From 73b3180ae960d3859d46dad3b1a1b2d768631bf8 Mon Sep 17 00:00:00 2001
From: Koichi ITO <koic.ito@gmail.com>
Date: Sun, 6 Sep 2020 04:00:16 +0900
Subject: [PATCH] Fix a false positive for `Rails/DynamicFindBy`

This PR fixes a false positive for `Rails/DynamicFindBy`
when any of the arguments are splat argument.

```console
% cat example.rb
find_by_scan(*args)

% bundle exec rubocop -a example.rb
(snip)

Inspecting 1 file
E

Offenses:

example.rb:1:1: C: [Corrected] Rails/DynamicFindBy: Use find_by instead
of dynamic find_by_scan.
find_by_scan(*args)
^^^^^^^^^^^^^^^^^^^
example.rb:1:15: E: Lint/Syntax: unexpected token tSTAR
(Using Ruby 2.7 parser; configure using TargetRubyVersion parameter,
under AllCops)
find_by(scan: *args)
              ^

1 file inspected, 2 offenses detected, 1 offense corrected

% cat example.rb
find_by(scan: *args)

% ruby -c example.rb
example.rb:1: syntax error, unexpected *
find_by(scan: *args)
```
---
 CHANGELOG.md                                   | 1 +
 lib/rubocop/cop/rails/dynamic_find_by.rb       | 1 +
 spec/rubocop/cop/rails/dynamic_find_by_spec.rb | 8 ++++++++
 3 files changed, 10 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index ee41ba5e9b..6e036e8717 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -9,6 +9,7 @@
 * [#338](https://github.com/rubocop-hq/rubocop-rails/issues/338): Fix a false positive for `Rails/IndexBy` and `Rails/IndexWith` when the `each_with_object` hash is used in the transformed key or value. ([@eugeneius][])
 * [#351](https://github.com/rubocop-hq/rubocop-rails/pull/351): Add `<>` operator to `Rails/WhereNot` cop. ([@Tietew][])
 * [#352](https://github.com/rubocop-hq/rubocop-rails/pull/352): Do not register offense if given a splatted hash. ([@dvandersluis][])
+* [#346](https://github.com/rubocop-hq/rubocop-rails/pull/346): Fix a false positive for `Rails/DynamicFindBy` when any of the arguments are splat argument. ([@koic][])
 
 ## 2.8.0 (2020-09-04)
 
diff --git a/lib/rubocop/cop/rails/dynamic_find_by.rb b/lib/rubocop/cop/rails/dynamic_find_by.rb
index 3c2e349b59..e86efd6d26 100644
--- a/lib/rubocop/cop/rails/dynamic_find_by.rb
+++ b/lib/rubocop/cop/rails/dynamic_find_by.rb
@@ -41,6 +41,7 @@ def on_send(node)
           method_name = node.method_name
           static_name = static_method_name(method_name)
           return unless static_name
+          return if node.arguments.any?(&:splat_type?)
 
           add_offense(node,
                       message: format(MSG, static_name: static_name,
diff --git a/spec/rubocop/cop/rails/dynamic_find_by_spec.rb b/spec/rubocop/cop/rails/dynamic_find_by_spec.rb
index 7866a49dad..d5655dc582 100644
--- a/spec/rubocop/cop/rails/dynamic_find_by_spec.rb
+++ b/spec/rubocop/cop/rails/dynamic_find_by_spec.rb
@@ -133,6 +133,14 @@
     expect_no_offenses('User.find_by(name: name)')
   end
 
+  it 'accepts splat argument' do
+    expect_no_offenses('User.find_by_scan(*args)')
+  end
+
+  it 'accepts any of the arguments are splat argument' do
+    expect_no_offenses('User.find_by_foo_and_bar(arg, *args)')
+  end
+
   it 'accepts method in whitelist' do
     expect_no_offenses(<<~RUBY)
       User.find_by_sql(["select * from users where name = ?", name])