[Fix #7130] Skip autocorrect in Style/FormatString if second argume…

…nt is variable

For `String#%` is second argument is variable, flag offense but skip
autocorrect. It is not possible for rubocop to know if variable is
array in which case the autocorrect leads to invalid code.

Closes #7130.

CHANGELOG.md

@@ -21,6 +21,8 @@
 * [#6893](https://github.com/rubocop-hq/rubocop/issues/6893): Handle implicit rescue correctly in `Naming/RescuedExceptionsVariableName`. ([@pocke][], [@anthony-robin][])
 * [#7165](https://github.com/rubocop-hq/rubocop/issues/7165): Fix an auto-correct error for `Style/ConditionalAssignment` when without `else` branch'. ([@koic][])
 * [#7171](https://github.com/rubocop-hq/rubocop/issues/7171): Fix an error for `Style/SafeNavigation` when using `unless nil?` as a safeguarded'. ([@koic][])
+* [#7113](https://github.com/rubocop-hq/rubocop/pull/7113): This PR renames `EnforcedStyle: rails` to `EnabledStyle: outdented_access_modifiers` for `Layout/IndentationConsistency`. ([@koic][])
+* [#7130](https://github.com/rubocop-hq/rubocop/pull/7130): Skip autocorrect in `Style/FormatString` if second argument to `String#%` is a variable. ([@tejasbubane][])
 
 ### Changes
 

lib/rubocop/cop/style/format_string.rb

@@ -48,6 +48,10 @@ class FormatString < Cop
         }
         PATTERN
 
+        def_node_matcher :variable_argument?, <<-PATTERN
+          (send {str dstr} :% {send_type? lvar_type?})
+        PATTERN
+
         def on_send(node)
           formatter(node) do |selector|
             detected_style = selector == :% ? :percent : selector
@@ -70,10 +74,10 @@ def method_name(style_name)
         end
 
         def autocorrect(node)
-          lambda do |corrector|
-            detected_method = node.method_name
+          return if variable_argument?(node)
 
-            case detected_method
+          lambda do |corrector|
+            case node.method_name
             when :%
               autocorrect_from_percent(corrector, node)
             when :format, :sprintf

spec/rubocop/cop/style/format_string_spec.rb

@@ -20,6 +20,13 @@
       RUBY
     end
 
+    it 'registers an offense for variable argument' do
+      expect_offense(<<~RUBY)
+        puts "%f" % a
+                  ^ Favor `sprintf` over `String#%`.
+      RUBY
+    end
+
     it 'does not register an offense for numbers' do
       expect_no_offenses('puts 10 % 4')
     end
@@ -68,6 +75,21 @@
       corrected = autocorrect_source('puts x % { a: 10, b: 11 }')
       expect(corrected).to eq 'puts sprintf(x, a: 10, b: 11)'
     end
+
+    it 'does not auto-correct String#% with variable argument' do
+      source = <<~RUBY
+        puts "%d" % a
+      RUBY
+      expect(autocorrect_source(source)).to eq(source)
+    end
+
+    it 'does not auto-correct String#% with variable argument and assignment' do
+      source = <<~RUBY
+        a = something()
+        puts "%d" % a
+      RUBY
+      expect(autocorrect_source(source)).to eq(source)
+    end
   end
 
   context 'when enforced style is format' do
@@ -94,6 +116,13 @@
       RUBY
     end
 
+    it 'registers an offense for variable argument' do
+      expect_offense(<<~RUBY)
+        puts "%f" % a
+                  ^ Favor `format` over `String#%`.
+      RUBY
+    end
+
     it 'does not register an offense for numbers' do
       expect_no_offenses('puts 10 % 4')
     end
@@ -142,6 +171,21 @@
       corrected = autocorrect_source('puts x % { a: 10, b: 11 }')
       expect(corrected).to eq 'puts format(x, a: 10, b: 11)'
     end
+
+    it 'does not auto-correct String#% with variable argument' do
+      source = <<~RUBY
+        puts "%d" % a
+      RUBY
+      expect(autocorrect_source(source)).to eq(source)
+    end
+
+    it 'does not auto-correct String#% with variable argument and assignment' do
+      source = <<~RUBY
+        a = something()
+        puts "%d" % a
+      RUBY
+      expect(autocorrect_source(source)).to eq(source)
+    end
   end
 
   context 'when enforced style is percent' do