Prevent calling a stabbed method within a transaction

With a new setting `within_transaction: false` you can prevent
calling a stabbed method within a database transaction.

```yaml
---
- class: Foo
  chain:
    - bar
    - baz
  within_transaction: false
  actions:
    - return: 0
```

If you call the method inside a transaction, the call will raise
an exception `::Isolator::UnsafeOperationError` pointing to
the method `Foo.bar.baz(*)`.

Notice that this setting is argument-specific. You can allow it
to be called inside a transaction with some arguments, and
<explicitly> forbid for some other arguments at the same time.

CHANGELOG.md

@@ -5,6 +5,40 @@ All notable changes to this project will be documented in this file.
 The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
+## 0.0.8 - WIP 
+
+### Added
+
+- Protection of stubbed methods from being called within a db transaction (nepalez)
+
+  ```yaml
+  ---
+  - class: GoogleTranslateDiff
+  - chain: translate
+  - within_transaction: false
+  - arguments:
+      - Color
+      - :from: en
+        :to:   de
+  - actions:
+      - return: Farbe
+  ```
+  
+  This method will raise an exception if the method is executed in a transaction:
+  
+  ```ruby
+  GoogleTranslateDiff.translate "Color", from: "en", to: "de"
+  # => "Farbe"  
+
+  # but not within a transaction
+  ActiveRecord::Base.transaction do
+    GoogleTranslateDiff.translate "Color", from: "en", to: "de"
+    # => raise #<Isolator::UnsafeOperationError ...>
+  end
+  ```
+
+  We use the [isolator][isolator] gem under the hood
+
 ## [0.0.7] - [2019-07-01]
 
 ### Added

README.md

@@ -131,6 +131,7 @@ For message chains:
 - `class` for stubbed class
 - `chain` for messages chain
 - `arguments` (optional) for specific arguments
+- `within_transaction` (default to `true`) if the method can be called within a database transaction
 - `actions` for an array of actions for consecutive invocations of the chain
 
 For constants:
@@ -161,6 +162,7 @@ Every action either `return` some value, or `raise` some exception
 - class: Notifier
   chain:
     - create
+  within_transaction: false
   arguments:
     - :profileDeleted
     - <%= profile_id %>

fixturama.gemspec

@@ -16,6 +16,7 @@ Gem::Specification.new do |gem|
   gem.add_runtime_dependency "factory_bot", "~> 4.0"
   gem.add_runtime_dependency "rspec", "~> 3.0"
   gem.add_runtime_dependency "hashie", "~> 3.6"
+  gem.add_runtime_dependency "isolator", "~> 0.6.1"
 
   gem.add_development_dependency "rake", "~> 10"
   gem.add_development_dependency "rspec-its", "~> 1.2"

lib/fixturama/stubs/chain.rb

@@ -24,11 +24,11 @@ def to_s
     # @option (see Fixturama::Stubs::Arguments#add_action)
     # @return [self]
     #
-    def update!(actions:, arguments: nil, **)
+    def update!(actions:, arguments: nil, within_transaction: true, **)
       Utils.array(arguments).tap do |args|
         stub = find_by(args)
         unless stub
-          stub = Stubs::Chain::Arguments.new(self, args)
+          stub = Stubs::Chain::Arguments.new(self, within_transaction, args)
           stubs << stub
         end
         stub.add!(*actions)

lib/fixturama/stubs/chain/arguments.rb

@@ -3,7 +3,7 @@ module Fixturama
   # Collection of arguments for a stub with a list of actions to be called
   #
   class Stubs::Chain::Arguments
-    attr_reader :chain, :arguments
+    attr_reader :chain, :arguments, :within_transaction
 
     #
     # Register new action for these set of arguments
@@ -54,7 +54,11 @@ def reset!
     # @raise  [StandardError]
     #
     def call_next!
-      list.fetch(counter) { list.last }.call.tap { @counter += 1 }
+      action = list.fetch(counter) { list.last }
+      isolate! unless within_transaction
+      action.call
+    ensure
+      @counter += 1
     end
 
     #
@@ -70,8 +74,9 @@ def to_s
 
     # @param [Fixturama::Stubs::Chain] chain Back reference
     # @param [Array<Object>] list Definition of arguments
-    def initialize(chain, list)
-      @chain     = chain
+    def initialize(chain, within_transaction, list)
+      @chain = chain
+      @within_transaction = within_transaction || (require("isolator") || false)
       @arguments = Utils.array(list)
     end
 
@@ -82,5 +87,13 @@ def counter
     def list
       @list ||= []
     end
+
+    def isolate!
+      return unless ::Isolator.within_transaction?
+
+      raise ::Isolator::UnsafeOperationError, <<~MESSAGE
+        You're trying to call #{self} inside db transaction
+      MESSAGE
+    end
   end
 end

spec/fixturama/stub_fixture/_spec.rb

@@ -34,6 +34,28 @@ def pay(_)
       end
     end
 
+    context "when called within a transaction" do
+      before do
+        allow(Isolator).to receive(:within_transaction?).and_return(true)
+      end
+
+      context "without the :within_transaction option" do
+        let(:arguments) { [2] }
+
+        it "raises an exception" do
+          expect { subject }.not_to raise_error
+        end
+      end
+
+      context "when the option :within_transaction was set to false" do
+        let(:arguments) { [1] }
+
+        it "raises an exception" do
+          expect { subject }.to raise_error(Isolator::UnsafeOperationError)
+        end
+      end
+    end
+
     context "with several actions" do
       let(:arguments) { [2] * 4 }
 

spec/fixturama/stub_fixture/stub.yml

@@ -19,6 +19,7 @@
   chain:
     - new
     - pay
+  within_transaction: false
   arguments:
     - 1
   actions: