Fix a false positive for Lint/FormatParameterMismatch when format string is only interpolated string

changelog/fix_a_false_positive_for_lint_format_paramater_mismatch.md

@@ -0,0 +1 @@
+* [#11487](https://github.com/rubocop/rubocop/pull/11487): Fix a false positive for `Lint/FormatParameterMismatch` when format string is only interpolated string. ([@ydah][])

lib/rubocop/cop/lint/format_parameter_mismatch.rb

@@ -80,6 +80,7 @@ def offending_node?(node)
           num_of_format_args, num_of_expected_fields = count_matches(node)
 
           return false if num_of_format_args == :unknown
+          return false if num_of_expected_fields.zero? && node.child_nodes.first.dstr_type?
 
           matched_arguments_count?(num_of_expected_fields, num_of_format_args)
         end

spec/rubocop/cop/lint/format_parameter_mismatch_spec.rb

@@ -51,6 +51,13 @@
     RUBY
   end
 
+  it 'registers an offense when there are no expected format string' do
+    expect_offense(<<~RUBY)
+      format("something", 1)
+      ^^^^^^ Number of arguments (1) to `format` doesn't match the number of fields (0).
+    RUBY
+  end
+
   it 'registers an offense when there are more arguments than expected' do
     expect_offense(<<~RUBY)
       format("%s %s", 1, 2, 3)
@@ -314,6 +321,10 @@
       expect_no_offenses('format("#{foo} %s", "bar")')
     end
 
+    it 'does not register an offense when only interpolated string' do
+      expect_no_offenses('format("#{foo}", "bar", "baz")')
+    end
+
     it 'registers an offense for String#% when the fields do not match' do
       expect_offense(<<~'RUBY')
         "%s %s" % ["#{foo}", 1, 2]
@@ -324,6 +335,10 @@
     it 'does not register an offense for String#% when the fields match' do
       expect_no_offenses('"%s %s" % ["#{foo}", 1]')
     end
+
+    it 'does not register an offense for String#% when only interpolated string' do
+      expect_no_offenses('"#{foo}" % [1, 2]')
+    end
   end
 
   context 'with interpolated string in argument' do