Don't treat begin and rollback transactions as write queries

Otherwise `save` method would raise the `ReadOnlyError` against `BEGIN`
and `ROLLBACK` queries.

2 files changed, 14 insertions, 3 deletions

diff --git a/activerecord/test/cases/base_test.rb b/activerecord/test/cases/base_test.rb
index b74bd93f37..11df74ea25 100644
--- a/activerecord/test/cases/base_test.rb
+++ b/activerecord/test/cases/base_test.rb
@@ -1490,31 +1490,37 @@ class BasicsTest < ActiveRecord::TestCase
   end
 
   test "creating a record raises if preventing writes" do
-    assert_raises ActiveRecord::ReadOnlyError do
+    error = assert_raises ActiveRecord::ReadOnlyError do
       ActiveRecord::Base.connection.while_preventing_writes do
         Bird.create! name: "Bluejay"
       end
     end
+
+    assert_match %r/\AWrite query attempted while in readonly mode: INSERT /, error.message
   end
 
   test "updating a record raises if preventing writes" do
     bird = Bird.create! name: "Bluejay"
 
-    assert_raises ActiveRecord::ReadOnlyError do
+    error = assert_raises ActiveRecord::ReadOnlyError do
       ActiveRecord::Base.connection.while_preventing_writes do
         bird.update! name: "Robin"
       end
     end
+
+    assert_match %r/\AWrite query attempted while in readonly mode: UPDATE /, error.message
   end
 
   test "deleting a record raises if preventing writes" do
     bird = Bird.create! name: "Bluejay"
 
-    assert_raises ActiveRecord::ReadOnlyError do
+    error = assert_raises ActiveRecord::ReadOnlyError do
       ActiveRecord::Base.connection.while_preventing_writes do
         bird.destroy!
       end
     end
+
+    assert_match %r/\AWrite query attempted while in readonly mode: DELETE /, error.message
   end
 
   test "selecting a record does not raise if preventing writes" do
diff --git a/activerecord/test/models/bird.rb b/activerecord/test/models/bird.rb
index be08636ac6..cfefa555b3 100644
--- a/activerecord/test/models/bird.rb
+++ b/activerecord/test/models/bird.rb
@@ -6,6 +6,11 @@ class Bird < ActiveRecord::Base
 
   accepts_nested_attributes_for :pirate
 
+  before_save do
+    # force materialize_transactions
+    self.class.connection.materialize_transactions
+  end
+
   attr_accessor :cancel_save_from_callback
   before_save :cancel_save_callback_method, if: :cancel_save_from_callback
   def cancel_save_callback_method