[Fix #8281] Improve WhileUntilModifier detection and correction

* Detect inline cases (while foo; bar; end)
* Preserve comments when auto-correcting
* Handle RHS usage in assignments

changelog/fix_while_until_modifier_autocorrection.md

@@ -0,0 +1 @@
+* [#8281](https://github.com/rubocop-hq/rubocop/issues/8281): Fix Style/WhileUntilModifier handling comments and assignment when correcting to modifier form. ([@Darhazer][])

lib/rubocop/cop/style/while_until_modifier.rb

@@ -41,12 +41,10 @@ class WhileUntilModifier < Base
               'having a single-line body.'
 
         def on_while(node)
-          return unless node.multiline? && single_line_as_modifier?(node)
+          return unless single_line_as_modifier?(node)
 
           add_offense(node.loc.keyword, message: format(MSG, keyword: node.keyword)) do |corrector|
-            oneline = "#{node.body.source} #{node.keyword} #{node.condition.source}"
-
-            corrector.replace(node, oneline)
+            corrector.replace(node, to_modifier_form(node))
           end
         end
         alias on_until on_while

spec/rubocop/cop/style/if_unless_modifier_spec.rb

@@ -357,71 +357,6 @@ def f
     RUBY
   end
 
-  it "doesn't break if-end when used as RHS of local var assignment" do
-    expect_offense(<<~RUBY)
-      a = if b
-          ^^ Favor modifier `if` usage when having a single-line body. [...]
-        1
-      end
-    RUBY
-
-    expect_correction(<<~RUBY)
-      a = (1 if b)
-    RUBY
-  end
-
-  it "doesn't break if-end when used as RHS of instance var assignment" do
-    expect_offense(<<~RUBY)
-      @a = if b
-           ^^ Favor modifier `if` usage when having a single-line body. [...]
-        1
-      end
-    RUBY
-
-    expect_correction(<<~RUBY)
-      @a = (1 if b)
-    RUBY
-  end
-
-  it "doesn't break if-end when used as RHS of class var assignment" do
-    expect_offense(<<~RUBY)
-      @@a = if b
-            ^^ Favor modifier `if` usage when having a single-line body. [...]
-        1
-      end
-    RUBY
-
-    expect_correction(<<~RUBY)
-      @@a = (1 if b)
-    RUBY
-  end
-
-  it "doesn't break if-end when used as RHS of constant assignment" do
-    expect_offense(<<~RUBY)
-      A = if b
-          ^^ Favor modifier `if` usage when having a single-line body. [...]
-        1
-      end
-    RUBY
-
-    expect_correction(<<~RUBY)
-      A = (1 if b)
-    RUBY
-  end
-
-  it "doesn't break if-end when used as RHS of binary arithmetic" do
-    expect_offense(<<~RUBY)
-      a + if b
-          ^^ Favor modifier `if` usage when having a single-line body. [...]
-        1
-      end
-    RUBY
-
-    expect_correction(<<~RUBY)
-      a + (1 if b)
-    RUBY
-  end
-
   it 'adds parens in autocorrect when if-end used with `||` operator' do
     expect_offense(<<~RUBY)
       a || if b

spec/support/condition_modifier_cop.rb

@@ -80,6 +80,95 @@
       RUBY
     end
 
+    it "doesn't break when used as RHS of local var assignment" do
+      expect_offense(<<~RUBY, keyword: keyword)
+        a = %{keyword} b
+            ^{keyword} Favor modifier `%{keyword}` usage when having a single-line body.#{extra_message}
+          1
+        end
+      RUBY
+
+      expect_correction(<<~RUBY)
+        a = (1 #{keyword} b)
+      RUBY
+    end
+
+    it "doesn't break when used as RHS of instance var assignment" do
+      expect_offense(<<~RUBY, keyword: keyword)
+        @a = %{keyword} b
+             ^{keyword} Favor modifier `%{keyword}` usage when having a single-line body.#{extra_message}
+          1
+        end
+      RUBY
+
+      expect_correction(<<~RUBY)
+        @a = (1 #{keyword} b)
+      RUBY
+    end
+
+    it "doesn't break when used as RHS of class var assignment" do
+      expect_offense(<<~RUBY, keyword: keyword)
+        @@a = %{keyword} b
+              ^{keyword} Favor modifier `%{keyword}` usage when having a single-line body.#{extra_message}
+          1
+        end
+      RUBY
+
+      expect_correction(<<~RUBY)
+        @@a = (1 #{keyword} b)
+      RUBY
+    end
+
+    it "doesn't break when used as RHS of constant assignment" do
+      expect_offense(<<~RUBY, keyword: keyword)
+        A = %{keyword} b
+            ^{keyword} Favor modifier `%{keyword}` usage when having a single-line body.#{extra_message}
+          1
+        end
+      RUBY
+
+      expect_correction(<<~RUBY)
+        A = (1 #{keyword} b)
+      RUBY
+    end
+
+    it "doesn't break when used as RHS of binary arithmetic" do
+      expect_offense(<<~RUBY, keyword: keyword)
+        a + %{keyword} b
+            ^{keyword} Favor modifier `%{keyword}` usage when having a single-line body.#{extra_message}
+          1
+        end
+      RUBY
+
+      expect_correction(<<~RUBY)
+        a + (1 #{keyword} b)
+      RUBY
+    end
+
+    it 'handles inline comments during autocorrection' do
+      expect_offense(<<~RUBY, keyword: keyword)
+        %{keyword} bar # important comment not to be nuked
+        ^{keyword} Favor modifier `%{keyword}` usage when having a single-line body.#{extra_message}
+          baz
+        end
+      RUBY
+
+      expect_correction(<<~RUBY)
+        baz #{keyword} bar # important comment not to be nuked
+      RUBY
+    end
+
+    it 'handles one-line usage' do
+      expect_offense(<<~RUBY, keyword: keyword)
+        %{keyword} foo; bar; end
+        ^{keyword} Favor modifier `%{keyword}` usage when having a single-line body.#{extra_message}
+      RUBY
+
+      expect_correction(<<~RUBY)
+        bar #{keyword} foo
+      RUBY
+    end
+
     # See: https://github.com/rubocop-hq/rubocop/issues/8273
     context 'accepts multiline condition in modifier form' do
       it 'registers an offense' do