[Fix rubocop#142] Minitest/GlobalExpectations: autocorrect when recei…

…ver is lambda

This fixes an issue when autocorrecting offenses where the receiver is
a lambda function: `-> { n }`.
The expected correct result is `_ { n }` instead of `_ { -> { n } }`.

Fixes rubocop#142

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## master (unreleased)
 
+### Bug fixes
+
+* [#149](https://github.com/rubocop/rubocop-minitest/pull/149): Fix `Minitest/GlobalExpectations` autocorrect when receiver is lambda. ([@gi][])
+
 ## 0.15.2 (2021-10-11)
 
 ### Bug fixes
@@ -246,3 +250,4 @@
 [@tsmmark]: https://github.com/tsmmark
 [@cstyles]: https://github.com/cstyles
 [@ghiculescu]: https://github.com/ghiculescu
+[@gi]: https://github.com/gi

lib/rubocop/cop/minitest/global_expectations.rb

@@ -62,30 +62,36 @@ class GlobalExpectations < Base
           )
         PATTERN
 
+        def_node_matcher :block_lambda?, <<~PATTERN
+          (block (send nil? :lambda) (args) $_)
+        PATTERN
+
         def on_send(node)
           return unless value_global_expectation?(node) || block_global_expectation?(node)
 
           message = format(MSG, preferred: preferred_receiver(node))
 
-          add_offense(node.receiver.source_range, message: message) do |corrector|
-            receiver = node.receiver.source_range
-
-            if BLOCK_MATCHERS.include?(node.method_name)
-              corrector.wrap(receiver, '_ { ', ' }')
-            else
-              corrector.wrap(receiver, '_(', ')')
-            end
+          add_offense(node.receiver, message: message) do |corrector|
+            receiver = node.receiver
+            replacement = preferred_receiver(node)
+            corrector.replace(receiver, replacement)
           end
         end
 
         private
 
+        def preferred_method
+          :_
+        end
+
         def preferred_receiver(node)
-          source = node.receiver.source
+          receiver = node.receiver
+
           if BLOCK_MATCHERS.include?(node.method_name)
-            "_ { #{source} }"
+            body = block_lambda?(receiver) || receiver
+            "#{preferred_method} { #{body.source} }"
           else
-            "_(#{source})"
+            "#{preferred_method}(#{receiver.source})"
           end
         end
       end

test/rubocop/cop/minitest/global_expectations_test.rb

@@ -256,6 +256,21 @@ def test_works_with_chained_method_calls
       RUBY
     end
 
+    define_method(:"test_registers_offense_when_using_global_#{matcher}_and_block") do
+      assert_offense(<<~RUBY)
+        it 'does something' do
+          -> { n }.#{matcher} 42
+          ^^^^^^^^ Use `_ { n }` instead.
+        end
+      RUBY
+
+      assert_correction(<<~RUBY)
+        it 'does something' do
+          _ { n }.#{matcher} 42
+        end
+      RUBY
+    end
+
     define_method(:"test_no_offense_when_using_expect_form_of_#{matcher}") do
       assert_no_offenses(<<~RUBY)
         it 'does something' do