fix: Refactor new connection

The old method was calling `AbstractAdapter#initialize`
with a connection object, rather than a hash. This was
then setting `@unconfigured_connection`, which in turns
forced to re-run `#configure_connection` when a first
query was made. This is usually OK (although unnecessary)
except if `use_follower_reads_for_type_introspection` is
used, since it sets AOST for a single query, which fails
within a transaction.

Fixes #320

Gemfile

@@ -55,6 +55,7 @@ group :development, :test do
   gem "debug"
   gem "minitest-excludes", "~> 2.0.1"
   gem "minitest-github_action_reporter", github: "BuonOmo/minitest-github_action_reporter", require: "minitest/github_action_reporter_plugin"
+  gem "ostruct", "~> 0.6"
 
   # Gems used for tests meta-programming.
   gem "parser"

lib/active_record/connection_adapters/cockroachdb_adapter.rb

@@ -32,35 +32,15 @@
 ActiveRecord::ConnectionAdapters::CockroachDB.initial_setup
 
 module ActiveRecord
+  # TODO: once in rails 7.2, remove this and replace with a `#register` call.
+  # See: https://github.com/rails/rails/commit/22a26d7f74ea8f0d5f7c4169531ae38441cfd5e5#diff-2468c670eb10c24bd2823e42708489a336d6f21c6efc7e3c4a574166fa77bb22
   module ConnectionHandling
+    def cockroachdb_adapter_class
+      ConnectionAdapters::CockroachDBAdapter
+    end
+
     def cockroachdb_connection(config)
-      # This is copied from the PostgreSQL adapter.
-      conn_params = config.symbolize_keys.compact
-
-      # Map ActiveRecords param names to PGs.
-      conn_params[:user] = conn_params.delete(:username) if conn_params[:username]
-      conn_params[:dbname] = conn_params.delete(:database) if conn_params[:database]
-
-      # Forward only valid config params to PG::Connection.connect.
-      valid_conn_param_keys = PG::Connection.conndefaults_hash.keys + [:requiressl]
-      conn_params.slice!(*valid_conn_param_keys)
-
-      ConnectionAdapters::CockroachDBAdapter.new(
-        ConnectionAdapters::CockroachDBAdapter.new_client(conn_params),
-        logger,
-        conn_params,
-        config
-      )
-    # This rescue flow appears in new_client, but it is needed here as well
-    # since Cockroach will sometimes not raise until a query is made.
-    rescue ActiveRecord::StatementInvalid => error
-      no_db_err_check1 = conn_params && conn_params[:dbname] && error.cause.message.include?(conn_params[:dbname])
-      no_db_err_check2 = conn_params && conn_params[:dbname] && error.cause.message.include?("pg_type")
-      if no_db_err_check1 || no_db_err_check2
-        raise ActiveRecord::NoDatabaseError
-      else
-        raise ActiveRecord::ConnectionNotEstablished, error.message
-      end
+      cockroachdb_adapter_class.new(config)
     end
   end
 end
@@ -255,6 +235,21 @@ def self.database_exists?(config)
         false
       end
 
+      def initialize(...)
+        super
+
+      # This rescue flow appears in new_client, but it is needed here as well
+      # since Cockroach will sometimes not raise until a query is made.
+      rescue ActiveRecord::StatementInvalid => error
+        no_db_err_check1 = @connection_parameters && @connection_parameters[:dbname] && error.cause.message.include?(@connection_parameters[:dbname])
+        no_db_err_check2 = @connection_parameters && @connection_parameters[:dbname] && error.cause.message.include?("pg_type")
+        if no_db_err_check1 || no_db_err_check2
+          raise ActiveRecord::NoDatabaseError
+        else
+          raise ActiveRecord::ConnectionNotEstablished, error.message
+        end
+      end
+
       # override
       # The PostgreSQLAdapter uses syntax for an anonymous function
       # (DO $$) that CockroachDB does not support.