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# frozen_string_literal: true
require 'set'
module RuboCop
module Cop
module RSpec
# Checks for stubbed test subjects.
#
# Checks nested subject stubs for innermost subject definition
# when subject is also defined in parent example groups.
#
# @see https://robots.thoughtbot.com/don-t-stub-the-system-under-test
# @see https://penelope.zone/2015/12/27/introducing-rspec-smells-and-where-to-find-them.html#smell-1-stubjec
# @see https://github.com/rubocop-hq/rspec-style-guide#dont-stub-subject
#
# @example
# # bad
# describe Article do
# subject(:article) { Article.new }
#
# it 'indicates that the author is unknown' do
# allow(article).to receive(:author).and_return(nil)
# expect(article.description).to include('by an unknown author')
# end
# end
#
# # bad
# describe Article do
# subject(:foo) { Article.new }
#
# context 'nested subject' do
# subject(:article) { Article.new }
#
# it 'indicates that the author is unknown' do
# allow(article).to receive(:author).and_return(nil)
# expect(article.description).to include('by an unknown author')
# end
# end
# end
#
# # good
# describe Article do
# subject(:article) { Article.new(author: nil) }
#
# it 'indicates that the author is unknown' do
# expect(article.description).to include('by an unknown author')
# end
# end
#
class SubjectStub < Base
include TopLevelGroup
MSG = 'Do not stub methods of the object under test.'
# @!method subject?(node)
# Find a named or unnamed subject definition
#
# @example anonymous subject
# subject?(parse('subject { foo }').ast) do |name|
# name # => :subject
# end
#
# @example named subject
# subject?(parse('subject(:thing) { foo }').ast) do |name|
# name # => :thing
# end
#
# @param node [RuboCop::AST::Node]
#
# @yield [Symbol] subject name
def_node_matcher :subject?, <<-PATTERN
(block
(send nil?
{ #Subjects.all (sym $_) | $#Subjects.all }
) args ...)
PATTERN
# @!method let?(node)
# Find a memoized helper
def_node_matcher :let?, <<-PATTERN
(block
(send nil? :let (sym $_)
) args ...)
PATTERN
# @!method message_expectation?(node, method_name)
# Match `allow` and `expect(...).to receive`
#
# @example source that matches
# allow(foo).to receive(:bar)
# allow(foo).to receive(:bar).with(1)
# allow(foo).to receive(:bar).with(1).and_return(2)
# expect(foo).to receive(:bar)
# expect(foo).to receive(:bar).with(1)
# expect(foo).to receive(:bar).with(1).and_return(2)
#
def_node_matcher :message_expectation?, <<-PATTERN
(send
{
(send nil? { :expect :allow } (send nil? %))
(send nil? :is_expected)
}
#Runners.all
#message_expectation_matcher?
)
PATTERN
# @!method message_expectation_matcher?(node)
def_node_search :message_expectation_matcher?, <<-PATTERN
(send nil? {
:receive :receive_messages :receive_message_chain :have_received
} ...)
PATTERN
def on_top_level_group(node)
@explicit_subjects = find_all_explicit(node, &method(:subject?))
@subject_overrides = find_all_explicit(node, &method(:let?))
find_subject_expectations(node) do |stub|
add_offense(stub)
end
end
private
def find_all_explicit(node)
node.each_descendant(:block).with_object({}) do |child, h|
name = yield(child)
next unless name
outer_example_group = child.each_ancestor(:block).find do |a|
example_group?(a)
end
h[outer_example_group] ||= []
h[outer_example_group] << name
end
end
def find_subject_expectations(node, subject_names = [], &block)
subject_names = [*subject_names, *@explicit_subjects[node]]
subject_names -= @subject_overrides[node] if @subject_overrides[node]
names = Set[*subject_names, :subject]
expectation_detected = message_expectation?(node, names)
return yield(node) if expectation_detected
node.each_child_node(:send, :def, :block, :begin) do |child|
find_subject_expectations(child, subject_names, &block)
end
end
end
end
end
end
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