feature?('completion')
+    end
+
     # @return [Boolean]
     def enables_diagnostics?
       enables_feature?('diagnostics')

lib/rucoa/handlers.rb

@@ -8,6 +8,7 @@ module Handlers
     autoload :InitializedHandler, 'rucoa/handlers/initialized_handler'
     autoload :ShutdownHandler, 'rucoa/handlers/shutdown_handler'
     autoload :TextDocumentCodeActionHandler, 'rucoa/handlers/text_document_code_action_handler'
+    autoload :TextDocumentCompletionHandler, 'rucoa/handlers/text_document_completion_handler'
     autoload :TextDocumentDidChangeHandler, 'rucoa/handlers/text_document_did_change_handler'
     autoload :TextDocumentDidOpenHandler, 'rucoa/handlers/text_document_did_open_handler'
     autoload :TextDocumentDocumentSymbolHandler, 'rucoa/handlers/text_document_document_symbol_handler'

lib/rucoa/handlers/initialize_handler.rb

@@ -7,6 +7,12 @@ def call
         respond(
           capabilities: {
             codeActionProvider: true,
+            completionProvider: {
+              resolveProvider: true,
+              triggerCharacters: %w[
+                .
+              ]
+            },
             documentFormattingProvider: true,
             documentRangeFormattingProvider: true,
             documentSymbolProvider: true,

lib/rucoa/handlers/text_document_completion_handler.rb

@@ -0,0 +1,216 @@
+# frozen_string_literal: true
+
+module Rucoa
+  module Handlers
+    class TextDocumentCompletionHandler < Base
+      COMPLETION_ITEM_KIND_FOR_TEXT = 1
+      COMPLETION_ITEM_KIND_FOR_METHOD = 2
+      COMPLETION_ITEM_KIND_FOR_FUNCTION = 3
+      COMPLETION_ITEM_KIND_FOR_CONSTRUCTOR = 4
+      COMPLETION_ITEM_KIND_FOR_FIELD = 5
+      COMPLETION_ITEM_KIND_FOR_VARIABLE = 6
+      COMPLETION_ITEM_KIND_FOR_CLASS = 7
+      COMPLETION_ITEM_KIND_FOR_INTERFACE = 8
+      COMPLETION_ITEM_KIND_FOR_MODULE = 9
+      COMPLETION_ITEM_KIND_FOR_PROPERTY = 10
+      COMPLETION_ITEM_KIND_FOR_UNIT = 11
+      COMPLETION_ITEM_KIND_FOR_VALUE = 12
+      COMPLETION_ITEM_KIND_FOR_ENUM = 13
+      COMPLETION_ITEM_KIND_FOR_KEYWORD = 14
+      COMPLETION_ITEM_KIND_FOR_SNIPPET = 15
+      COMPLETION_ITEM_KIND_FOR_COLOR = 16
+      COMPLETION_ITEM_KIND_FOR_FILE = 17
+      COMPLETION_ITEM_KIND_FOR_REFERENCE = 18
+      COMPLETION_ITEM_KIND_FOR_FOLDER = 19
+      COMPLETION_ITEM_KIND_FOR_ENUM_MEMBER = 20
+      COMPLETION_ITEM_KIND_FOR_CONSTANT = 21
+      COMPLETION_ITEM_KIND_FOR_STRUCT = 22
+      COMPLETION_ITEM_KIND_FOR_EVENT = 23
+      COMPLETION_ITEM_KIND_FOR_OPERATOR = 24
+      COMPLETION_ITEM_KIND_FOR_TYPE_PARAMETER = 25
+
+      EXAMPLE_IDENTIFIER = 'a'
+      private_constant :EXAMPLE_IDENTIFIER
+
+      def call
+        respond(completion_items)
+      end
+
+      private
+
+      # @return [Array<Hash>, nil]
+      def completion_items
+        return unless responsible?
+
+        case node
+        when Nodes::ConstNode
+          completion_items_for_constant
+        when Nodes::SendNode
+          if node.location.dot&.is?('::')
+            completion_items_for_constant
+          else
+            completion_items_for_method
+          end
+        else
+          []
+        end
+      end
+
+      # @return [Boolean]
+      def responsible?
+        configuration.enables_completion? &&
+          !source.nil?
+      end
+
+      # @return [Rucoa::Source, nil]
+      def source
+        @source ||= source_store.get(uri)
+      end
+
+      # @return [Rucoa::Position]
+      def position
+        @position ||= Position.from_vscode_position(
+          request.dig('params', 'position')
+        )
+      end
+
+      # @return [String]
+      def uri
+        request.dig('params', 'textDocument', 'uri')
+      end
+
+      # @return [Array<Hash>]
+      def completion_items_for_method
+        completable_method_names.map do |method_name|
+          {
+            kind: COMPLETION_ITEM_KIND_FOR_METHOD,
+            label: method_name,
+            textEdit: {
+              newText: method_name,
+              range: range.to_vscode_range
+            }
+          }
+        end
+      end
+
+      # @return [Array<Hash>]
+      def completion_items_for_constant
+        completable_constant_names.map do |constant_name|
+          {
+            kind: COMPLETION_ITEM_KIND_FOR_CONSTANT,
+            label: constant_name,
+            textEdit: {
+              newText: constant_name,
+              range: range.to_vscode_range
+            }
+          }
+        end
+      end
+
+      # @return [Array<String>]
+      def completable_constant_names
+        referrable_constant_names.select do |constant_name|
+          constant_name.start_with?(completion_head)
+        end.sort
+      end
+
+      # @return [String] e.g. "SE" to `File::SE|`, "ba" to `foo.ba|`
+      def completion_head
+        @completion_head ||=
+          if @repaired
+            ''
+          else
+            node.name
+          end
+      end
+
+      def referrable_constant_names
+        definition_store.constant_definitions_under(constant_namespace).map(&:name).uniq
+      end
+
+      # @return [String] e.g. "Foo::Bar" to `Foo::Bar.baz|`.
+      def constant_namespace
+        node.each_child_node(:const).map(&:name).reverse.join('::')
+      end
+
+      # @return [Array<String>]
+      def completable_method_names
+        callable_method_names.select do |method_name|
+          method_name.start_with?(completion_head)
+        end.sort
+      end
+
+      # @return [Array<String>]
+      def callable_method_names
+        callable_method_definitions.map(&:method_name).uniq
+      end
+
+      # @return [Array<String>]
+      def callable_method_definitions
+        receiver_types.flat_map do |type|
+          definition_store.method_definitions_of(type)
+        end
+      end
+
+      # @return [Array<String>]
+      def receiver_types
+        NodeInspector.new(
+          definition_store: definition_store,
+          node: node
+        ).method_receiver_types
+      end
+
+      # @return [Rucoa::Node, nil]
+      def node
+        @node ||=
+          if source.syntax_error?
+            repair
+            repaired_node
+          else
+            normal_node
+          end
+      end
+
+      # @return [Rucoa::Node, nil]
+      def normal_node
+        source.node_at(position)
+      end
+
+      # @return [Rucoa::Node, nil]
+      def repaired_node
+        repaired_source.node_at(position)
+      end
+
+      # @return [void]
+      def repair
+        @repaired = true
+      end
+
+      # @return [String]
+      def repaired_content
+        source.content.dup.insert(
+          position.to_index_of(source.content),
+          EXAMPLE_IDENTIFIER
+        )
+      end
+
+      # @return [Rucoa::Source]
+      def repaired_source
+        Source.new(
+          content: repaired_content,
+          uri: source.uri
+        )
+      end
+
+      # @return [Rucoa::Range]
+      def range
+        @range ||=
+          if @repaired
+            position.to_range
+          else
+            Range.from_parser_range(node.location.expression)
+          end
+      end
+    end
+  end
+end

lib/rucoa/position.rb

@@ -44,6 +44,17 @@ def initialize(column:, line:)
       @line = line
     end
 
+    # @param text [String]
+    # @return [Integer]
+    def to_index_of(text)
+      text.each_line.take(@line - 1).sum(&:length) + @column
+    end
+
+    # @return [Rucoa::Range]
+    def to_range
+      Range.new(self, self)
+    end
+
     # @return [Hash]
     def to_vscode_position
       {

lib/rucoa/server.rb

@@ -12,6 +12,7 @@ class Server
       'initialized' => Handlers::InitializedHandler,
       'shutdown' => Handlers::ShutdownHandler,
       'textDocument/codeAction' => Handlers::TextDocumentCodeActionHandler,
+      'textDocument/completion' => Handlers::TextDocumentCompletionHandler,
       'textDocument/didChange' => Handlers::TextDocumentDidChangeHandler,
       'textDocument/didOpen' => Handlers::TextDocumentDidOpenHandler,
       'textDocument/documentSymbol' => Handlers::TextDocumentDocumentSymbolHandler,

lib/rucoa/source.rb

@@ -78,6 +78,11 @@ def root_node
       nil
     end
 
+    # @return [Boolean]
+    def syntax_error?
+      root_node.nil?
+    end
+
     private
 
     # @return [Array<Rucoa::Nodes::Base>]