From 04442ec4699cc3cdf09abf1351331a7e02155be0 Mon Sep 17 00:00:00 2001
From: Koichi ITO <koic.ito@gmail.com>
Date: Mon, 13 Jun 2022 19:09:36 +0900
Subject: [PATCH] [Fix #10711] Fix an error for
 `Style/MultilineTernaryOperator`

Fixes #10711.

This PR fixes an error for `Style/MultilineTernaryOperator`
when the false branch is on a separate line.
---
 ...ror_for_style_multiline_ternary_operator.md |  1 +
 .../cop/style/multiline_ternary_operator.rb    |  2 +-
 .../style/multiline_ternary_operator_spec.rb   | 18 +++++++++++++++++-
 3 files changed, 19 insertions(+), 2 deletions(-)
 create mode 100644 changelog/fix_an_error_for_style_multiline_ternary_operator.md

diff --git a/changelog/fix_an_error_for_style_multiline_ternary_operator.md b/changelog/fix_an_error_for_style_multiline_ternary_operator.md
new file mode 100644
index 00000000000..92f86f3d7cb
--- /dev/null
+++ b/changelog/fix_an_error_for_style_multiline_ternary_operator.md
@@ -0,0 +1 @@
+* [#10711](https://github.com/rubocop/rubocop/issues/10711): Fix an error for `Style/MultilineTernaryOperator` when the false branch is on a separate line. ([@koic][])
diff --git a/lib/rubocop/cop/style/multiline_ternary_operator.rb b/lib/rubocop/cop/style/multiline_ternary_operator.rb
index bfeb1cf8de0..fe769960812 100644
--- a/lib/rubocop/cop/style/multiline_ternary_operator.rb
+++ b/lib/rubocop/cop/style/multiline_ternary_operator.rb
@@ -73,7 +73,7 @@ def replacement(node)
         end
 
         def enforce_single_line_ternary_operator?(node)
-          SINGLE_LINE_TYPES.include?(node.parent.type) && !use_assignment_method?(node.parent)
+          SINGLE_LINE_TYPES.include?(node.parent&.type) && !use_assignment_method?(node.parent)
         end
 
         def use_assignment_method?(node)
diff --git a/spec/rubocop/cop/style/multiline_ternary_operator_spec.rb b/spec/rubocop/cop/style/multiline_ternary_operator_spec.rb
index 29059b00c0c..1e48855b034 100644
--- a/spec/rubocop/cop/style/multiline_ternary_operator_spec.rb
+++ b/spec/rubocop/cop/style/multiline_ternary_operator_spec.rb
@@ -18,7 +18,7 @@
     RUBY
   end
 
-  it 'registers an offense and corrects when the false branch is on a separate line' do
+  it 'registers an offense and corrects when the false branch is on a separate line and assigning a return value' do
     expect_offense(<<~RUBY)
       a = cond ? b :
           ^^^^^^^^^^ Avoid multi-line ternary operators, use `if` or `unless` instead.
@@ -34,6 +34,22 @@
     RUBY
   end
 
+  it 'registers an offense and corrects when the false branch is on a separate line' do
+    expect_offense(<<~RUBY)
+      cond ? b :
+      ^^^^^^^^^^ Avoid multi-line ternary operators, use `if` or `unless` instead.
+      c
+    RUBY
+
+    expect_correction(<<~RUBY)
+      if cond
+        b
+      else
+        c
+      end
+    RUBY
+  end
+
   it 'registers an offense and corrects when everything is on a separate line' do
     expect_offense(<<~RUBY)
       a = cond ?