Merge pull request #858 from rubocop-hq/expect_actual-autocorrect

Adds an autocorrect to `RSpec/ExpectActual`, swapping the arguments to `expect` and matcher when possible.

Author: pirj

CHANGELOG.md

@@ -4,6 +4,7 @@
 
 * Fix `RSpec/InstanceVariable` detection inside custom matchers. ([@pirj][])
 * Fix `RSpec/ScatteredSetup` to distinguish hooks with different metadata. ([@pirj][])
+* Add autocorrect support for `RSpec/ExpectActual` cop. ([@dduugg][], [@pirj][])
 
 ## 1.37.1 (2019-12-16)
 
@@ -475,3 +476,4 @@ Compatibility release so users can upgrade RuboCop to 0.51.0. No new features.
 [@mkrawc]: https://github.com/mkrawc
 [@jfragoulis]: https://github.com/jfragoulis
 [@ybiquitous]: https://github.com/ybiquitous
+[@dduugg]: https://github.com/dduugg

lib/rubocop/cop/rspec/expect_actual.rb

@@ -41,11 +41,31 @@ class ExpectActual < Cop
           regexp
         ].freeze
 
-        def_node_matcher :expect_literal, '(send _ :expect $#literal?)'
+        SUPPORTED_MATCHERS = %i[eq eql equal be].freeze
+
+        def_node_matcher :expect_literal, <<~PATTERN
+          (send
+            (send nil? :expect $#literal?)
+            #{Runners::ALL.node_pattern_union}
+            {
+              (send (send nil? $:be) :== $_)
+              (send nil? $_ $_ ...)
+            }
+          )
+        PATTERN
 
         def on_send(node)
           expect_literal(node) do |argument|
-            add_offense(argument)
+            add_offense(node, location: argument.source_range)
+          end
+        end
+
+        def autocorrect(node)
+          actual, matcher, expected = expect_literal(node)
+          lambda do |corrector|
+            return unless SUPPORTED_MATCHERS.include?(matcher)
+
+            swap(corrector, actual, expected)
           end
         end
 
@@ -65,6 +85,11 @@ def complex_literal?(node)
           COMPLEX_LITERALS.include?(node.type) &&
             node.each_child_node.all?(&method(:literal?))
         end
+
+        def swap(corrector, actual, expected)
+          corrector.replace(actual.source_range, expected.source)
+          corrector.replace(expected.source_range, actual.source)
+        end
       end
     end
   end

manual/cops_rspec.md

@@ -977,7 +977,7 @@ IgnoredWords | `[]` | Array
 
 Enabled by default | Supports autocorrection
 --- | ---
-Enabled | No
+Enabled | Yes
 
 Checks for `expect(...)` calls containing literal values.
 

spec/rubocop/cop/rspec/expect_actual_spec.rb

@@ -18,6 +18,17 @@
         end
       end
     RUBY
+
+    expect_correction(<<-RUBY)
+      describe Foo do
+        it 'uses expect incorrectly' do
+          expect(bar).to eq(123)
+          expect(bar).to eq(12.3)
+          expect(bar).to eq(1i)
+          expect(bar).to eq(1r)
+        end
+      end
+    RUBY
   end
 
   it 'flags boolean literal values within expect(...)' do
@@ -31,6 +42,15 @@
         end
       end
     RUBY
+
+    expect_correction(<<-RUBY)
+      describe Foo do
+        it 'uses expect incorrectly' do
+          expect(bar).to eq(true)
+          expect(bar).to eq(false)
+        end
+      end
+    RUBY
   end
 
   it 'flags string and symbol literal values within expect(...)' do
@@ -44,6 +64,15 @@
         end
       end
     RUBY
+
+    expect_correction(<<-RUBY)
+      describe Foo do
+        it 'uses expect incorrectly' do
+          expect(bar).to eq("foo")
+          expect(bar).to eq(:foo)
+        end
+      end
+    RUBY
   end
 
   it 'flags literal nil value within expect(...)' do
@@ -55,6 +84,14 @@
         end
       end
     RUBY
+
+    expect_correction(<<-RUBY)
+      describe Foo do
+        it 'uses expect incorrectly' do
+          expect(bar).to eq(nil)
+        end
+      end
+    RUBY
   end
 
