Add new RSpec/MissingExpectationTargetMethod cop

.rubocop.yml

@@ -283,6 +283,8 @@ RSpec/MatchArray:
   Enabled: true
 RSpec/MetadataStyle:
   Enabled: true
+RSpec/MissingExpectationTargetMethod:
+  Enabled: true
 RSpec/NoExpectationExample:
   Enabled: true
 RSpec/PendingWithoutReason:

CHANGELOG.md

@@ -9,6 +9,7 @@
 - Remove `RSpec/Capybara/FeatureMethods` cop. If you are using this cop, change it to use `RSpec/Dialect`. ([@ydah])
 - Support `AutoCorrect: contextual` option for LSP. ([@ydah])
 - Enable all pending cops. ([@bquorning])
+- Add new `RSpec/MissingExpectationTargetMethod` cop. ([@krororo])
 
 ## 2.29.2 (2024-05-02)
 
@@ -924,6 +925,7 @@ Compatibility release so users can upgrade RuboCop to 0.51.0. No new features.
 [@k-s-a]: https://github.com/K-S-A
 [@kellysutton]: https://github.com/kellysutton
 [@koic]: https://github.com/koic
+[@krororo]: https://github.com/krororo
 [@kuahyeow]: https://github.com/kuahyeow
 [@lazycoder9]: https://github.com/lazycoder9
 [@leoarnold]: https://github.com/leoarnold

config/default.yml

@@ -657,6 +657,12 @@ RSpec/MissingExampleGroupArgument:
   VersionAdded: '1.28'
   Reference: https://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/MissingExampleGroupArgument
 
+RSpec/MissingExpectationTargetMethod:
+  Description: Checks if `.to`, `not_to` or `to_not` are used.
+  Enabled: pending
+  VersionAdded: "<<next>>"
+  Reference: https://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/MissingExpectationTargetMethod
+
 RSpec/MultipleDescribes:
   Description: Checks for multiple top-level example groups.
   Enabled: true

docs/modules/ROOT/pages/cops.adoc

@@ -66,6 +66,7 @@
 * xref:cops_rspec.adoc#rspecmessagespies[RSpec/MessageSpies]
 * xref:cops_rspec.adoc#rspecmetadatastyle[RSpec/MetadataStyle]
 * xref:cops_rspec.adoc#rspecmissingexamplegroupargument[RSpec/MissingExampleGroupArgument]
+* xref:cops_rspec.adoc#rspecmissingexpectationtargetmethod[RSpec/MissingExpectationTargetMethod]
 * xref:cops_rspec.adoc#rspecmultipledescribes[RSpec/MultipleDescribes]
 * xref:cops_rspec.adoc#rspecmultipleexpectations[RSpec/MultipleExpectations]
 * xref:cops_rspec.adoc#rspecmultiplememoizedhelpers[RSpec/MultipleMemoizedHelpers]

docs/modules/ROOT/pages/cops_rspec.adoc

@@ -3406,6 +3406,42 @@ end
 
 * https://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/MissingExampleGroupArgument
 
+== RSpec/MissingExpectationTargetMethod
+
+|===
+| Enabled by default | Safe | Supports autocorrection | Version Added | Version Changed
+
+| Pending
+| Yes
+| No
+| <<next>>
+| -
+|===
+
+Checks if `.to`, `not_to` or `to_not` are used.
+
+The RSpec::Expectations::ExpectationTarget must use `to`, `not_to` or
+`to_not` to run. Therefore, this cop checks if other methods are used.
+
+=== Examples
+
+[source,ruby]
+----
+# bad
+expect(something).kind_of? Foo
+is_expected == 42
+expect{something}.eq? BarError
+
+# good
+expect(something).to be_a Foo
+is_expected.to eq 42
+expect{something}.to raise_error BarError
+----
+
+=== References
+
+* https://www.rubydoc.info/gems/rubocop-rspec/RuboCop/Cop/RSpec/MissingExpectationTargetMethod
+
 == RSpec/MultipleDescribes
 
