[Fix #8871] Fix a false positive for Style/RedundantBegin

Fixes #8871.

This PR fixes a false positive for `Style/RedundantBegin`
when using `begin` for method argument or part of conditions.

`begin` keyword may be redundant when using only one expression
in `begin` of each issue case.
However, since it is the unintended case for #8822, I think it
can be implemented as an enhancement different from this bug fix.

Author: koic

CHANGELOG.md

@@ -9,6 +9,7 @@
 * [#8869](https://github.com/rubocop-hq/rubocop/issues/8869): Fix a false positive for `Style/RedundantBegin` when using `begin` for or assignment and method call. ([@koic][])
 * [#8862](https://github.com/rubocop-hq/rubocop/issues/8862): Fix an error for `Lint/AmbiguousRegexpLiteral` when using regexp without method calls in nested structure. ([@koic][])
 * [#8872](https://github.com/rubocop-hq/rubocop/issues/8872): Fix an error for `Metrics/ClassLength` when multiple assignments to constants. ([@koic][])
+* [#8871](https://github.com/rubocop-hq/rubocop/issues/8871): Fix a false positive for `Style/RedundantBegin` when using `begin` for method argument or part of conditions. ([@koic][])
 
 ## 0.93.0 (2020-10-08)
 

lib/rubocop/cop/style/redundant_begin.rb

@@ -85,10 +85,7 @@ def on_block(node)
         end
 
         def on_kwbegin(node)
-          return if node.each_ancestor.any?(&:assignment?) || node.parent&.post_condition_loop?
-
-          first_child = node.children.first
-          return if first_child.rescue_type? || first_child.ensure_type?
+          return if contain_rescue_or_ensure?(node) || valid_context_using_only_begin?(node)
 
           register_offense(node)
         end
@@ -101,6 +98,19 @@ def register_offense(node)
             corrector.remove(node.loc.end)
           end
         end
+
+        def contain_rescue_or_ensure?(node)
+          first_child = node.children.first
+
+          first_child.rescue_type? || first_child.ensure_type?
+        end
+
+        def valid_context_using_only_begin?(node)
+          parent = node.parent
+
+          node.each_ancestor.any?(&:assignment?) || parent&.post_condition_loop? ||
+            parent&.send_type? || parent&.operator_keyword?
+        end
       end
     end
   end

spec/rubocop/cop/style/redundant_begin_spec.rb

@@ -233,6 +233,33 @@ def method
     RUBY
   end
 
+  it 'does not register an offense when using `begin` for method argument' do
+    expect_no_offenses(<<~RUBY)
+      do_something begin
+        foo
+        bar
+      end
+    RUBY
+  end
+
+  it 'does not register an offense when using `begin` for logical operator conditions' do
+    expect_no_offenses(<<~RUBY)
+      condition && begin
+        foo
+        bar
+      end
+    RUBY
+  end
+
+  it 'does not register an offense when using `begin` for semantic operator conditions' do
+    expect_no_offenses(<<~RUBY)
+      condition and begin
+        foo
+        bar
+      end
+    RUBY
+  end
+
   context '< Ruby 2.5', :ruby24 do
     it 'accepts a do-end block with a begin-end' do
       expect_no_offenses(<<~RUBY)