Add RSpec/StringAsInstanceDoubleConstant

Addresses #1136

Adds a cop which can autocorrect from String declarations for instance_double to Class declarations. Symbol declarations are not affected.

.rubocop.yml

@@ -101,34 +101,34 @@ RSpec:
       - expect_no_offenses
       - expect_offense
 
+RSpec/DescribeClass:
+  Exclude:
+    - spec/project/**/*.rb
+
 RSpec/ExampleLength:
   CountAsOne:
     - heredoc
   Max: 11
 
-RSpec/DescribeClass:
-  Exclude:
-    - spec/project/**/*.rb
-
 RSpec/MultipleExpectations:
   Max: 2
 
+RSpec/SpecFilePathFormat:
+  Exclude:
+    - spec/rubocop/cop/rspec/mixin/**/*.rb
+
 # `expect_offense` does not use Kernel#format or String#%
 Style/FormatStringToken:
   Exclude:
     - spec/rubocop/**/*.rb
 
-Style/RequireOrder:
-  Enabled: true
-
-RSpec/SpecFilePathFormat:
-  Exclude:
-    - spec/rubocop/cop/rspec/mixin/**/*.rb
-
 Style/NumberedParameters:
   Enabled: true
   EnforcedStyle: disallow
 
+Style/RequireOrder:
+  Enabled: true
+
 # Enable RuboCop's pending cops up to v1.63
 
 Gemspec/DeprecatedAttributeAssignment: {Enabled: true}
@@ -253,4 +253,5 @@ Style/YAMLFileRead: {Enabled: true}
 
 # Enable our own pending cops.
 #
-# No pending cops yet.
+RSpec/StringAsInstanceDoubleConstant:
+  Enabled: true

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## Master (Unreleased)
 
+- Add `RSpec/StringAsInstanceDoubleConstant` to check for and correct strings used as instance_doubles. ([@corsonknowles])
+- Fix false-positive for `RSpec/UnspecifiedException` when a method is literally named `raise_exception`. ([@aarestad])
+- Fix false-positive for `RSpec/UnspecifiedException` when `not_to raise_error` is used within a block. ([@aarestad], [@G-Rath])
+
 ## 3.0.5 (2024-09-07)
 
 - Fix false-negative and error for `RSpec/MetadataStyle` when non-literal args are used in metadata in `EnforceStyle: hash`. ([@cbliard])
@@ -899,6 +903,7 @@ Compatibility release so users can upgrade RuboCop to 0.51.0. No new features.
 
 <!-- Contributors (alphabetically) -->
 
+[@aarestad]: https://github.com/aarestad
 [@abrom]: https://github.com/abrom
 [@ahukkanen]: https://github.com/ahukkanen
 [@akiomik]: https://github.com/akiomik
@@ -920,6 +925,7 @@ Compatibility release so users can upgrade RuboCop to 0.51.0. No new features.
 [@cfabianski]: https://github.com/cfabianski
 [@clupprich]: https://github.com/clupprich
 [@composerinteralia]: https://github.com/composerinteralia
+[@corsonknowles]: https://github.com/corsonknowles
 [@corydiamand]: https://github.com/corydiamand
 [@darhazer]: https://github.com/Darhazer
 [@daveworth]: https://github.com/daveworth

config/default.yml

@@ -929,6 +929,13 @@ RSpec/SpecFilePathSuffix:
     - "**/spec/**/*"
   Reference: https://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/SpecFilePathSuffix
 
