Add definition and hover support for :through associations

lib/ruby_lsp/ruby_lsp_rails/definition.rb

@@ -80,7 +80,7 @@ def handle_possible_dsl(node)
         return unless arguments
 
         if Support::Associations::ALL.include?(message)
-          handle_association(call_node)
+          handle_association(node, call_node)
         elsif Support::Callbacks::ALL.include?(message)
           handle_callback(node, call_node, arguments)
           handle_if_unless_conditional(node, call_node, arguments)
@@ -125,18 +125,57 @@ def handle_validation(node, call_node, arguments)
         collect_definitions(name)
       end
 
-      #: (Prism::CallNode node) -> void
-      def handle_association(node)
-        first_argument = node.arguments&.arguments&.first
-        return unless first_argument.is_a?(Prism::SymbolNode)
+      #: ((Prism::SymbolNode | Prism::StringNode) node, Prism::CallNode call_node) -> void
+      def handle_association(node, call_node)
+        arguments = call_node.arguments&.arguments
+        return unless arguments
+
+        first_argument = arguments.first
+        return unless first_argument.is_a?(Prism::SymbolNode) || first_argument.is_a?(Prism::StringNode)
+
+        association_name = extract_string_from_node(first_argument)
+        return unless association_name
+
+        through_element = find_through_association_element(arguments)
+        clicked_symbol = extract_string_from_node(node)
+        return unless clicked_symbol
+
+        if through_element
+          through_association_name = extract_string_from_node(through_element.value)
+
+          if clicked_symbol == association_name
+            handle_association_name(association_name)
+          elsif through_association_name && clicked_symbol == through_association_name
+            handle_association_name(through_association_name)
+          end
+        else
+          handle_association_name(association_name)
+        end
+      end
 
-        association_name = first_argument.unescaped
+      #: (Array[Prism::Node]) -> Prism::AssocNode?
+      def find_through_association_element(arguments)
+        result = arguments
+          .filter_map { |arg| arg.elements if arg.is_a?(Prism::KeywordHashNode) }
+          .flatten
+          .find do |elem|
+            next false unless elem.is_a?(Prism::AssocNode)
 
+            key = elem.key
+            next false unless key.is_a?(Prism::SymbolNode)
+
+            key.value == "through"
+          end
+
+        result if result.is_a?(Prism::AssocNode)
+      end
+
+      #: (String association_name) -> void
+      def handle_association_name(association_name)
         result = @client.association_target(
           model_name: @nesting.join("::"),
           association_name: association_name,
         )
-
         return unless result
 
         @response_builder << Support::LocationBuilder.line_location_from_s(result.fetch(:location))
@@ -194,6 +233,16 @@ def handle_if_unless_conditional(node, call_node, arguments)
 
         collect_definitions(method_name)
       end
+
+      #: (Prism::Node) -> String?
+      def extract_string_from_node(node)
+        case node
+        when Prism::SymbolNode
+          node.unescaped
+        when Prism::StringNode
+          node.content
+        end
+      end
     end
   end
 end

lib/ruby_lsp/ruby_lsp_rails/hover.rb

@@ -29,6 +29,7 @@ def initialize(client, response_builder, node_context, global_state, dispatcher)
           :on_constant_path_node_enter,
           :on_constant_read_node_enter,
           :on_symbol_node_enter,
+          :on_string_node_enter,
         )
       end
 
@@ -56,6 +57,11 @@ def on_symbol_node_enter(node)
         handle_possible_dsl(node)
       end
 
+      #: (Prism::StringNode node) -> void
+      def on_string_node_enter(node)
+        handle_possible_dsl(node)
+      end
+
       private
 
       #: (String name) -> void
@@ -116,28 +122,67 @@ def format_default(default_value, type)
         end
       end
 
-      #: (Prism::SymbolNode node) -> void
+      #: ((Prism::SymbolNode | Prism::StringNode) node) -> void
       def handle_possible_dsl(node)
-        node = @node_context.call_node
-        return unless node
-        return unless self_receiver?(node)
-
-        message = node.message
+        call_node = @node_context.call_node
+        return unless call_node
+        return unless self_receiver?(call_node)
 
