[Fix #6893] Handle implicit rescue correctly in Naming/RescuedExcepti…

…onsVariableName (#7122)

Co-authored-by: Anthony Robin <contact@anthony-robin.fr>

CHANGELOG.md

@@ -18,6 +18,7 @@
 * [#7118](https://github.com/rubocop-hq/rubocop/pull/7118): Fix `Style/WordArray` with `encoding: binary` magic comment and non-ASCII string. ([@pocke][])
 * [#7159](https://github.com/rubocop-hq/rubocop/issues/7159): Fix an error for `Lint/DuplicatedKey` when using endless range. ([@koic][])
 * [#7151](https://github.com/rubocop-hq/rubocop/issues/7151): Fix `Style/WordArray` to also consider words containing hyphens. ([@fwitzke][])
+* [#6893](https://github.com/rubocop-hq/rubocop/issues/6893): Handle implicit rescue correctly in `Naming/RescuedExceptionsVariableName`. ([@pocke][], [@anthony-robin][])
 * [#7165](https://github.com/rubocop-hq/rubocop/issues/7165): Fix an auto-correct error for `Style/ConditionalAssignment` when without `else` branch'. ([@koic][])
 
 ### Changes

lib/rubocop/ast/node/resbody_node.rb

@@ -17,12 +17,7 @@ def body
       #
       # @return [Node, nil] The exception variable of the `resbody`.
       def exception_variable
-        variable = node_parts[1]
-        return variable if variable
-
-        # When resbody is an implicit rescue (i.e. `rescue e` style),
-        # the exception variable is descendants[1].
-        descendants[1]
+        node_parts[1]
       end
     end
   end

lib/rubocop/cop/naming/rescued_exceptions_variable_name.rb

@@ -57,24 +57,20 @@ class RescuedExceptionsVariableName < Cop
         MSG = 'Use `%<preferred>s` instead of `%<bad>s`.'
 
         def on_resbody(node)
-          exception_type, @exception_name = *node
-          return unless exception_type || @exception_name
-
-          @exception_name ||= exception_type.children.first
-          return if @exception_name.const_type? ||
-                    variable_name == preferred_name
+          name = variable_name(node)
+          return unless name
+          return if preferred_name(name).to_sym == name
 
           add_offense(node, location: offense_range(node))
         end
 
         def autocorrect(node)
           lambda do |corrector|
-            offending_name = node.exception_variable.children.first
+            offending_name = variable_name(node)
+            preferred_name = preferred_name(offending_name)
             corrector.replace(offense_range(node), preferred_name)
 
-            return unless node.body
-
-            node.body.each_descendant(:lvar) do |var|
+            node.body&.each_descendant(:lvar) do |var|
               next unless var.children.first == offending_name
 
               corrector.replace(var.loc.expression, preferred_name)
@@ -89,21 +85,26 @@ def offense_range(resbody)
           variable.loc.expression
         end
 
-        def preferred_name
-          name = cop_config.fetch('PreferredName', 'e')
-          variable_name.to_s.start_with?('_') ? "_#{name}" : name
+        def preferred_name(variable_name)
+          preferred_name = cop_config.fetch('PreferredName', 'e')
+          if variable_name.to_s.start_with?('_')
+            "_#{preferred_name}"
+          else
+            preferred_name
+          end
         end
 
-        def variable_name
-          location.source
-        end
+        def variable_name(node)
+          asgn_node = node.exception_variable
+          return unless asgn_node
 
-        def location
-          @exception_name.loc.expression
+          asgn_node.children.last
         end
 
