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authorSean McGivern <sean@gitlab.com>2017-02-28 10:41:59 +0000
committerSean McGivern <sean@gitlab.com>2017-03-01 10:53:10 +0000
commit8dd097a91530e4b047c4b391f21047c7d29d310d (patch)
treee05f69a73b248d88c6dd61c61808f84d6b82b9af
parent6b4d490782a7b0c2a4a7f7eb6ed5ef2c25fc1c4d (diff)
downloadgitlab-ce-8dd097a91530e4b047c4b391f21047c7d29d310d.tar.gz
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.
-rw-r--r--rubocop/cop/custom_error_class.rb64
-rw-r--r--spec/rubocop/cop/custom_error_class_spec.rb111
2 files changed, 175 insertions, 0 deletions
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
diff --git a/spec/rubocop/cop/custom_error_class_spec.rb b/spec/rubocop/cop/custom_error_class_spec.rb
new file mode 100644
index 00000000000..381d7871a40
--- /dev/null
+++ b/spec/rubocop/cop/custom_error_class_spec.rb
@@ -0,0 +1,111 @@
+require 'spec_helper'
+
+require 'rubocop'
+require 'rubocop/rspec/support'
+
+require_relative '../../../rubocop/cop/custom_error_class'
+
+describe RuboCop::Cop::CustomErrorClass do
+ include CopHelper
+
+ subject(:cop) { described_class.new }
+
+ context 'when a class has a body' do
+ it 'does nothing' do
+ inspect_source(cop, 'class CustomError < StandardError; def foo; end; end')
+
+ expect(cop.offenses).to be_empty
+ end
+ end
+
+ context 'when a class has no explicit superclass' do
+ it 'does nothing' do
+ inspect_source(cop, 'class CustomError; end')
+
+ expect(cop.offenses).to be_empty
+ end
+ end
+
+ context 'when a class has a superclass that does not end in Error' do
+ it 'does nothing' do
+ inspect_source(cop, 'class CustomError < BasicObject; end')
+
+ expect(cop.offenses).to be_empty
+ end
+ end
+
+ context 'when a class is empty and inherits from a class ending in Error' do
+ context 'when the class is on a single line' do
+ let(:source) do
+ <<-SOURCE
+ module Foo
+ class CustomError < Bar::Baz::BaseError; end
+ end
+ SOURCE
+ end
+
+ let(:expected) do
+ <<-EXPECTED
+ module Foo
+ CustomError = Class.new(Bar::Baz::BaseError)
+ end
+ EXPECTED
+ end
+
+ it 'registers an offense' do
+ expected_highlights = source.split("\n")[1].strip
+
+ inspect_source(cop, source)
+
+ aggregate_failures do
+ expect(cop.offenses.size).to eq(1)
+ expect(cop.offenses.map(&:line)).to eq([2])
+ expect(cop.highlights).to contain_exactly(expected_highlights)
+ end
+ end
+
+ it 'autocorrects to the right version' do
+ autocorrected = autocorrect_source(cop, source, 'foo/custom_error.rb')
+
+ expect(autocorrected).to eq(expected)
+ end
+ end
+
+ context 'when the class is on multiple lines' do
+ let(:source) do
+ <<-SOURCE
+ module Foo
+ class CustomError < Bar::Baz::BaseError
+ end
+ end
+ SOURCE
+ end
+
+ let(:expected) do
+ <<-EXPECTED
+ module Foo
+ CustomError = Class.new(Bar::Baz::BaseError)
+ end
+ EXPECTED
+ end
+
+ it 'registers an offense' do
+ expected_highlights = source.split("\n")[1..2].join("\n").strip
+
+ inspect_source(cop, source)
+
+ aggregate_failures do
+ expect(cop.offenses.size).to eq(1)
+ expect(cop.offenses.map(&:line)).to eq([2])
+ expect(cop.highlights).to contain_exactly(expected_highlights)
+ end
+ end
+
+ it 'autocorrects to the right version' do
+ autocorrected = autocorrect_source(cop, source, 'foo/custom_error.rb')
+
+ expect(autocorrected).to eq(expected)
+ end
+ end
+ end
+end