Add tests for exotic rescued error capturing

The idiomatic way to capture exceptions is to assign to a local variable

    rescue => local_variable

However, other kinds of LVALUEs also work:

    rescue => $global_variable
    rescue => @@class_variable
    rescue => @instance_variable
    rescue => Constant
    rescue => receiver&.setter_method
    rescue => receiver.setter_method
    rescue => receiver[:key]

Author: sambostock

language/fixtures/rescue.rb

@@ -1,4 +1,104 @@
 module RescueSpecs
+  class ClassVariableCaptor
+    def capture(msg)
+      raise msg
+    rescue => @@captured_error
+      :caught
+    end
+
+    def captured_error
+      @@captured_error
+    end
+  end
+
+  class ConstantCaptor
+    # Using lambda gets around the dynamic constant assignment warning
+    CAPTURE = -> msg {
+      begin
+        raise msg
+      rescue => CapturedError
+        :caught
+      end
+    }
+
+    def capture(msg)
+      CAPTURE.call(msg)
+    end
+
+    def captured_error
+      CapturedError
+    end
+  end
+
+  class GlobalVariableCaptor
+    def capture(msg)
+      raise msg
+    rescue => $captured_error
+      :caught
+    end
+
+    def captured_error
+      $captured_error
+    end
+  end
+
+  class InstanceVariableCaptor
+    attr_reader :captured_error
+
+    def capture(msg)
+      raise msg
+    rescue => @captured_error
+      :caught
+    end
+  end
+
+  class LocalVariableCaptor
+    attr_reader :captured_error
+
+    def capture(msg)
+      raise msg
+    rescue => captured_error
+      @captured_error = captured_error
+      :caught
+    end
+  end
+
+  class SafeNavigationSetterCaptor
+    attr_accessor :captured_error
+
+    def capture(msg)
+      raise msg
+    rescue => self&.captured_error
+      :caught
+    end
+  end
+
+  class SetterCaptor
+    attr_accessor :captured_error
+
+    def capture(msg)
+      raise msg
+    rescue => self.captured_error
+      :caught
+    end
+  end
+
+  class SquareBracketsCaptor
+    def capture(msg)
+      raise msg
+    rescue => self[:error]
+      :caught
+    end
+
+    def []=(key, value)
+      (@hash ||= {})[key] = value
+    end
+
+    def captured_error
+      @hash[:error]
+    end
+  end
+
   def self.begin_else(raise_exception)
     begin
       ScratchPad << :one

language/rescue_spec.rb

@@ -23,11 +23,22 @@ class ArbitraryException < StandardError
     end.should == :caught
   end
 
-  it "can capture the raised exception in a local variable" do
-    begin
-      raise SpecificExampleException, "some text"
-    rescue SpecificExampleException => e
-      e.message.should == "some text"
+  {
+    # Standard use case
+    'can capture the raised exception in a local variable'                    => RescueSpecs::LocalVariableCaptor,
+    # Exotic use cases
+    'can capture the raised exception in a class variable'                    => RescueSpecs::ClassVariableCaptor,
+    'can capture the raised exception in a constant'                          => RescueSpecs::ConstantCaptor,
+    'can capture the raised exception in a global variable'                   => RescueSpecs::GlobalVariableCaptor,
+    'can capture the raised exception in an instance variable'                => RescueSpecs::InstanceVariableCaptor,
+    'can capture the raised exception using a safely navigated setter method' => RescueSpecs::SafeNavigationSetterCaptor,
+    'can capture the raised exception using a setter method'                  => RescueSpecs::SetterCaptor,
+    'can capture the raised exception using a square brackets setter'         => RescueSpecs::SquareBracketsCaptor,
+  }.each do |description, klass|
+    it description do
+      captor = klass.new
+      captor.capture('some text').should == :caught # Ensure rescue body still runs
+      captor.captured_error.message.should == 'some text'
     end
   end