From 4d058aa8c2651bf2d59f554281a8fe9545b39c0d Mon Sep 17 00:00:00 2001
From: Koichi ITO <koic.ito@gmail.com>
Date: Tue, 9 Jan 2024 19:27:09 +0900
Subject: [PATCH] [Fix #12603] Fix an infinite loop error for
 `Style/MultilineTernaryOperator`

Fixes #12603.

This PR fixes an infinite loop error for `Style/MultilineTernaryOperator`
when using a method call as a ternary operator condition with a line break
between receiver and method.
---
 ...sitive_for_style_multiline_ternary_operator.md |  1 +
 .../cop/style/multiline_ternary_operator.rb       |  4 +---
 spec/rubocop/cli/autocorrect_spec.rb              | 15 +++++++++++++++
 .../cop/style/multiline_ternary_operator_spec.rb  |  9 +++++++++
 4 files changed, 26 insertions(+), 3 deletions(-)
 create mode 100644 changelog/fix_a_false_positive_for_style_multiline_ternary_operator.md

diff --git a/changelog/fix_a_false_positive_for_style_multiline_ternary_operator.md b/changelog/fix_a_false_positive_for_style_multiline_ternary_operator.md
new file mode 100644
index 000000000000..a011bb855fe4
--- /dev/null
+++ b/changelog/fix_a_false_positive_for_style_multiline_ternary_operator.md
@@ -0,0 +1 @@
+* [#12603](https://github.com/rubocop/rubocop/issues/12603): Fix an infinite loop error for `Style/MultilineTernaryOperator` when using a method call as a ternary operator condition with a line break between receiver and method. ([@koic][])
diff --git a/lib/rubocop/cop/style/multiline_ternary_operator.rb b/lib/rubocop/cop/style/multiline_ternary_operator.rb
index e9a375bed8ca..23a656eed724 100644
--- a/lib/rubocop/cop/style/multiline_ternary_operator.rb
+++ b/lib/rubocop/cop/style/multiline_ternary_operator.rb
@@ -54,12 +54,10 @@ def on_if(node)
         private
 
         def offense?(node)
-          node.ternary? && node.multiline?
+          node.ternary? && node.multiline? && node.source != replacement(node)
         end
 
         def autocorrect(corrector, node)
-          return unless offense?(node)
-
           corrector.replace(node, replacement(node))
           return unless (parent = node.parent)
           return unless (comments_in_condition = comments_in_condition(node))
diff --git a/spec/rubocop/cli/autocorrect_spec.rb b/spec/rubocop/cli/autocorrect_spec.rb
index 0bbde744e18a..c356e5f3b504 100644
--- a/spec/rubocop/cli/autocorrect_spec.rb
+++ b/spec/rubocop/cli/autocorrect_spec.rb
@@ -2971,6 +2971,21 @@ module Foo#{trailing_whitespace}
     RUBY
   end
 
+  it 'does not cause an infinite loop error for `Style/MultilineTernaryOperator`' do
+    source_file = Pathname('example.rb')
+    create_file(source_file, <<~RUBY)
+      do_something(arg
+                     .foo ? bar : baz)
+    RUBY
+
+    status = cli.run(%w[--autocorrect-all --only Style/MultilineTernaryOperator])
+    expect(status).to eq(0)
+    expect(source_file.read).to eq(<<~RUBY)
+      do_something(arg
+                     .foo ? bar : baz)
+    RUBY
+  end
+
   it 'respects `Lint/ConstantResolution` over `Style/RedundantConstantBase` when enabling`Lint/ConstantResolution`' do
     source_file = Pathname('example.rb')
     create_file(source_file, <<~RUBY)
diff --git a/spec/rubocop/cop/style/multiline_ternary_operator_spec.rb b/spec/rubocop/cop/style/multiline_ternary_operator_spec.rb
index 1fc189ee1b05..51848de34cf2 100644
--- a/spec/rubocop/cop/style/multiline_ternary_operator_spec.rb
+++ b/spec/rubocop/cop/style/multiline_ternary_operator_spec.rb
@@ -124,6 +124,15 @@
     RUBY
   end
 
+  it 'does not register an offense when using a method call as a ternary operator condition with a line break ' \
+     'between receiver and method' do
+    # NOTE: Redundant line break is corrected by `Layout/RedundantLineBreak`.
+    expect_no_offenses(<<~RUBY)
+      do_something(arg
+                     .foo ? bar : baz)
+    RUBY
+  end
+
   it 'registers an offense and corrects when returning a multiline ternary operator expression with `return`' do
     expect_offense(<<~RUBY)
       return cond ?