spec/rubocop/cop/performance/readlines_each_spec.rb


1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82

# frozen_string_literal: true

require 'fast_spec_helper'
require_relative '../../../../rubocop/cop/performance/readlines_each'

RSpec.describe RuboCop::Cop::Performance::ReadlinesEach do
  subject(:cop) { described_class.new }

  let(:message) { 'Avoid `IO.readlines.each`, since it reads contents into memory in full. Use `IO.each_line` or `IO.each` instead.' }

  shared_examples_for(:class_read) do |klass|
    context "and it is called as a class method on #{klass}" do
      it 'flags it as an offense' do
        leading_readline = "#{klass}.readlines(file_path)."
        padding = " " * leading_readline.length
        node = "#{leading_readline}each { |line| puts line }"

        expect_offense(<<~CODE, node: node)
          %{node}
          #{padding}^^^^ Avoid `IO.readlines.each`, since it reads contents into memory in full. [...]
        CODE
      end
    end

    context 'when just using readlines without each' do
      it 'does not flag it as an offense' do
        expect_no_offenses "contents = #{klass}.readlines(file_path)"
      end
    end
  end

  context 'when reading all lines using IO.readlines.each' do
    %w(IO File).each do |klass|
      it_behaves_like(:class_read, klass)
    end

    context 'and it is called as an instance method on a return value' do
      it 'flags it as an offense' do
        expect_offense <<~SOURCE
          get_file.readlines.each { |line| puts line }
                             ^^^^ #{message}
        SOURCE
      end
    end

    context 'and it is called as an instance method on an assigned variable' do
      it 'flags it as an offense' do
        expect_offense <<~SOURCE
          file = File.new(path)
          file.readlines.each { |line| puts line }
                         ^^^^ #{message}
        SOURCE
      end
    end

    context 'and it is called as an instance method on a new object' do
      it 'flags it as an offense' do
        expect_offense <<~SOURCE
          File.new(path).readlines.each { |line| puts line }
                                   ^^^^ #{message}
        SOURCE
      end
    end

    it 'autocorrects `readlines.each` to `each_line`' do
      expect_offense(<<~CODE)
        obj.readlines.each { |line| line }
                      ^^^^ Avoid `IO.readlines.each`, since it reads contents into memory in full. [...]
      CODE

      expect_correction(<<~CODE)
        obj.each_line { |line| line }
      CODE
    end
  end

  context 'when just using readlines without each' do
    it 'does not flag it as an offense' do
      expect_no_offenses 'contents = my_file.readlines'
    end
  end
end