From eda5183d809a04341935b510c5af78296656938d Mon Sep 17 00:00:00 2001
From: Koichi ITO <koic.ito@gmail.com>
Date: Fri, 3 Apr 2020 14:06:31 +0900
Subject: [PATCH] [#7842] Fix a false positive for `Lint/RaiseException`

Resolve part of #7842.

This PR fixes a false positive for `Lint/RaiseException`
when raising Exception with explicit namespace.

`Exception` belonging to a namespace is expected to
inherit `StandardError`.

This PR makes `Lint/RaiseException` aware of the following differences:

```ruby
Gem::Exception.new.is_a?(StandardError) # => true
Exception.new.is_a?(StandardError)      # => false
```

On the other hand, the following case have not been resolved by this PR.

```ruby
module Gem
  def self.foo
    raise Exception
  end
end

Gem.foo #=> Gem::Exception
```

The above case will be resolved separately from this PR.
---
 CHANGELOG.md                                  | 4 ++++
 lib/rubocop/cop/lint/raise_exception.rb       | 4 ++--
 spec/rubocop/cop/lint/raise_exception_spec.rb | 7 +++++++
 3 files changed, 13 insertions(+), 2 deletions(-)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index 426ba4fcda5..7f2f31117af 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -2,6 +2,10 @@
 
 ## master (unreleased)
 
+### Bug fixes
+
+* [#7842](https://github.com/rubocop-hq/rubocop/issues/7842): Fix a false positive for `Lint/RaiseException` when raising Exception with explicit namespace. ([@koic][])
+
 ## 0.81.0 (2020-04-01)
 
 ### New features
diff --git a/lib/rubocop/cop/lint/raise_exception.rb b/lib/rubocop/cop/lint/raise_exception.rb
index fed736c57e8..e49175198d4 100644
--- a/lib/rubocop/cop/lint/raise_exception.rb
+++ b/lib/rubocop/cop/lint/raise_exception.rb
@@ -16,12 +16,12 @@ class RaiseException < Cop
         MSG = 'Use `StandardError` over `Exception`.'
 
         def_node_matcher :exception?, <<~PATTERN
-          (send nil? ${:raise :fail} (const _ :Exception) ... )
+          (send nil? ${:raise :fail} (const {cbase nil?} :Exception) ... )
         PATTERN
 
         def_node_matcher :exception_new_with_message?, <<~PATTERN
           (send nil? ${:raise :fail}
-            (send (const _ :Exception) :new ... ))
+            (send (const {cbase nil?} :Exception) :new ... ))
         PATTERN
 
         def on_send(node)
diff --git a/spec/rubocop/cop/lint/raise_exception_spec.rb b/spec/rubocop/cop/lint/raise_exception_spec.rb
index 4433e55b9d6..5e3e9a310b4 100644
--- a/spec/rubocop/cop/lint/raise_exception_spec.rb
+++ b/spec/rubocop/cop/lint/raise_exception_spec.rb
@@ -80,4 +80,11 @@
   it 'does not register an offense for `fail` without arguments' do
     expect_no_offenses('fail')
   end
+
+  it 'does not register an offense when raising Exception with explicit ' \
+     'namespace' do
+    expect_no_offenses(<<~RUBY)
+      raise Foo::Exception
+    RUBY
+  end
 end