Cop for checking empty raise

Gemfile

@@ -0,0 +1,5 @@
+source 'https://rubygems.org'
+
+gem "rspec", "~> 3.8.0"
+gem "rubocop"
+gem "rubocop-rspec"

Gemfile.lock

@@ -0,0 +1,52 @@
+GEM
+  remote: https://rubygems.org/
+  specs:
+    ast (2.4.2)
+    diff-lcs (1.5.0)
+    json (2.6.2)
+    parallel (1.22.1)
+    parser (3.1.2.0)
+      ast (~> 2.4.1)
+    rainbow (3.1.1)
+    regexp_parser (2.5.0)
+    rexml (3.2.5)
+    rspec (3.8.0)
+      rspec-core (~> 3.8.0)
+      rspec-expectations (~> 3.8.0)
+      rspec-mocks (~> 3.8.0)
+    rspec-core (3.8.2)
+      rspec-support (~> 3.8.0)
+    rspec-expectations (3.8.6)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.8.0)
+    rspec-mocks (3.8.2)
+      diff-lcs (>= 1.2.0, < 2.0)
+      rspec-support (~> 3.8.0)
+    rspec-support (3.8.3)
+    rubocop (1.32.0)
+      json (~> 2.3)
+      parallel (~> 1.10)
+      parser (>= 3.1.0.0)
+      rainbow (>= 2.2.2, < 4.0)
+      regexp_parser (>= 1.8, < 3.0)
+      rexml (>= 3.2.5, < 4.0)
+      rubocop-ast (>= 1.19.1, < 2.0)
+      ruby-progressbar (~> 1.7)
+      unicode-display_width (>= 1.4.0, < 3.0)
+    rubocop-ast (1.19.1)
+      parser (>= 3.1.1.0)
+    rubocop-rspec (2.12.1)
+      rubocop (~> 1.31)
+    ruby-progressbar (1.11.0)
+    unicode-display_width (2.2.0)
+
+PLATFORMS
+  x86_64-linux
+
+DEPENDENCIES
+  rspec (~> 3.8.0)
+  rubocop
+  rubocop-rspec
+
+BUNDLED WITH
+   2.3.7

lib/cops/raise_message_cop.rb

@@ -0,0 +1,22 @@
+# frozen_string_literal: true
+
+# This cop checks if there is any "raise" code without a message
+# Examples:
+# Good -> raise "Message"
+# Good -> 
+module RuboCop
+    module Cop
+      module CustomCops
+        class RaiseMessageCop < Base
+          def on_send(node)
+            return unless node.command?(:raise)
+            # If the raise encountered does not have any arguments, add the offense
+            # It ensures that raise is always accompanied with an argument.
+            if node.arguments.size<1
+              add_offense(node, message: "Raise should be accompanied by a message/argument.")
+            end
+          end
+        end
+      end
+  end
+end

lib/cops/readme.md

@@ -14,6 +14,23 @@ PutLoggerFormatCop ensures that the message format received on encountering **pu
 ~~~ruby
 "<module/class>#method_name:<space><message>". 
 ~~~
+
+~~~ ruby
+# not allowed.
+puts("Message here")
+~~~
+
+~~~ruby
+# allowed, if both class/module name and method name are available.
+puts("moduleS#method2: Message here")
+~~~
+
+~~~ruby
+# allowed, if only method_name is available.
+puts("methodS: Message here")
+~~~
+Disabled by default
+
 Enabling the cop inside .rubocop.yml :
 ~~~ruby
 CustomCop/PutLoggerFormatCop:
@@ -57,3 +74,32 @@ to disable it add the following lines in .rubocop.yml of your repo:
 CustomCop/DuplicateConstantCop:
   Enabled: false
 ~~~
+
+### RaiseMessageCop
+RaiseMessageCop ensures that there is no empty occurence of raise, i.e it makes sure that "raise" is always accompanied by an argument/message.
+
+### Reason to add this cop
+if we have an occurence of raise without a message or an argument it breaks the flow of the code and the rest of the code becomes unreachable, hence raising "unreachable code" offense on rubocop.
+
+~~~ ruby
+# not allowed, raise without a message or argument.
+raise
+~~~
+
+~~~ ruby
+# allowed
+raise "Error message
+~~~
+
+~~~ ruby
+# allowed
+raise StandardError, 'message'
+~~~
+
+Enabled by default
+
+to disable it add the following lines in .rubocop.yml of your repo:
+~~~ruby
+CustomCop/RaiseMessageCop:
+  Enabled: false
+~~~

rubocop.yml

@@ -10,8 +10,12 @@ AllCops:
 require:
   - './lib/cops/logger_format_cop.rb'
   - './lib/cops/duplicate_constant_cop.rb'
+  - './lib/cops/raise_message_cop.rb'
   - 'rubocop-rails'
-
+
+CustomCops/RaiseMessageCop:
+  Enabled: true
+
 CustomCops/PutLoggerFormatCop:
   Enabled: false
 

spec/raise_message_cop_spec.rb

@@ -0,0 +1,66 @@
+require 'spec_helper'
+require_relative '../lib/cops/raise_message_cop.rb'
+RSpec.describe RuboCop::Cop::CustomCops::RaiseMessageCop do
+    context 'corrector' do
+        subject(:cop) { described_class.new }
+        it 'it should register an offense if there is an empty raise present' do
+            expect_offense(<<~RUBY)
+              module D
+                class A
+                    def B
+                      raise
+                      ^^^^^ Raise should be accompanied by a message/argument.
+                    end
+                end
+              end
+            RUBY
+        end
+        it 'it should not register an offense if raise is accompanied by an argument/message' do
+          expect_no_offenses (<<~RUBY)
+          module D
+            class A
+                def B
+                  raise "A message with context to the raised error."
+                end
+            end
+          end
+
+          RUBY
+
+          expect_no_offenses (<<~RUBY)
+          module D
+            class A
+                def B
+                  raise StandardError, 'message'
+                end
+            end
+          end
+
+          RUBY
+        end
+        it 'it should register an offense for an inline condtion' do
+          expect_offense(<<~RUBY)
+          module D
+            class A
+                def B
+                  raise unless status
+                  ^^^^^ Raise should be accompanied by a message/argument.
+                end
+            end
+          end
+
+          RUBY
+
+          expect_no_offenses (<<~RUBY)
+          module D
+            class A
+                def B
+                  raise StandardError, 'message' unless status
+                end
+            end
+          end
+
+          RUBY
+        end
+    end
+end

spec/spec_helper.rb

@@ -0,0 +1,7 @@
+require 'rubocop'
+require 'rubocop/rspec/support'
+require 'rspec'
+
+RSpec.configure do |config|
+  config.include RuboCop::RSpec::ExpectOffense
+end