+RSpec/StringAsInstanceDoubleConstant:
+  Description: Do not use a string as `instance_double` constant.
+  Enabled: pending
+  Safe: false
+  VersionAdded: "<<next>>"
+  Reference: https://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/StringAsInstanceDoubleConstant
+
 RSpec/StubbedMock:
   Description: Checks that message expectations do not have a configured response.
   Enabled: true

docs/modules/ROOT/pages/cops.adoc

@@ -101,6 +101,7 @@
 * xref:cops_rspec.adoc#rspecsortmetadata[RSpec/SortMetadata]
 * xref:cops_rspec.adoc#rspecspecfilepathformat[RSpec/SpecFilePathFormat]
 * xref:cops_rspec.adoc#rspecspecfilepathsuffix[RSpec/SpecFilePathSuffix]
+* xref:cops_rspec.adoc#rspecstringasinstancedoubleconstant[RSpec/StringAsInstanceDoubleConstant]
 * xref:cops_rspec.adoc#rspecstubbedmock[RSpec/StubbedMock]
 * xref:cops_rspec.adoc#rspecsubjectdeclaration[RSpec/SubjectDeclaration]
 * xref:cops_rspec.adoc#rspecsubjectstub[RSpec/SubjectStub]

docs/modules/ROOT/pages/cops_rspec.adoc

@@ -5493,6 +5493,41 @@ spec/models/user.rb       # shared_examples_for 'foo'
 
 * https://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/SpecFilePathSuffix
 
+== RSpec/StringAsInstanceDoubleConstant
+
+|===
+| Enabled by default | Safe | Supports autocorrection | Version Added | Version Changed
+
+| Pending
+| No
+| Always (Unsafe)
+| <<next>>
+| -
+|===
+
+Do not use a string as `instance_double` constant.
+
+=== Safety
+
+This cop is unsafe because the correction requires loading the class.
+Loading before stubbing causes RSpec to only allow instance methods
+to be stubbed.
+
+=== Examples
+
+[source,ruby]
+----
+# bad
+instance_double('User', name: 'John')
+
+# good
+instance_double(User, name: 'John')
+----
+
+=== References
+
+* https://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/StringAsInstanceDoubleConstant
+
 == RSpec/StubbedMock
 
 |===

lib/rubocop/cop/rspec/change_by_zero.rb

@@ -104,12 +104,12 @@ def on_send(node)
         # rubocop:disable Metrics/MethodLength
         def register_offense(node, change_node)
           if compound_expectations?(node)
-            add_offense(node.source_range,
+            add_offense(node,
                         message: message_compound(change_node)) do |corrector|
               autocorrect_compound(corrector, node)
             end
           else
-            add_offense(node.source_range,
+            add_offense(node,
                         message: message(change_node)) do |corrector|
               autocorrect(corrector, node, change_node)
             end

lib/rubocop/cop/rspec/expect_actual.rb

@@ -69,7 +69,7 @@ def on_send(node) # rubocop:disable Metrics/MethodLength
           expect_literal(node) do |actual, send_node, matcher, expected|
             next if SKIPPED_MATCHERS.include?(matcher)
 
-            add_offense(actual.source_range) do |corrector|
+            add_offense(actual) do |corrector|
               next unless CORRECTABLE_MATCHERS.include?(matcher)
               next if literal?(expected)
 

lib/rubocop/cop/rspec/string_as_instance_double_constant.rb

@@ -0,0 +1,45 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module RSpec
+      # Do not use a string as `instance_double` constant.
+      #
+      # @safety
+      #   This cop is unsafe because the correction requires loading the class.
+      #   Loading before stubbing causes RSpec to only allow instance methods
+      #   to be stubbed.
+      #
+      # @example
+      #   # bad
+      #   instance_double('User', name: 'John')
+      #
+      #   # good
+      #   instance_double(User, name: 'John')
+      #
+      class StringAsInstanceDoubleConstant < Base
+        extend AutoCorrector
+
+        MSG = 'Do not use a string as `instance_double` constant.'
+        RESTRICT_ON_SEND = %i[instance_double].freeze
+
+        # @!method stringified_instance_double_const?(node)
+        def_node_matcher :stringified_instance_double_const?, <<~PATTERN
+          (send nil? :instance_double $str ...)
+        PATTERN
+
+        def on_send(node)
+          stringified_instance_double_const?(node) do |args_node|
+            add_offense(args_node) do |corrector|
+              autocorrect(corrector, args_node)
+            end
+          end
+        end
+
+        def autocorrect(corrector, node)
+          corrector.replace(node, node.value)
+        end
+      end
+    end
+  end
+end

