WIP - Automatically fail context on exception

interactor.gemspec

@@ -1,17 +1,17 @@
 require "English"
 
 Gem::Specification.new do |spec|
-  spec.name    = "interactor"
+  spec.name = "interactor"
   spec.version = "3.1.1"
 
-  spec.author      = "Collective Idea"
-  spec.email       = "[email protected]"
+  spec.author = "Collective Idea"
+  spec.email = "[email protected]"
   spec.description = "Interactor provides a common interface for performing complex user interactions."
-  spec.summary     = "Simple interactor implementation"
-  spec.homepage    = "https://github.com/collectiveidea/interactor"
-  spec.license     = "MIT"
+  spec.summary = "Simple interactor implementation"
+  spec.homepage = "https://github.com/collectiveidea/interactor"
+  spec.license = "MIT"
 
-  spec.files      = `git ls-files`.split($INPUT_RECORD_SEPARATOR)
+  spec.files = `git ls-files`.split($INPUT_RECORD_SEPARATOR)
   spec.test_files = spec.files.grep(/^spec/)
 
   spec.add_development_dependency "bundler"

lib/interactor.rb

@@ -22,13 +22,72 @@ def self.included(base)
       extend ClassMethods
       include Hooks
 
+      # Internal: Expose instance variables of Interactor instance metaclass
+      # for reading.
+      class << self
+        attr_reader :exception_classes
+        attr_reader :exception_handlers
+      end
       # Public: Gets the Interactor::Context of the Interactor instance.
       attr_reader :context
     end
   end
 
   # Internal: Interactor class methods.
   module ClassMethods
+    # Public: Specify exception classes that should result in failing context
+    # and provide a custom logic on rescued exception before failing. Failing
+    # the context is raising Interactor::Failure, this exception is silently
+    # swallowed by the interactor. Note that any code after failing the context
+    # will not be evaluated.
+    #
+    # Examples
+    #   class MyInteractor
+    #     include Interactor
+    #
+    #     fail_on_exception StandardErro
+    #     fail_on_exception NameError, NoMethodError
+    #
+    #     exception_handler = ->(e) { ErrorLogger.log(e) }
+    #
+    #     fail_on_exception MyBespokeError, exception_handler: exception_handler
+    #
+    #     def call
+    #       exception_raising_logic
+    #     end
+    #   end
+    #
+    #   MyInteractor.call
+    #   # => #<Interactor::Context error=#<NameError: undefined local variable
+    #   or method `method_raising_exception' for
+    #   #<MyInteractor:0x0000000003d17330> Did you mean?  method_missing>>
+    #
+    #   MyInteractor.call.success?
+    #   # => false
+    #
+    #   Returned context holds the rescued exception object
+    #
+    #   MyInteractor.call.error.class.name
+    #   # => "NameError"
+    #
+    #   Method accepts object representing exception classes of any type that
+    #   will respond to #to_s and return string, as an argument to
+    #   Kernel.const_get will result in previously initialized constant.
+    #   e.g. constant, symbol, string...
+
+    def fail_on_exception(*exceptions_to_fail_on, exception_handler: ->(e) {})
+      exceptions_to_fail_on = exceptions_to_fail_on.each do |it|
+        Kernel.const_get(it.to_s)
+      end
+      @exception_classes = Array(exception_classes) | exceptions_to_fail_on
+      return unless exception_handler
+      exceptions_to_fail_on.each do |exception_class|
+        @exception_handlers = Hash(exception_handlers).update(
+          exception_class.name.to_sym => exception_handler
+        )
+      end
+    end
+
     # Public: Invoke an Interactor. This is the primary public API method to an
     # interactor.
     #
@@ -140,8 +199,13 @@ def run
   # Raises Interactor::Failure if the context is failed.
   def run!
     with_hooks do
-      call
-      context.called!(self)
+      begin
+        call
+        context.called!(self)
+      rescue *self.class.exception_classes => e
+        self.class.exception_handlers[e.class.name.to_sym]&.call(e)
+        context.fail!(error: e)
+      end
     end
   rescue
     context.rollback!