+        message = call_node.message
         return unless message
 
         if Support::Associations::ALL.include?(message)
-          handle_association(node)
+          handle_association(node, call_node)
+        end
+      end
+
+      #: ((Prism::SymbolNode | Prism::StringNode) node, Prism::CallNode call_node) -> void
+      def handle_association(node, call_node)
+        arguments = call_node.arguments&.arguments
+        return unless arguments
+
+        first_argument = arguments.first
+        return unless first_argument.is_a?(Prism::SymbolNode) || first_argument.is_a?(Prism::StringNode)
+
+        association_name = extract_string_from_node(first_argument)
+        return unless association_name
+
+        through_element = find_through_association_element(arguments)
+        clicked_symbol = extract_string_from_node(node)
+        return unless clicked_symbol
+
+        if through_element
+          through_association_name = extract_string_from_node(through_element.value)
+
+          if clicked_symbol == association_name
+            handle_association_name(association_name)
+          elsif through_association_name && clicked_symbol == through_association_name
+            handle_association_name(through_association_name)
+          end
+        else
+          handle_association_name(association_name)
         end
       end
 
-      #: (Prism::CallNode node) -> void
-      def handle_association(node)
-        first_argument = node.arguments&.arguments&.first
-        return unless first_argument.is_a?(Prism::SymbolNode)
+      #: (Array[Prism::Node]) -> Prism::AssocNode?
+      def find_through_association_element(arguments)
+        result = arguments
+          .filter_map { |arg| arg.elements if arg.is_a?(Prism::KeywordHashNode) }
+          .flatten
+          .find do |elem|
+            next false unless elem.is_a?(Prism::AssocNode)
+
+            key = elem.key
+            next false unless key.is_a?(Prism::SymbolNode)
 
-        association_name = first_argument.unescaped
+            key.value == "through"
+          end
 
+        result if result.is_a?(Prism::AssocNode)
+      end
+
+      #: (String association_name) -> void
+      def handle_association_name(association_name)
         result = @client.association_target(
           model_name: @nesting.join("::"),
           association_name: association_name,
@@ -164,6 +209,16 @@ def generate_hover(name)
           @response_builder.push(content, category: category)
         end
       end
+
+      #: (Prism::Node) -> String?
+      def extract_string_from_node(node)
+        case node
+        when Prism::SymbolNode
+          node.unescaped
+        when Prism::StringNode
+          node.content
+        end
+      end
     end
   end
 end

test/dummy/app/models/country.rb

@@ -1,4 +1,5 @@
 # frozen_string_literal: true
 
 class Country < ApplicationRecord
+  has_one :flag, dependent: :destroy
 end

test/dummy/app/models/flag.rb

@@ -0,0 +1,5 @@
+# frozen_string_literal: true
+
+class Flag < ApplicationRecord
+  belongs_to :country
+end

test/dummy/app/models/user.rb

@@ -5,7 +5,8 @@ class User < ApplicationRecord
   validates :first_name, presence: true
   has_one :profile
   scope :adult, -> { where(age: 18..) }
-  has_one :location, class_name: "Country"
+  belongs_to :location, class_name: "Country"
+  has_one :country_flag, through: :location, source: :flag
 
   attr_readonly :last_name
 

test/dummy/db/migrate/20250703132109_create_flags.rb

@@ -0,0 +1,9 @@
+class CreateFlags < ActiveRecord::Migration[8.0]
+  def change
+    create_table :flags do |t|
+      t.references :country, null: false, foreign_key: true
+
+      t.timestamps
+    end
+  end
+end

test/dummy/db/schema.rb

@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[8.0].define(version: 2024_10_25_225348) do
+ActiveRecord::Schema[8.0].define(version: 2025_07_03_132109) do
   create_table "composite_primary_keys", primary_key: ["order_id", "product_id"], force: :cascade do |t|
     t.integer "order_id"
     t.integer "product_id"
@@ -25,6 +25,13 @@
     t.datetime "updated_at", null: false
   end
 
+  create_table "flags", force: :cascade do |t|
+    t.integer "country_id", null: false
+    t.datetime "created_at", null: false
+    t.datetime "updated_at", null: false
+    t.index ["country_id"], name: "index_flags_on_country_id"
+  end
+
   create_table "memberships", force: :cascade do |t|
     t.integer "user_id", null: false
     t.integer "organization_id", null: false
@@ -58,6 +65,7 @@
     t.index ["country_id"], name: "index_users_on_country_id"
   end
 
+  add_foreign_key "flags", "countries"
   add_foreign_key "memberships", "organizations"
   add_foreign_key "memberships", "users"
   add_foreign_key "users", "countries"