lib/rubocop/cop/rspec/unspecified_exception.rb

@@ -62,7 +62,10 @@ def empty_exception_matcher?(node)
         end
 
         def find_expect_to(node)
-          node.each_ancestor(:send).find do |ancestor|
+          node.each_ancestor.find do |ancestor|
+            break if ancestor.block_type?
+            next unless ancestor.send_type?
+
             expect_to?(ancestor)
           end
         end

lib/rubocop/cop/rspec_cops.rb

@@ -99,6 +99,7 @@
 require_relative 'rspec/sort_metadata'
 require_relative 'rspec/spec_file_path_format'
 require_relative 'rspec/spec_file_path_suffix'
+require_relative 'rspec/string_as_instance_double_constant'
 require_relative 'rspec/stubbed_mock'
 require_relative 'rspec/subject_declaration'
 require_relative 'rspec/subject_stub'

spec/rubocop/cop/rspec/string_as_instance_double_constant_spec.rb

@@ -0,0 +1,33 @@
+# frozen_string_literal: true
+
+RSpec.describe RuboCop::Cop::RSpec::StringAsInstanceDoubleConstant,
+               :config do
+  context 'when using a class for instance_double' do
+    it 'does not register an offense' do
+      expect_no_offenses(<<~RUBY)
+        instance_double(Shape, area: 12)
+      RUBY
+    end
+  end
+
+  context 'when passing a variable to initialize instance_double' do
+    it 'does not register an offense' do
+      expect_no_offenses(<<~RUBY)
+        instance_double(type_undetectable_in_static_analysis)
+      RUBY
+    end
+  end
+
+  context 'when using a string for instance_double' do
+    it 'replaces the string with the class' do
+      expect_offense <<~RUBY
+        instance_double('Shape', area: 12)
+                        ^^^^^^^ Do not use a string as `instance_double` constant.
+      RUBY
+
+      expect_correction <<~RUBY
+        instance_double(Shape, area: 12)
+      RUBY
+    end
+  end
+end

spec/rubocop/cop/rspec/unspecified_exception_spec.rb

@@ -85,6 +85,30 @@
         }.to raise_error(my_exception)
       RUBY
     end
+
+    it 'allows a subject function to be named raise_error' do
+      expect_no_offenses(<<~RUBY)
+        def raise_exception
+          raise StandardError
+        end
+
+        expect {
+          raise_error
+        }.to raise_error(StandardError)
+      RUBY
+    end
+
+    it 'allows a subject function to be named raise_exception' do
+      expect_no_offenses(<<~RUBY)
+        def raise_exception
+          raise StandardError
+        end
+
+        expect {
+          raise_exception
+        }.to raise_error(StandardError)
+      RUBY
+    end
   end
 
   context 'with raise_exception matcher' do
@@ -198,5 +222,37 @@
                                 ^^^^^^^^^^^^^^^ Specify the exception being captured
       RUBY
     end
+
+    it 'does not confuse blocks with chains' do
+      expect_no_offenses(<<~RUBY)
+        expect do
+          expect { foo }.not_to raise_error
+        end.to change(Foo, :count).by(3)
+      RUBY
+    end
+
+    it 'allows a subject function to be named raise_exception' do
+      expect_no_offenses(<<~RUBY)
+        def raise_error
+          raise StandardError
+        end
+
+        expect {
+          raise_exception
+        }.to raise_exception(StandardError)
+      RUBY
+    end
+
+    it 'allows a subject function to be named raise_error' do
+      expect_no_offenses(<<~RUBY)
+        def raise_error
+          raise StandardError
+        end
+
+        expect {
+          raise_error
+        }.to raise_exception(StandardError)
+      RUBY
+    end
   end
 end