From 8dd097a91530e4b047c4b391f21047c7d29d310d Mon Sep 17 00:00:00 2001
From: Sean McGivern <sean@gitlab.com>
Date: Tue, 28 Feb 2017 10:41:59 +0000
Subject: Add RuboCop cop for custom error classes
From the Ruby style guide:
# bad
class FooError < StandardError
end
# okish
class FooError < StandardError; end
# good
FooError = Class.new(StandardError)
This cop does that, but only for error classes (classes where the
superclass ends in 'Error'). We have empty controllers and models, which
are perfectly valid empty classes.
---
rubocop/cop/custom_error_class.rb | 64 +++++++++++++++++++++++++++++++++++++++
1 file changed, 64 insertions(+)
create mode 100644 rubocop/cop/custom_error_class.rb
(limited to 'rubocop')
diff --git a/rubocop/cop/custom_error_class.rb b/rubocop/cop/custom_error_class.rb
new file mode 100644
index 00000000000..38d93acfe88
--- /dev/null
+++ b/rubocop/cop/custom_error_class.rb
@@ -0,0 +1,64 @@
+module RuboCop
+ module Cop
+ # This cop makes sure that custom error classes, when empty, are declared
+ # with Class.new.
+ #
+ # @example
+ # # bad
+ # class FooError < StandardError
+ # end
+ #
+ # # okish
+ # class FooError < StandardError; end
+ #
+ # # good
+ # FooError = Class.new(StandardError)
+ class CustomErrorClass < RuboCop::Cop::Cop
+ MSG = 'Use `Class.new(SuperClass)` to define an empty custom error class.'.freeze
+
+ def on_class(node)
+ _klass, parent, body = node.children
+
+ return if body
+
+ parent_klass = class_name_from_node(parent)
+
+ return unless parent_klass && parent_klass.to_s.end_with?('Error')
+
+ add_offense(node, :expression)
+ end
+
+ def autocorrect(node)
+ klass, parent, _body = node.children
+ replacement = "#{class_name_from_node(klass)} = Class.new(#{class_name_from_node(parent)})"
+
+ lambda do |corrector|
+ corrector.replace(node.source_range, replacement)
+ end
+ end
+
+ private
+
+ # The nested constant `Foo::Bar::Baz` looks like:
+ #
+ # s(:const,
+ # s(:const,
+ # s(:const, nil, :Foo), :Bar), :Baz)
+ #
+ # So recurse through that to get the name as written in the source.
+ #
+ def class_name_from_node(node, suffix = nil)
+ return unless node&.type == :const
+
+ name = node.children[1].to_s
+ name = "#{name}::#{suffix}" if suffix
+
+ if node.children[0]
+ class_name_from_node(node.children[0], name)
+ else
+ name
+ end
+ end
+ end
+ end
+end
--
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