Merge pull request rails#50064 from Shopify/refactor-adapter-lookup

Author: byroot

activerecord/lib/active_record/connection_adapters.rb

@@ -4,6 +4,65 @@ module ActiveRecord
   module ConnectionAdapters
     extend ActiveSupport::Autoload
 
+    @adapters = {}
+
+    class << self
+      # Registers a custom database adapter.
+      #
+      # Can also be used to define aliases.
+      #
+      # == Example
+      #
+      #   ActiveRecord::ConnectionAdapters.register("megadb", "MegaDB::ActiveRecordAdapter", "mega_db/active_record_adapter")
+      #
+      #   ActiveRecord::ConnectionAdapters.register("mysql", "ActiveRecord::ConnectionAdapters::TrilogyAdapter", "active_record/connection_adapters/trilogy_adapter")
+      #
+      def register(name, class_name, path = class_name.underscore)
+        @adapters[name] = [class_name, path]
+      end
+
+      def resolve(adapter_name) # :nodoc:
+        # Require the adapter itself and give useful feedback about
+        #   1. Missing adapter gems and
+        #   2. Adapter gems' missing dependencies.
+        class_name, path_to_adapter = @adapters[adapter_name]
+
+        unless class_name
+          raise AdapterNotFound, "database configuration specifies nonexistent '#{adapter_name}' adapter. Ensure that the adapter is spelled correctly in config/database.yml and that you've added the necessary adapter gem to your Gemfile."
+        end
+
+        unless Object.const_defined?(class_name)
+          begin
+            require path_to_adapter
+          rescue LoadError => error
+            # We couldn't require the adapter itself. Raise an exception that
+            # points out config typos and missing gems.
+            if error.path == path_to_adapter
+              # We can assume that a non-builtin adapter was specified, so it's
+              # either misspelled or missing from Gemfile.
+              raise LoadError, "Error loading the '#{adapter_name}' Active Record adapter. Ensure that the necessary adapter gem is in the Gemfile. #{error.message}", error.backtrace
+
+              # Bubbled up from the adapter require. Prefix the exception message
+              # with some guidance about how to address it and reraise.
+            else
+              raise LoadError, "Error loading the '#{adapter_name}' Active Record adapter. Missing a gem it depends on? #{error.message}", error.backtrace
+            end
+          end
+        end
+
+        begin
+          Object.const_get(class_name)
+        rescue NameError => error
+          raise AdapterNotFound, "Could not load the #{class_name} Active Record adapter (#{error.message})."
+        end
+      end
+    end
+
+    register "sqlite3", "ActiveRecord::ConnectionAdapters::SQLite3Adapter", "active_record/connection_adapters/sqlite3_adapter"
+    register "mysql2", "ActiveRecord::ConnectionAdapters::Mysql2Adapter", "active_record/connection_adapters/mysql2_adapter"
+    register "trilogy", "ActiveRecord::ConnectionAdapters::TrilogyAdapter", "active_record/connection_adapters/trilogy_adapter"
+    register "postgresql", "ActiveRecord::ConnectionAdapters::PostgreSQLAdapter", "active_record/connection_adapters/postgresql_adapter"
+
     eager_autoload do
       autoload :AbstractAdapter
     end

activerecord/lib/active_record/connection_adapters/abstract/connection_handler.rb

@@ -324,32 +324,6 @@ def resolve_pool_config(config, connection_name, role, shard)
           db_config = Base.configurations.resolve(config)
 
           raise(AdapterNotSpecified, "database configuration does not specify adapter") unless db_config.adapter
-
-          # Require the adapter itself and give useful feedback about
-          #   1. Missing adapter gems and
-          #   2. Adapter gems' missing dependencies.
-          path_to_adapter = "active_record/connection_adapters/#{db_config.adapter}_adapter"
-          begin
-            require path_to_adapter
-          rescue LoadError => e
-            # We couldn't require the adapter itself. Raise an exception that
-            # points out config typos and missing gems.
-            if e.path == path_to_adapter
-              # We can assume that a non-builtin adapter was specified, so it's
-              # either misspelled or missing from Gemfile.
-              raise LoadError, "Could not load the '#{db_config.adapter}' Active Record adapter. Ensure that the adapter is spelled correctly in config/database.yml and that you've added the necessary adapter gem to your Gemfile.", e.backtrace
-
-              # Bubbled up from the adapter require. Prefix the exception message
-              # with some guidance about how to address it and reraise.
-            else
-              raise LoadError, "Error loading the '#{db_config.adapter}' Active Record adapter. Missing a gem it depends on? #{e.message}", e.backtrace
-            end
-          end
-
-          unless ActiveRecord::Base.respond_to?(db_config.adapter_method)
-            raise AdapterNotFound, "database configuration specifies nonexistent #{db_config.adapter} adapter"
-          end
-
           ConnectionAdapters::PoolConfig.new(connection_name, db_config, role, shard)
         end
 

