From 3b0552b9989db97104cfe0fc30515e9b6ae549f2 Mon Sep 17 00:00:00 2001
From: Koichi ITO <koic.ito@gmail.com>
Date: Tue, 9 Jun 2020 16:22:46 +0900
Subject: [PATCH] [Fix #8124] Fix a false positive for
 `Lint/FormatParameterMismatch`

Fixes #8124.

This PR fixes a false positive for `Lint/FormatParameterMismatch`
using named parameters with escaped `%`.
---
 CHANGELOG.md                                            | 1 +
 lib/rubocop/cop/utils/format_string.rb                  | 2 +-
 spec/rubocop/cop/lint/format_parameter_mismatch_spec.rb | 4 ++++
 spec/rubocop/cop/utils/format_string_spec.rb            | 5 +++++
 4 files changed, 11 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index fa4388f1a63..facf7914145 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -10,6 +10,7 @@
 ### Bug fixes
 
 * [#8115](https://github.com/rubocop-hq/rubocop/issues/8115): Fix false negative for `Lint::FormatParameterMismatch` when argument contains formatting. ([@andrykonchin][])
+* [#8124](https://github.com/rubocop-hq/rubocop/issues/8124): Fix a false positive for `Lint/FormatParameterMismatch` when using named parameters with escaped `%`. ([@koic][])
 
 ## 0.85.1 (2020-06-07)
 
diff --git a/lib/rubocop/cop/utils/format_string.rb b/lib/rubocop/cop/utils/format_string.rb
index 383d9e72ddc..dd99d5e27e0 100644
--- a/lib/rubocop/cop/utils/format_string.rb
+++ b/lib/rubocop/cop/utils/format_string.rb
@@ -120,7 +120,7 @@ def parse
         end
 
         def mixed_formats?
-          formats = format_sequences.map do |seq|
+          formats = format_sequences.reject(&:percent?).map do |seq|
             if seq.name
               :named
             elsif seq.max_digit_dollar_num
diff --git a/spec/rubocop/cop/lint/format_parameter_mismatch_spec.rb b/spec/rubocop/cop/lint/format_parameter_mismatch_spec.rb
index ffbb82cb7d4..1bd7d642218 100644
--- a/spec/rubocop/cop/lint/format_parameter_mismatch_spec.rb
+++ b/spec/rubocop/cop/lint/format_parameter_mismatch_spec.rb
@@ -222,6 +222,10 @@
     expect_no_offenses('"foo %{bar} baz" % { bar: 42 }')
   end
 
+  it 'does not register an offense when using named parameters with escaped `%`' do
+    expect_no_offenses('format("%%%<hex>02X", hex: 10)')
+  end
+
   it 'identifies correctly digits for spacing in format' do
     expect_no_offenses('"duration: %10.fms" % 42')
   end
diff --git a/spec/rubocop/cop/utils/format_string_spec.rb b/spec/rubocop/cop/utils/format_string_spec.rb
index 269f92f50bf..6fbaa787642 100644
--- a/spec/rubocop/cop/utils/format_string_spec.rb
+++ b/spec/rubocop/cop/utils/format_string_spec.rb
@@ -97,6 +97,11 @@ def format_sequences(string)
       expect(fs.valid?).to eq true
     end
 
+    it 'returns true when there are only named with escaped `%` formats' do
+      fs = described_class.new('%%%{foo}d')
+      expect(fs.valid?).to eq true
+    end
+
     it 'returns false when there are unnumbered and numbered formats' do
       fs = described_class.new('%s %1$d')
       expect(fs.valid?).to eq false