Add new RSpec/FileFixture cop

`RSpec` provides the convenience method ```ruby file_fixture('path/some_file.csv') ``` which (by default) is equivalent to ```ruby Rails.root.join('spec/fixtures/files/path/some_file.csv') ``` We add a cop which detects and autocorrects verbose `Rails.root` constructions and works best in combination with [`Rails/RootPathnameMethods`](rubocop/rubocop-rails#587).
leoarnold · Nov 21, 2021 · 1f21db6 · 1f21db6
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -651,3 +651,4 @@ Compatibility release so users can upgrade RuboCop to 0.51.0. No new features.
 [@dswij]: https://github.com/dswij
 [@francois-ferrandis]: https://github.com/francois-ferrandis
 [@r7kamura]: https://github.com/r7kamura
+[@leoarnold]: https://github.com/leoarnold
diff --git a/changelog/new_add_new_rspecfilefixture_cop.md b/changelog/new_add_new_rspecfilefixture_cop.md
@@ -0,0 +1 @@
+* [#1214](https://github.com/rubocop/rubocop-rails/pull/1214): Add new `RSpec/FileFixture` cop. ([@leoarnold][])
diff --git a/config/default.yml b/config/default.yml
@@ -353,6 +353,12 @@ RSpec/ExpectOutput:
   VersionAdded: '1.10'
   StyleGuide: https://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/ExpectOutput
 
+RSpec/FileFixture:
+  Description: Favor the use of `file_fixture`.
+  Enabled: pending
+  VersionAdded: 2.7.0
+  StyleGuide: https://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/FileFixture
+
 RSpec/FilePath:
   Description: Checks that spec file paths are consistent and well-formed.
   Enabled: true

diff --git a/docs/modules/ROOT/pages/cops.adoc b/docs/modules/ROOT/pages/cops.adoc
@@ -32,6 +32,7 @@
 * xref:cops_rspec.adoc#rspecexpectchange[RSpec/ExpectChange]
 * xref:cops_rspec.adoc#rspecexpectinhook[RSpec/ExpectInHook]
 * xref:cops_rspec.adoc#rspecexpectoutput[RSpec/ExpectOutput]
+* xref:cops_rspec.adoc#rspecfilefixture[RSpec/FileFixture]
 * xref:cops_rspec.adoc#rspecfilepath[RSpec/FilePath]
 * xref:cops_rspec.adoc#rspecfocus[RSpec/Focus]
 * xref:cops_rspec.adoc#rspechookargument[RSpec/HookArgument]

diff --git a/docs/modules/ROOT/pages/cops_rspec.adoc b/docs/modules/ROOT/pages/cops_rspec.adoc
@@ -1491,6 +1491,61 @@ expect { my_app.print_report }.to output('Hello World').to_stdout
 
 * https://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/ExpectOutput
 
+== RSpec/FileFixture
+
+|===
+| Enabled by default | Safe | Supports autocorrection | Version Added | Version Changed
+
+| Pending
+| Yes
+| Yes
+| 2.7.0
+| -
+|===
+
+Favor the use of `file_fixture`.
+
+`RSpec` provides the convenience method
+
+[source,ruby]
+----
+file_fixture('path/some_file.csv')
+----
+
+which (by default) is equivalent to
+
+[source,ruby]
+----
+Rails.root.join('spec/fixtures/files/path/some_file.csv')
+----
+
+=== Examples
+
+[source,ruby]
+----
+# bad
+"#{Rails.root}/spec/fixtures/path/some_file.csv"
+Rails.root.join('spec/fixtures/path/some_file.csv')
+Rails.root.join('spec', 'fixtures', 'path', 'some_file.csv')
+
+"#{Rails.root}/spec/fixtures/files/some_file.csv"
+Rails.root.join('spec/fixtures/files/some_file.csv')
+Rails.root.join('spec', 'fixtures', 'files', 'some_file.csv')
+
+# good
+file_fixture('../path/some_file.csv').path
+file_fixture('../path/some_file.csv')
+file_fixture('../path/some_file.csv')
+
+file_fixture('some_file.csv').path
+file_fixture('some_file.csv')
+file_fixture('some_file.csv')
+----
+
+=== References
+
+* https://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/FileFixture
+
 == RSpec/FilePath
 
 |===

diff --git a/lib/rubocop/cop/rspec/file_fixture.rb b/lib/rubocop/cop/rspec/file_fixture.rb
@@ -0,0 +1,107 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module RSpec
+      # Favor the use of `file_fixture`.
+      #
+      # `RSpec` provides the convenience method
+      #
+      # [source,ruby]
+      # ----
+      # file_fixture('path/some_file.csv')
+      # ----
+      #
+      # which (by default) is equivalent to
+      #
+      # [source,ruby]
+      # ----
+      # Rails.root.join('spec/fixtures/files/path/some_file.csv')
+      # ----
+      #
+      # @example
+      #   # bad
+      #   "#{Rails.root}/spec/fixtures/path/some_file.csv"
+      #   Rails.root.join('spec/fixtures/path/some_file.csv')
+      #   Rails.root.join('spec', 'fixtures', 'path', 'some_file.csv')
+      #
+      #   "#{Rails.root}/spec/fixtures/files/some_file.csv"
+      #   Rails.root.join('spec/fixtures/files/some_file.csv')
+      #   Rails.root.join('spec', 'fixtures', 'files', 'some_file.csv')
+      #
+      #   # good
+      #   file_fixture('../path/some_file.csv').path
+      #   file_fixture('../path/some_file.csv')
+      #   file_fixture('../path/some_file.csv')
+      #
+      #   file_fixture('some_file.csv').path
+      #   file_fixture('some_file.csv')
+      #   file_fixture('some_file.csv')
+      #
+      class FileFixture < Base
+        extend AutoCorrector
+
+        MSG = 'Use `file_fixture`.'
+
+        RESTRICT_ON_SEND = %i[join root].freeze
+
+        DEFAULT_FILE_FIXTURE_PATTERN = %r{^spec/fixtures/files/}.freeze
+        DEFAULT_FIXTURE_PATTERN = %r{^spec/fixtures/}.freeze
+
+        # @!method file_io?(node)
+        def_node_matcher :file_io?, <<~PATTERN
+          (send
+            (const {nil? cbase} :File) {:binread :binwrite :open :read :write} $...)
+        PATTERN
+
+        # @!method rails_root_join(node)
+        def_node_matcher :rails_root_join, <<~PATTERN
+          (send
+            (send
+              (const {nil? cbase} :Rails) :root) :join (str $_)+)
+        PATTERN
+
+        # @!method dstr_rails_root(node)
+        def_node_matcher :dstr_rails_root, <<~PATTERN
+          (dstr
+            (begin
+              (send
+                (const {nil? cbase} :Rails) :root))
+            (str $_))
+        PATTERN
+
+        def on_send(node)
+          return unless (crime_scene, strings, method = evidence(node))
+          return unless (new_path = new_path(strings))
+
+          add_offense(crime_scene) do |corrector|
+            replacement = "file_fixture('#{new_path}')"
+            replacement += ".#{method}" if method
+
+            corrector.replace(crime_scene, replacement)
+          end
+        end
+
+        private
+
+        def evidence(node)
+          if !file_io?(node.parent) && (string = rails_root_join(node))
+            [node, string, nil]
+          elsif (string = dstr_rails_root(node.parent.parent))
+            [node.parent.parent, string.gsub(%r{^/}, ''), :path]
+          end
+        end
+
+        def new_path(strings)
+          path = File.join(strings)
+
+          if DEFAULT_FILE_FIXTURE_PATTERN.match?(path)
+            path.gsub(DEFAULT_FILE_FIXTURE_PATTERN, '')
+          elsif DEFAULT_FIXTURE_PATTERN.match?(path)
+            path.gsub(DEFAULT_FIXTURE_PATTERN, '../')
+          end
+        end
+      end
+    end
+  end
+end
diff --git a/lib/rubocop/cop/rspec_cops.rb b/lib/rubocop/cop/rspec_cops.rb
@@ -45,6 +45,7 @@
 require_relative 'rspec/expect_change'
 require_relative 'rspec/expect_in_hook'
 require_relative 'rspec/expect_output'
+require_relative 'rspec/file_fixture'
 require_relative 'rspec/file_path'
 require_relative 'rspec/focus'
 require_relative 'rspec/hook_argument'