activerecord/lib/active_record/connection_adapters/abstract/connection_pool.rb

@@ -682,7 +682,7 @@ def remove_connection_from_thread_cache(conn, owner_thread = conn.owner)
         alias_method :release, :remove_connection_from_thread_cache
 
         def new_connection
-          connection = Base.public_send(db_config.adapter_method, db_config.configuration_hash)
+          connection = db_config.new_connection
           connection.pool = self
           connection
         rescue ConnectionNotEstablished => ex

activerecord/lib/active_record/connection_adapters/mysql2_adapter.rb

@@ -7,17 +7,6 @@
 require "mysql2"
 
 module ActiveRecord
-  module ConnectionHandling # :nodoc:
-    def mysql2_adapter_class
-      ConnectionAdapters::Mysql2Adapter
-    end
-
-    # Establishes a connection to the database that's used by all Active Record objects.
-    def mysql2_connection(config)
-      mysql2_adapter_class.new(config)
-    end
-  end
-
   module ConnectionAdapters
     # = Active Record MySQL2 Adapter
     class Mysql2Adapter < AbstractMysqlAdapter

activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb

@@ -20,17 +20,6 @@
 require "active_record/connection_adapters/postgresql/utils"
 
 module ActiveRecord
-  module ConnectionHandling # :nodoc:
-    def postgresql_adapter_class
-      ConnectionAdapters::PostgreSQLAdapter
-    end
-
-    # Establishes a connection to the database that's used by all Active Record objects
-    def postgresql_connection(config)
-      postgresql_adapter_class.new(config)
-    end
-  end
-
   module ConnectionAdapters
     # = Active Record PostgreSQL Adapter
     #

activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb

@@ -15,16 +15,6 @@
 require "sqlite3"
 
 module ActiveRecord
-  module ConnectionHandling # :nodoc:
-    def sqlite3_adapter_class
-      ConnectionAdapters::SQLite3Adapter
-    end
-
-    def sqlite3_connection(config)
-      sqlite3_adapter_class.new(config)
-    end
-  end
-
   module ConnectionAdapters # :nodoc:
     # = Active Record SQLite3 Adapter
     #

activerecord/lib/active_record/connection_adapters/trilogy_adapter.rb

@@ -8,23 +8,6 @@
 require "active_record/connection_adapters/trilogy/database_statements"
 
 module ActiveRecord
-  module ConnectionHandling # :nodoc:
-    def trilogy_adapter_class
-      ConnectionAdapters::TrilogyAdapter
-    end
-
-    # Establishes a connection to the database that's used by all Active Record objects.
-    def trilogy_connection(config)
-      configuration = config.dup
-
-      # Set FOUND_ROWS capability on the connection so UPDATE queries returns number of rows
-      # matched rather than number of rows updated.
-      configuration[:found_rows] = true
-
-      trilogy_adapter_class.new(configuration)
-    end
-  end
-
   module ConnectionAdapters
     class TrilogyAdapter < AbstractMysqlAdapter
       ER_BAD_DB_ERROR = 1049
@@ -90,6 +73,16 @@ def initialize_type_map(m)
           end
       end
 
+      def initialize(config, *)
+        config = config.dup
+
+        # Set FOUND_ROWS capability on the connection so UPDATE queries returns number of rows
+        # matched rather than number of rows updated.
+        config[:found_rows] = true
+
+        super
+      end
+
       TYPE_MAP = Type::TypeMap.new.tap { |m| initialize_type_map(m) }
 
       def supports_json?

activerecord/lib/active_record/database_configurations/database_config.rb

@@ -8,17 +8,24 @@ class DatabaseConfigurations
     class DatabaseConfig # :nodoc:
       attr_reader :env_name, :name
 
+      def self.new(...)
+        instance = super
+        instance.adapter_class # Ensure resolution happens early
+        instance
+      end
+
       def initialize(env_name, name)
         @env_name = env_name
         @name = name
+        @adapter_class = nil
       end
 
-      def adapter_method
-        "#{adapter}_connection"
+      def adapter_class
+        @adapter_class ||= ActiveRecord::ConnectionAdapters.resolve(adapter)
       end
 
-      def adapter_class_method
-        "#{adapter}_adapter_class"
+      def new_connection
+        adapter_class.new(configuration_hash)
       end
 
       def host

activerecord/lib/active_record/database_configurations/hash_config.rb

@@ -104,7 +104,7 @@ def idle_timeout
       end
 
       def adapter
-        configuration_hash[:adapter]
+        configuration_hash[:adapter]&.to_s
       end
 
       # The path to the schema cache dump file for a database.