-        def message(_node = nil)
-          format(MSG, preferred: preferred_name, bad: variable_name)
+        def message(node)
+          offending_name = variable_name(node)
+          preferred_name = preferred_name(offending_name)
+          format(MSG, preferred: preferred_name, bad: offending_name)
         end
       end
     end

spec/rubocop/ast/resbody_node_spec.rb

@@ -21,7 +21,7 @@
     end
 
     context 'for an implicit rescue' do
-      let(:source) { 'begin; beginbody; rescue ex; rescuebody; end' }
+      let(:source) { 'begin; beginbody; rescue => ex; rescuebody; end' }
 
       it { expect(resbody_node.exception_variable.source).to eq('ex') }
     end

spec/rubocop/cop/naming/rescued_exceptions_variable_name_spec.rb

@@ -113,6 +113,100 @@
           RUBY
         end
       end
+
+      context 'with lower letters class name' do
+        it 'does not register an offense' do
+          expect_no_offenses(<<~RUBY)
+            begin
+              something
+            rescue my_exception
+              # do something
+            end
+          RUBY
+        end
+      end
+
+      context 'with method as `Exception`' do
+        it 'does not register an offense without variable name' do
+          expect_no_offenses(<<~RUBY)
+            begin
+              something
+            rescue ActiveSupport::JSON.my_method
+              # do something
+            end
+          RUBY
+        end
+
+        it 'does not register an offense with expected variable name' do
+          expect_no_offenses(<<~RUBY)
+            begin
+              something
+            rescue ActiveSupport::JSON.my_method => e
+              # do something
+            end
+          RUBY
+        end
+
+        it 'registers an offense with unexpected variable name' do
+          expect_offense(<<~RUBY)
+            begin
+              something
+            rescue ActiveSupport::JSON.my_method => exc
+                                                    ^^^ Use `e` instead of `exc`.
+              # do something
+            end
+          RUBY
+
+          expect_correction(<<~RUBY)
+            begin
+              something
+            rescue ActiveSupport::JSON.my_method => e
+              # do something
+            end
+          RUBY
+        end
+      end
+
+      context 'with splat operator as `Exception` list' do
+        it 'does not register an offense without variable name' do
+          expect_no_offenses(<<~RUBY)
+            begin
+              something
+            rescue *handled
+              # do something
+            end
+          RUBY
+        end
+
+        it 'does not register an offense with expected variable name' do
+          expect_no_offenses(<<~RUBY)
+            begin
+              something
+            rescue *handled => e
+              # do something
+            end
+          RUBY
+        end
+
+        it 'registers an offense with unexpected variable name' do
+          expect_offense(<<~RUBY)
+            begin
+              something
+            rescue *handled => exc
+                               ^^^ Use `e` instead of `exc`.
+              # do something
+            end
+          RUBY
+
+          expect_correction(<<~RUBY)
+            begin
+              something
+            rescue *handled => e
+              # do something
+            end
+          RUBY
+        end
+      end
     end
 
     context 'with implicit rescue' do
@@ -121,16 +215,16 @@
           expect_offense(<<~RUBY)
             begin
               something
-            rescue exc
-                   ^^^ Use `e` instead of `exc`.
+            rescue => exc
+                      ^^^ Use `e` instead of `exc`.
               # do something
             end
           RUBY
 
           expect_correction(<<~RUBY)
             begin
               something
-            rescue e
+            rescue => e
               # do something
             end
           RUBY
@@ -140,16 +234,16 @@
           expect_offense(<<~RUBY)
             begin
               something
-            rescue _exc
-                   ^^^^ Use `_e` instead of `_exc`.
+            rescue => _exc
+                      ^^^^ Use `_e` instead of `_exc`.
               # do something
             end
           RUBY
 
           expect_correction(<<~RUBY)
             begin
               something
-            rescue _e
+            rescue => _e
               # do something
             end
           RUBY
@@ -159,7 +253,7 @@
           expect_no_offenses(<<~RUBY)
             begin
               something
-            rescue e
+            rescue => e
               # do something
             end
           RUBY
@@ -169,7 +263,7 @@
           expect_no_offenses(<<~RUBY)
             begin
               something
-            rescue _e
+            rescue => _e
               # do something
             end
           RUBY