[Fix rubocop#8782] Mark any condition with defined? as an unsafe auto…

…correction if it is not parenthesized.

Without parens, `defined?` will apply to the entire ternary instead of its previous argument, which makes this autocorrection incorrect.

CHANGELOG.md

@@ -2,6 +2,10 @@
 
 ## master (unreleased)
 
+### Bug fixes
+
+* [#8782](https://github.com/rubocop-hq/rubocop/issues/8782): Fix incorrect autocorrection for `Style/TernaryParentheses` with `defined?`. ([@dvandersluis][])
+
 ## 0.93.0 (2020-10-08)
 
 ### New features

lib/rubocop/cop/style/ternary_parentheses.rb

@@ -192,7 +192,7 @@ def below_ternary_precedence?(child)
         end
 
         def_node_matcher :method_name, <<~PATTERN
-          {($:defined? (send nil? _) ...)
+          {($:defined? _ ...)
            (send {_ nil?} $_ _ ...)}
         PATTERN
 

spec/rubocop/cop/style/ternary_parentheses_spec.rb

@@ -159,6 +159,50 @@
           not (bar) ? a : b
         RUBY
       end
+
+      it 'registers an offense for defined? with variable in condition' do
+        expect_offense(<<~RUBY)
+          foo = defined?(bar) ? a : b
+                ^^^^^^^^^^^^^^^^^^^^^ Use parentheses for ternary conditions.
+        RUBY
+
+        expect_correction(<<~RUBY)
+          foo = (defined?(bar)) ? a : b
+        RUBY
+      end
+
+      it 'registers an offense for defined? with method chain in condition' do
+        expect_offense(<<~RUBY)
+          foo = defined?(bar.baz) ? a : b
+                ^^^^^^^^^^^^^^^^^^^^^^^^^ Use parentheses for ternary conditions.
+        RUBY
+
+        expect_correction(<<~RUBY)
+          foo = (defined?(bar.baz)) ? a : b
+        RUBY
+      end
+
+      it 'registers an offense for defined? with class method in condition' do
+        expect_offense(<<~RUBY)
+          foo = defined?(Bar.baz) ? a : b
+                ^^^^^^^^^^^^^^^^^^^^^^^^^ Use parentheses for ternary conditions.
+        RUBY
+
+        expect_correction(<<~RUBY)
+          foo = (defined?(Bar.baz)) ? a : b
+        RUBY
+      end
+
+      it 'registers an offense for defined? with nested constant in condition' do
+        expect_offense(<<~RUBY)
+          foo = defined?(Bar::BAZ) ? a : b
+                ^^^^^^^^^^^^^^^^^^^^^^^^^^ Use parentheses for ternary conditions.
+        RUBY
+
+        expect_correction(<<~RUBY)
+          foo = (defined?(Bar::BAZ)) ? a : b
+        RUBY
+      end
     end
 
     context 'with an assignment condition' do
@@ -327,6 +371,42 @@
 
         expect_no_corrections
       end
+
+      it 'registers an offense for defined with variable in condition' do
+        expect_offense(<<~RUBY)
+          foo = (defined? bar) ? a : b
+                ^^^^^^^^^^^^^^^^^^^^^^ Omit parentheses for ternary conditions.
+        RUBY
+
+        expect_no_corrections
+      end
+
+      it 'registers an offense for defined with method chain in condition' do
+        expect_offense(<<~RUBY)
+          foo = (defined? bar.baz) ? a : b
+                ^^^^^^^^^^^^^^^^^^^^^^^^^^ Omit parentheses for ternary conditions.
+        RUBY
+
+        expect_no_corrections
+      end
+
+      it 'registers an offense for defined with class method in condition' do
+        expect_offense(<<~RUBY)
+          foo = (defined? Bar.baz) ? a : b
+                ^^^^^^^^^^^^^^^^^^^^^^^^^^ Omit parentheses for ternary conditions.
+        RUBY
+
+        expect_no_corrections
+      end
+
+      it 'registers an offense for defined with nested constant in condition' do
+        expect_offense(<<~RUBY)
+          foo = (defined? Bar::BAZ) ? a : b
+                ^^^^^^^^^^^^^^^^^^^^^^^^^^^ Omit parentheses for ternary conditions.
+        RUBY
+
+        expect_no_corrections
+      end
     end
 
     context 'with an assignment condition' do
@@ -521,6 +601,42 @@
       it 'accepts boolean expression' do
         expect_no_offenses('foo = (bar && (baz || bar)) ? a : b')
       end
+
+      it 'registers an offense for defined with variable in condition' do
+        expect_offense(<<~RUBY)
+          foo = (defined? bar) ? a : b
+                ^^^^^^^^^^^^^^^^^^^^^^ Only use parentheses for ternary expressions with complex conditions.
+        RUBY
+
+        expect_no_corrections
+      end
+
+      it 'registers an offense for defined with method chain in condition' do
+        expect_offense(<<~RUBY)
+          foo = (defined? bar.baz) ? a : b
+                ^^^^^^^^^^^^^^^^^^^^^^^^^^ Only use parentheses for ternary expressions with complex conditions.
+        RUBY
+
+        expect_no_corrections
+      end
+
+      it 'registers an offense for defined with class method in condition' do
+        expect_offense(<<~RUBY)
+          foo = (defined? Bar.baz) ? a : b
+                ^^^^^^^^^^^^^^^^^^^^^^^^^^ Only use parentheses for ternary expressions with complex conditions.
+        RUBY
+
+        expect_no_corrections
+      end
+
+      it 'registers an offense for defined with nested constant in condition' do
+        expect_offense(<<~RUBY)
+          foo = (defined? Bar::BAZ) ? a : b
+                ^^^^^^^^^^^^^^^^^^^^^^^^^^^ Only use parentheses for ternary expressions with complex conditions.
+        RUBY
+
+        expect_no_corrections
+      end
     end
 
     context 'with an assignment condition' do