diff --git a/spec/rubocop/cop/rspec/file_fixture_spec.rb b/spec/rubocop/cop/rspec/file_fixture_spec.rb
@@ -0,0 +1,145 @@
+# frozen_string_literal: true
+
+RSpec.describe RuboCop::Cop::RSpec::FileFixture, :config do
+  it 'registers an offense when using ' \
+     '`"\#{Rails.root}/spec/fixtures/files/some_file.csv"`' do
+    expect_offense(<<~RUBY)
+      "\#{Rails.root}/spec/fixtures/files/some_file.csv"
+      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Use `file_fixture`.
+    RUBY
+
+    expect_correction(<<~RUBY)
+      file_fixture('some_file.csv').path
+    RUBY
+  end
+
+  it 'registers an offense when using ' \
+     '`"\#{::Rails.root}/spec/fixtures/path/some_file.csv"`' do
+    expect_offense(<<~RUBY)
+      "\#{::Rails.root}/spec/fixtures/path/some_file.csv"
+      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Use `file_fixture`.
+    RUBY
+
+    expect_correction(<<~RUBY)
+      file_fixture('../path/some_file.csv').path
+    RUBY
+  end
+
+  it 'registers an offense when using ' \
+     "`Rails.root.join('spec/fixtures/files/some_file.csv')`" do
+    expect_offense(<<~RUBY)
+      Rails.root.join('spec/fixtures/files/some_file.csv')
+      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Use `file_fixture`.
+    RUBY
+
+    expect_correction(<<~RUBY)
+      file_fixture('some_file.csv')
+    RUBY
+  end
+
+  it 'registers an offense when using ' \
+     "`::Rails.root.join('spec/fixtures/path/some_file.csv')`" do
+    expect_offense(<<~RUBY)
+      ::Rails.root.join('spec/fixtures/path/some_file.csv')
+      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Use `file_fixture`.
+    RUBY
+
+    expect_correction(<<~RUBY)
+      file_fixture('../path/some_file.csv')
+    RUBY
+  end
+
+  it 'registers an offense when using ' \
+     "`Rails.root.join('spec', 'fixtures/path/some_file.csv')`" do
+    expect_offense(<<~RUBY)
+      Rails.root.join('spec', 'fixtures/path/some_file.csv')
+      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Use `file_fixture`.
+    RUBY
+
+    expect_correction(<<~RUBY)
+      file_fixture('../path/some_file.csv')
+    RUBY
+  end
+
+  it 'registers an offense when using ' \
+     "`Rails.root.join('spec/fixtures', 'path/some_file.csv')`" do
+    expect_offense(<<~RUBY)
+      Rails.root.join('spec/fixtures', 'path/some_file.csv')
+      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Use `file_fixture`.
+    RUBY
+
+    expect_correction(<<~RUBY)
+      file_fixture('../path/some_file.csv')
+    RUBY
+  end
+
+  it 'registers an offense when using ' \
+     "`Rails.root.join('spec/fixtures/path', 'some_file.csv')`" do
+    expect_offense(<<~RUBY)
+      Rails.root.join('spec/fixtures/path', 'some_file.csv')
+      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Use `file_fixture`.
+    RUBY
+
+    expect_correction(<<~RUBY)
+      file_fixture('../path/some_file.csv')
+    RUBY
+  end
+
+  it 'registers an offense when using ' \
+     "`Rails.root.join('spec', 'fixtures', 'path/some_file.csv')`" do
+    expect_offense(<<~RUBY)
+      Rails.root.join('spec', 'fixtures', 'path/some_file.csv')
+      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Use `file_fixture`.
+    RUBY
+
+    expect_correction(<<~RUBY)
+      file_fixture('../path/some_file.csv')
+    RUBY
+  end
+
+  it 'registers an offense when using ' \
+     "`Rails.root.join('spec', 'fixtures/path', 'some_file.csv')`" do
+    expect_offense(<<~RUBY)
+      Rails.root.join('spec', 'fixtures/path', 'some_file.csv')
+      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Use `file_fixture`.
+    RUBY
+
+    expect_correction(<<~RUBY)
+      file_fixture('../path/some_file.csv')
+    RUBY
+  end
+
+  it 'registers an offense when using ' \
+     "`Rails.root.join('spec/fixtures', 'path', 'some_file.csv')`" do
+    expect_offense(<<~RUBY)
+      Rails.root.join('spec/fixtures', 'path', 'some_file.csv')
+      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Use `file_fixture`.
+    RUBY
+
+    expect_correction(<<~RUBY)
+      file_fixture('../path/some_file.csv')
+    RUBY
+  end
+
+  it 'registers an offense when using ' \
+     "`Rails.root.join('spec', 'fixtures', 'path', 'some_file.csv')`" do
+    expect_offense(<<~RUBY)
+      Rails.root.join('spec', 'fixtures', 'path', 'some_file.csv')
+      ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ Use `file_fixture`.
+    RUBY
+
+    expect_correction(<<~RUBY)
+      file_fixture('../path/some_file.csv')
+    RUBY
+  end
+
+  %i[binread binwrite open read write].each do |method|
+    # This is handled by `Rails/RootPathnameMethods`
+    it 'does not register an offense when using ' \
+     "`File.#{method}(Rails.root.join(...))`" do
+      expect_no_offenses(<<~RUBY)
+        File.#{method}(Rails.root.join('spec', 'fixtures', 'path', 'some_file.csv'))
+      RUBY
+    end
+  end
+end