From 9fe7006c9dff0b250618dff52c62b98a52f0c2ac Mon Sep 17 00:00:00 2001
From: Andrew Konchin <andry.konchin@gmail.com>
Date: Mon, 8 Jun 2020 10:44:11 +0300
Subject: [PATCH] Fix #8115. Lint/FormatParameterMismatch. Fix bug with
 formatting in argument

---
 CHANGELOG.md                                            | 4 ++++
 lib/rubocop/cop/lint/format_parameter_mismatch.rb       | 7 ++++++-
 spec/rubocop/cop/lint/format_parameter_mismatch_spec.rb | 8 ++++++++
 3 files changed, 18 insertions(+), 1 deletion(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 5405090a33e..fa4388f1a63 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -7,6 +7,10 @@
 * [#8111](https://github.com/rubocop-hq/rubocop/pull/8111): Add auto-correct for `Style/StructInheritance`. ([@tejasbubane][])
 * [#8113](https://github.com/rubocop-hq/rubocop/pull/8113): Let `expect_offense` templates add variable-length whitespace with `_{foo}`. ([@eugeneius][])
 
+### Bug fixes
+
+* [#8115](https://github.com/rubocop-hq/rubocop/issues/8115): Fix false negative for `Lint::FormatParameterMismatch` when argument contains formatting. ([@andrykonchin][])
+
 ## 0.85.1 (2020-06-07)
 
 ### Bug fixes
diff --git a/lib/rubocop/cop/lint/format_parameter_mismatch.rb b/lib/rubocop/cop/lint/format_parameter_mismatch.rb
index e5cf62c0ada..356b06d5175 100644
--- a/lib/rubocop/cop/lint/format_parameter_mismatch.rb
+++ b/lib/rubocop/cop/lint/format_parameter_mismatch.rb
@@ -65,7 +65,12 @@ def format_string?(node)
         end
 
         def invalid_format_string?(node)
-          !RuboCop::Cop::Utils::FormatString.new(node.source).valid?
+          string = if sprintf?(node) || format?(node)
+                     node.first_argument.source
+                   else
+                     node.receiver.source
+                   end
+          !RuboCop::Cop::Utils::FormatString.new(string).valid?
         end
 
         def offending_node?(node)
diff --git a/spec/rubocop/cop/lint/format_parameter_mismatch_spec.rb b/spec/rubocop/cop/lint/format_parameter_mismatch_spec.rb
index c0d9601f837..ffbb82cb7d4 100644
--- a/spec/rubocop/cop/lint/format_parameter_mismatch_spec.rb
+++ b/spec/rubocop/cop/lint/format_parameter_mismatch_spec.rb
@@ -187,6 +187,14 @@
     end
   end
 
+  # Regression: https://github.com/rubocop-hq/rubocop/issues/8115
+  context 'when argument itself contains format characters and ' \
+          'formats in format string and argument are not equal' do
+    it 'ignores argument formatting' do
+      expect_no_offenses(%{format('%<t>s', t: '%d')})
+    end
+  end
+
   it 'ignores percent right next to format string' do
     expect_no_offenses('format("%0.1f%% percent", 22.5)')
   end