From 00f5c5c41b3283507163131f704cb3a77eb3bd26 Mon Sep 17 00:00:00 2001
From: Ted Johansson <drenmi@gmail.com>
Date: Mon, 11 Feb 2019 11:36:24 +0800
Subject: [PATCH] [Fix #6755] Prevent Style/TrailingCommaInArgument from
 breaking when a safe method call is chained on the offending method

This cop would error out on code like:

```
foo.bar(
  baz: 1,
)&.fetch(:qux)
```

This was happening because the cop wasn't taking `csend` (safe navigation)
node types into consideration.
---
 CHANGELOG.md                                    |  4 ++++
 lib/rubocop/cop/mixin/trailing_comma.rb         |  2 +-
 .../style/trailing_comma_in_arguments_spec.rb   | 17 +++++++++++++++++
 3 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 473e3227383..d6bdc21ed0f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,10 @@
 
 ## 0.64.0 (2019-02-10)
 
+### Bug fixes
+
+* [#6755](https://github.com/rubocop-hq/rubocop/issues/6755): Prevent `Style/TrailingCommaInArgument` from breaking when a safe method call is chained on the offending method. ([@drenmi][])
+
 ### New features
 
 * [#6704](https://github.com/rubocop-hq/rubocop/pull/6704): Add new `Rails/ReflectionClassName` cop. ([@Bhacaz][])
diff --git a/lib/rubocop/cop/mixin/trailing_comma.rb b/lib/rubocop/cop/mixin/trailing_comma.rb
index 4f8819dc983..f9754b07cef 100644
--- a/lib/rubocop/cop/mixin/trailing_comma.rb
+++ b/lib/rubocop/cop/mixin/trailing_comma.rb
@@ -104,7 +104,7 @@ def allowed_multiline_argument?(node)
       end
 
       def elements(node)
-        return node.children unless node.send_type?
+        return node.children unless %i[csend send].include?(node.type)
 
         node.arguments.flat_map do |argument|
           # For each argument, if it is a multi-line hash without braces,
diff --git a/spec/rubocop/cop/style/trailing_comma_in_arguments_spec.rb b/spec/rubocop/cop/style/trailing_comma_in_arguments_spec.rb
index a781a60f50d..77e0b30776b 100644
--- a/spec/rubocop/cop/style/trailing_comma_in_arguments_spec.rb
+++ b/spec/rubocop/cop/style/trailing_comma_in_arguments_spec.rb
@@ -416,6 +416,23 @@
           )
         RUBY
       end
+
+      it 'does not break when a method call is chaned on the offending one' do
+        expect_no_offenses(<<-RUBY.strip_indent)
+          foo.bar(
+            baz: 1,
+          ).fetch(:qux)
+        RUBY
+      end
+
+      it 'does not break when a safe method call is chained on the ' \
+         'offending one', :ruby23 do
+        expect_no_offenses(<<-RUBY.strip_indent)
+          foo.bar(
+            baz: 1,
+          )&.fetch(:qux)
+        RUBY
+      end
     end
 
     context 'when EnforcedStyleForMultiline is consistent_comma' do