   it 'does not flag dynamic values within expect(...)' do
@@ -80,6 +117,15 @@
         end
       end
     RUBY
+
+    expect_correction(<<-RUBY)
+      describe Foo do
+        it 'uses expect incorrectly' do
+          expect(bar).to eq([123])
+          expect(bar).to eq([[123]])
+        end
+      end
+    RUBY
   end
 
   it 'flags hashes containing only literal values within expect(...)' do
@@ -93,6 +139,15 @@
         end
       end
     RUBY
+
+    expect_correction(<<-RUBY)
+      describe Foo do
+        it 'uses expect incorrectly' do
+          expect(bar).to eq(foo: 1, bar: 2)
+          expect(bar).to eq(foo: 1, bar: [{}])
+        end
+      end
+    RUBY
   end
 
   it 'flags ranges containing only literal values within expect(...)' do
@@ -106,6 +161,15 @@
         end
       end
     RUBY
+
+    expect_correction(<<-RUBY)
+      describe Foo do
+        it 'uses expect incorrectly' do
+          expect(bar).to eq(1..2)
+          expect(bar).to eq(1...2)
+        end
+      end
+    RUBY
   end
 
   it 'flags regexps containing only literal values within expect(...)' do
@@ -117,6 +181,14 @@
         end
       end
     RUBY
+
+    expect_correction(<<-RUBY)
+      describe Foo do
+        it 'uses expect incorrectly' do
+          expect(bar).to eq(/foo|bar/)
+        end
+      end
+    RUBY
   end
 
   it 'does not flag complex values with dynamic parts within expect(...)' do
@@ -135,6 +207,105 @@
     RUBY
   end
 
+  it 'ignores `be` with no argument' do
+    expect_no_offenses(<<~RUBY)
+      describe Foo do
+        it 'uses expect legitimately' do
+          expect(1).to be
+        end
+      end
+    RUBY
+  end
+
+  it 'flags `be` with an argument' do
+    expect_offense(<<~RUBY)
+      describe Foo do
+        it 'uses expect incorrectly' do
+          expect(true).to be(a)
+                 ^^^^ Provide the actual you are testing to `expect(...)`.
+        end
+      end
+    RUBY
+
+    expect_correction(<<~RUBY)
+      describe Foo do
+        it 'uses expect incorrectly' do
+          expect(a).to be(true)
+        end
+      end
+    RUBY
+  end
+
+  it 'flags `be ==`' do
+    expect_offense(<<~RUBY)
+      describe Foo do
+        it 'uses expect incorrectly' do
+          expect(1).to be == a
+                 ^ Provide the actual you are testing to `expect(...)`.
+        end
+      end
+    RUBY
+
+    expect_correction(<<~RUBY)
+      describe Foo do
+        it 'uses expect incorrectly' do
+          expect(a).to be == 1
+        end
+      end
+    RUBY
+  end
+
+  it 'flags with `eql` matcher' do
+    expect_offense(<<-RUBY)
+      describe Foo do
+        it 'uses expect incorrectly' do
+          expect(1).to eql(bar)
+                 ^ Provide the actual you are testing to `expect(...)`.
+        end
+      end
+    RUBY
+
+    expect_correction(<<-RUBY)
+      describe Foo do
+        it 'uses expect incorrectly' do
+          expect(bar).to eql(1)
+        end
+      end
+    RUBY
+  end
+
+  it 'flags with `equal` matcher' do
+    expect_offense(<<-RUBY)
+      describe Foo do
+        it 'uses expect incorrectly' do
+          expect(1).to equal(bar)
+                 ^ Provide the actual you are testing to `expect(...)`.
+        end
+      end
+    RUBY
+
+    expect_correction(<<-RUBY)
+      describe Foo do
+        it 'uses expect incorrectly' do
+          expect(bar).to equal(1)
+        end
+      end
+    RUBY
+  end
+
+  it 'flags but does not autocorrect violations for other matchers' do
+    expect_offense(<<-RUBY)
+      describe Foo do
+        it 'uses expect incorrectly' do
+          expect([1,2,3]).to include(a)
+                 ^^^^^^^ Provide the actual you are testing to `expect(...)`.
+        end
+      end
+    RUBY
+
+    expect_no_corrections
+  end
+
   context 'when inspecting rspec-rails routing specs' do
     let(:cop_config) { {} }