 |===

lib/rubocop/cop/rspec/missing_expectation_target_method.rb

@@ -0,0 +1,54 @@
+# frozen_string_literal: true
+
+module RuboCop
+  module Cop
+    module RSpec
+      # Checks if `.to`, `not_to` or `to_not` are used.
+      #
+      # The RSpec::Expectations::ExpectationTarget must use `to`, `not_to` or
+      # `to_not` to run. Therefore, this cop checks if other methods are used.
+      #
+      # @example
+      #   # bad
+      #   expect(something).kind_of? Foo
+      #   is_expected == 42
+      #   expect{something}.eq? BarError
+      #
+      #   # good
+      #   expect(something).to be_a Foo
+      #   is_expected.to eq 42
+      #   expect{something}.to raise_error BarError
+      #
+      class MissingExpectationTargetMethod < Base
+        MSG = 'Use `.to`, `.not_to` or `.to_not` to set an expectation.'
+        RESTRICT_ON_SEND = %i[expect is_expected].freeze
+
+        # @!method expect?(node)
+        def_node_matcher :expect?, <<~PATTERN
+          {
+            (send nil? :expect ...)
+            (send nil? :is_expected)
+          }
+        PATTERN
+
+        # @!method expect_block?(node)
+        def_node_matcher :expect_block?, <<~PATTERN
+          (block #expect? (args) _body)
+        PATTERN
+
+        # @!method expectation_without_runner?(node)
+        def_node_matcher :expectation_without_runner?, <<~PATTERN
+          (send {#expect? #expect_block?} !#Runners.all ...)
+        PATTERN
+
+        def on_send(node)
+          node = node.parent if node.parent&.block_type?
+
+          expectation_without_runner?(node.parent) do
+            add_offense(node.parent.loc.selector)
+          end
+        end
+      end
+    end
+  end
+end

lib/rubocop/cop/rspec_cops.rb

@@ -64,6 +64,7 @@
 require_relative 'rspec/message_spies'
 require_relative 'rspec/metadata_style'
 require_relative 'rspec/missing_example_group_argument'
+require_relative 'rspec/missing_expectation_target_method'
 require_relative 'rspec/multiple_describes'
 require_relative 'rspec/multiple_expectations'
 require_relative 'rspec/multiple_memoized_helpers'

spec/rubocop/cop/rspec/missing_expectation_target_method_spec.rb

@@ -0,0 +1,81 @@
+# frozen_string_literal: true
+
+RSpec.describe RuboCop::Cop::RSpec::MissingExpectationTargetMethod do
+  it 'registers offenses to other than `to` or `not_to`' do
+    expect_offense(<<~RUBY)
+      it 'something' do
+        something = 1
+        expect(something).kind_of? Integer
+                          ^^^^^^^^ Use `.to`, `.not_to` or `.to_not` to set an expectation.
+      end
+    RUBY
+  end
+
+  it 'registers offenses to other than `to` or `not_to` ' \
+     'when block has one expression' do
+    expect_offense(<<~RUBY)
+      it 'something' do
+        expect(something).eq? 42
+                          ^^^ Use `.to`, `.not_to` or `.to_not` to set an expectation.
+      end
+    RUBY
+  end
+
+  it 'registers offenses to other than `to` or `not_to` with `is_expected`' do
+    expect_offense(<<~RUBY)
+      it 'something' do
+        is_expected == 42
+                    ^^ Use `.to`, `.not_to` or `.to_not` to set an expectation.
+      end
+    RUBY
+  end
+
+  it 'registers offenses to other than `to` or `not_to` with block' do
+    expect_offense(<<~RUBY)
+      it 'something' do
+        expect{something}.kind_of? StandardError
+                          ^^^^^^^^ Use `.to`, `.not_to` or `.to_not` to set an expectation.
+      end
+    RUBY
+  end
+
+  it 'accepts void `expect`' do
+    expect_no_offenses(<<~RUBY)
+      it 'something' do
+        expect(something)
+      end
+    RUBY
+  end
+
+  it 'accepts only `expect`' do
+    expect_no_offenses(<<~RUBY)
+      expect
+    RUBY
+  end
+
+  %w[to not_to to_not].each do |method|
+    it "accepts `.#{method}`" do
+      expect_no_offenses(<<~RUBY)
+        it 'something' do
+          expect(something).#{method} be_a Integer
+        end
+      RUBY
+    end
+
+    it "accepts `.#{method}` with `is_expected`" do
+      expect_no_offenses(<<~RUBY)
+        it 'something' do
+          is_expected.#{method} eq 42
+        end
+      RUBY
+    end
+
+    it "accepts `.#{method}` with block" do
+      expect_no_offenses(<<~RUBY)
+        it 'something' do
+          expect{something}.#{method} raise_error(StandardError)
+        end
+      RUBY
+    end
+  end
+end