add nested transaction with savepoints

spec/dummy_driver.cr

@@ -68,6 +68,29 @@ class DummyDriver < DB::Driver
       super
       @rolledback = true
     end
+
+    protected def create_save_point_transaction(parent, savepoint_name : String)
+      DummySavePointTransaction.new(parent, savepoint_name)
+    end
+  end
+
+  class DummySavePointTransaction < DB::SavePointTransaction
+    getter committed = false
+    getter rolledback = false
+
+    def initialize(parent, savepoint_name)
+      super(parent, savepoint_name)
+    end
+
+    def commit
+      super
+      @committed = true
+    end
+
+    def rollback
+      super
+      @rolledback = true
+    end
   end
 
   class DummyStatement < DB::Statement

spec/save_point_transaction_spec.cr

@@ -0,0 +1,127 @@
+require "./spec_helper"
+
+private class FooException < Exception
+end
+
+private def with_dummy_top_transaction
+  with_dummy_connection do |cnn|
+    cnn.transaction do |tx|
+      yield tx.as(DummyDriver::DummyTransaction), cnn
+    end
+  end
+end
+
+private def with_dummy_nested_transaction
+  with_dummy_connection do |cnn|
+    cnn.transaction do |tx|
+      tx.transaction do |nested|
+        yield nested.as(DummyDriver::DummySavePointTransaction), cnn
+      end
+    end
+  end
+end
+
+describe DB::SavePointTransaction do
+  {% for context in [:with_dummy_top_transaction, :with_dummy_nested_transaction] %}
+  describe "{{context.id}}" do
+    it "begin/commit transaction from parent transaction" do
+      {{context.id}} do |parent_tx|
+        tx = parent_tx.begin_transaction
+        tx.commit
+      end
+    end
+
+    it "begin/rollback transaction from parent transaction" do
+      {{context.id}} do |parent_tx|
+        tx = parent_tx.begin_transaction
+        tx.rollback
+      end
+    end
+
+    it "raise if begin over existing transaction" do
+      {{context.id}} do |parent_tx|
+        parent_tx.begin_transaction
+        expect_raises(DB::Error, "There is an existing nested transaction in this transaction") do
+          parent_tx.begin_transaction
+        end
+      end
+    end
+
+    it "allow sequential transactions" do
+      {{context.id}} do |parent_tx|
+        tx = parent_tx.begin_transaction
+        tx.rollback
+
+        tx = parent_tx.begin_transaction
+        tx.commit
+      end
+    end
+
+    it "transaction with block from parent transaction should be committed" do
+      t = uninitialized DummyDriver::DummySavePointTransaction
+
+      with_witness do |w|
+        {{context.id}} do |parent_tx|
+          parent_tx.transaction do |tx|
+            if tx.is_a?(DummyDriver::DummySavePointTransaction)
+              t = tx
+              w.check
+            end
+          end
+        end
+      end
+
+      t.committed.should be_true
+      t.rolledback.should be_false
+    end
+  end
+  {% end %}
+
+  it "only nested transaction with block from parent transaction should be rolledback if raise DB::Rollback" do
+    top = uninitialized DummyDriver::DummyTransaction
+    t = uninitialized DummyDriver::DummySavePointTransaction
+
+    with_witness do |w|
+      with_dummy_top_transaction do |parent_tx|
+        top = parent_tx
+        parent_tx.transaction do |tx|
+          if tx.is_a?(DummyDriver::DummySavePointTransaction)
+            t = tx
+            w.check
+          end
+          raise DB::Rollback.new
+        end
+      end
+    end
+
+    t.rolledback.should be_true
+    t.committed.should be_false
+
+    top.rolledback.should be_false
+    top.committed.should be_true
+  end
+
+  it "only nested transaction with block from parent nested transaction should be rolledback if raise DB::Rollback" do
+    top = uninitialized DummyDriver::DummySavePointTransaction
+    t = uninitialized DummyDriver::DummySavePointTransaction
+
+    with_witness do |w|
+      with_dummy_nested_transaction do |parent_tx|
+        top = parent_tx
+        parent_tx.transaction do |tx|
+          if tx.is_a?(DummyDriver::DummySavePointTransaction)
+            t = tx
+            w.check
+          end
+          raise DB::Rollback.new
+        end
+      end
+    end
+
+    t.rolledback.should be_true
+    t.committed.should be_false
+
+    top.rolledback.should be_false
+    top.committed.should be_true
+  end
+end