From 9cf9ceb1d48aae5149b4b7b63918c983aa694aca Mon Sep 17 00:00:00 2001
From: Koichi ITO <koic.ito@gmail.com>
Date: Mon, 20 Jul 2020 19:06:44 +0900
Subject: [PATCH] Fix an infinite loop error for `Style/EmptyMethod`

This PR fixes the following infinite loop error for `Style/EmptyMethod`.

```ruby
% cat example.rb
def foo(arg
    ); end
```

## Before

The following error occurs without auto-correction.

```console
% bundle exec rubocop --only Style/EmptyMethod -a example.rb
(snip)

Offenses:

example.rb:1:1: C: [Corrected] Style/EmptyMethod: Put empty method
definitions on a single line.
def foo(arg ...
^^^^^^^^^^^^

0 files inspected, 1 offense detected, 1 offense corrected
Infinite loop detected in
/Users/koic/src/github.com/koic/rubocop-issues/empty_method/example.rb.
/Users/koic/src/github.com/rubocop-hq/rubocop/lib/rubocop/runner.rb:288:in `check_for_infinite_loop'
/Users/koic/src/github.com/rubocop-hq/rubocop/lib/rubocop/runner.rb:271:in `block in iterate_until_no_changes'
/Users/koic/src/github.com/rubocop-hq/rubocop/lib/rubocop/runner.rb:270:in `loop'
/Users/koic/src/github.com/rubocop-hq/rubocop/lib/rubocop/runner.rb:270:in `iterate_until_no_changes'
/Users/koic/src/github.com/rubocop-hq/rubocop/lib/rubocop/runner.rb:241:in `do_inspection_loop'
(snip)

% cat example.rb
def foo(arg
    ); end
```

## After

Auto-corrects without any error.

```console
% bundle exec rubocop --only Style/EmptyMethod -a example.rb
(snip)

Offenses:

example.rb:1:1: C: [Corrected] Style/EmptyMethod: Put empty method
definitions on a single line.
def foo(arg ...
^^^^^^^^^^^^

1 file inspected, 1 offense detected, 1 offense corrected

% cat example.rb
def foo(arg); end
```
---
 CHANGELOG.md                                |  1 +
 lib/rubocop/cop/style/empty_method.rb       | 10 +++++-----
 spec/rubocop/cop/style/empty_method_spec.rb |  5 +++++
 3 files changed, 11 insertions(+), 5 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 029d08fbde9..efede0b2cb8 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -16,6 +16,7 @@
 * [#8299](https://github.com/rubocop-hq/rubocop/issues/8299): Fix an incorrect auto-correct for `Style/RedundantCondition` when using `raise`, `rescue`, or `and` without argument parentheses in `else`. ([@koic][])
 * [#8335](https://github.com/rubocop-hq/rubocop/issues/8335): Fix incorrect character class detection for nested or POSIX bracket character classes in `Style/RedundantRegexpEscape`. ([@owst][])
 * [#8347](https://github.com/rubocop-hq/rubocop/issues/8347): Fix an incorrect auto-correct for `EnforcedStyle: hash_rockets` of `Style/HashSyntax` with `Layout/HashAlignment`. ([@koic][])
+* [#8375](https://github.com/rubocop-hq/rubocop/pull/8375): Fix an infinite loop error for `Style/EmptyMethod`. ([@koic][])
 
 ### Changes
 
diff --git a/lib/rubocop/cop/style/empty_method.rb b/lib/rubocop/cop/style/empty_method.rb
index 07b47350e12..2dfe32c3bce 100644
--- a/lib/rubocop/cop/style/empty_method.rb
+++ b/lib/rubocop/cop/style/empty_method.rb
@@ -73,13 +73,13 @@ def correct_style?(node)
         end
 
         def corrected(node)
-          if node.arguments?
-            arguments   = node.arguments.source
-            extra_space = ' ' unless parentheses?(node.arguments)
-          end
           scope = node.receiver ? "#{node.receiver.source}." : ''
+          arguments = if node.arguments?
+                        args = node.arguments.map(&:source).join(', ')
 
-          signature = [scope, node.method_name, extra_space, arguments].join
+                        parentheses?(node.arguments) ? "(#{args})" : " #{args}"
+                      end
+          signature = [scope, node.method_name, arguments].join
 
           ["def #{signature}", 'end'].join(joint(node))
         end
diff --git a/spec/rubocop/cop/style/empty_method_spec.rb b/spec/rubocop/cop/style/empty_method_spec.rb
index 3d350c7abbc..e76094fed46 100644
--- a/spec/rubocop/cop/style/empty_method_spec.rb
+++ b/spec/rubocop/cop/style/empty_method_spec.rb
@@ -61,6 +61,11 @@
                        'end'].join("\n"),
                       'def foo; end'
 
+      it_behaves_like 'code with offense',
+                      ['def foo(arg',
+                       '); end'].join("\n"),
+                      'def foo(arg); end'
+
       it_behaves_like 'code without offense',
                       'def foo; end'
     end