Use ConnectionBuilder instead of procs

spec/custom_drivers_types_spec.cr

@@ -36,6 +36,15 @@ class FooValue
 end
 
 class FooDriver < DB::Driver
+  class FooConnectionBuilder < DB::ConnectionBuilder
+    def initialize(@options : DB::Connection::Options)
+    end
+
+    def build : DB::Connection
+      FooConnection.new(@options)
+    end
+  end
+
   alias Any = DB::Any | FooValue
   @@row = [] of Any
 
@@ -47,10 +56,9 @@ class FooDriver < DB::Driver
     @@row
   end
 
-  def connection_builder(uri : URI) : Proc(DB::Connection)
+  def connection_builder(uri : URI) : DB::ConnectionBuilder
     params = HTTP::Params.parse(uri.query || "")
-    options = connection_options(params)
-    ->{ FooConnection.new(options).as(DB::Connection) }
+    FooConnectionBuilder.new(connection_options(params))
   end
 
   class FooConnection < DB::Connection
@@ -101,6 +109,15 @@ class BarValue
 end
 
 class BarDriver < DB::Driver
+  class BarConnectionBuilder < DB::ConnectionBuilder
+    def initialize(@options : DB::Connection::Options)
+    end
+
+    def build : DB::Connection
+      BarConnection.new(@options)
+    end
+  end
+
   alias Any = DB::Any | BarValue
   @@row = [] of Any
 
@@ -112,10 +129,9 @@ class BarDriver < DB::Driver
     @@row
   end
 
-  def connection_builder(uri : URI) : Proc(DB::Connection)
+  def connection_builder(uri : URI) : DB::ConnectionBuilder
     params = HTTP::Params.parse(uri.query || "")
-    options = connection_options(params)
-    ->{ BarConnection.new(options).as(DB::Connection) }
+    BarConnectionBuilder.new(connection_options(params))
   end
 
   class BarConnection < DB::Connection

spec/dummy_driver.cr

@@ -2,10 +2,18 @@ require "spec"
 require "../src/db"
 
 class DummyDriver < DB::Driver
-  def connection_builder(uri : URI) : Proc(DB::Connection)
+  class DummyConnectionBuilder < DB::ConnectionBuilder
+    def initialize(@options : DB::Connection::Options)
+    end
+
+    def build : DB::Connection
+      DummyConnection.new(@options)
+    end
+  end
+
+  def connection_builder(uri : URI) : DB::ConnectionBuilder
     params = HTTP::Params.parse(uri.query || "")
-    options = connection_options(params)
-    ->{ DummyConnection.new(options).as(DB::Connection) }
+    DummyConnectionBuilder.new(connection_options(params))
   end
 
   class DummyConnection < DB::Connection

src/db.cr

@@ -156,7 +156,8 @@ module DB
     params = HTTP::Params.parse(uri.query || "")
     connection_options = driver.connection_options(params)
     pool_options = driver.pool_options(params)
-    factory = driver.connection_builder(uri)
+    builder = driver.connection_builder(uri)
+    factory = ->{ builder.build }
     Database.new(connection_options, pool_options, &factory)
   end
 
@@ -165,7 +166,7 @@ module DB
   end
 
   private def self.build_connection(uri : URI)
-    build_driver(uri).connection_builder(uri).call
+    build_driver(uri).connection_builder(uri).build
   end
 
   private def self.build_driver(uri : URI)
@@ -193,6 +194,7 @@ require "./db/enumerable_concat"
 require "./db/query_methods"
 require "./db/session_methods"
 require "./db/disposable"
+require "./db/connection_builder"
 require "./db/driver"
 require "./db/statement"
 require "./db/begin_transaction"

src/db/connection_builder.cr

@@ -0,0 +1,8 @@
+module DB
+  # A connection factory with a specific configuration.
+  #
+  # See `Driver#connection_builder`.
+  abstract class ConnectionBuilder
+    abstract def build : Connection
+  end
+end

src/db/driver.cr

@@ -35,7 +35,7 @@ module DB
     #
     # NOTE: For implementors *uri* should be parsed once. If all the options
     # are sound a factory Proc is returned.
-    abstract def connection_builder(uri : URI) : Proc(Connection)
+    abstract def connection_builder(uri : URI) : ConnectionBuilder
 
     def connection_options(params : HTTP::Params) : Connection::Options
       Connection::Options.from_http_params(params)