[Fix rubocop#10963] Fix a false positive for Layout/IndentationWidth

Fixes rubocop#10963. This PR fixes a false positive for `Layout/IndentationWidth` when using aligned empty `else` in pattern matching.
koic · Aug 25, 2022 · 10cf610 · 10cf610
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diff --git a/changelog/fix_a_false_positive_for_layout_indentation_width.md b/changelog/fix_a_false_positive_for_layout_indentation_width.md
@@ -0,0 +1 @@
+* [#10963](https://github.com/rubocop/rubocop/issues/10963): Fix a false positive for `Layout/IndentationWidth` when using aligned empty `else` in pattern matching. ([@koic][])
diff --git a/lib/rubocop/cop/layout/indentation_width.rb b/lib/rubocop/cop/layout/indentation_width.rb
@@ -148,7 +148,9 @@ def on_case_match(case_match)
             check_indentation(in_pattern_node.loc.keyword, in_pattern_node.body)
           end
 
-          check_indentation(case_match.in_pattern_branches.last.loc.keyword, case_match.else_branch)
+          else_branch = case_match.else_branch&.empty_else_type? ? nil : case_match.else_branch
+
+          check_indentation(case_match.in_pattern_branches.last.loc.keyword, else_branch)
         end
 
         def on_if(node, base = node)

diff --git a/spec/rubocop/cop/layout/indentation_width_spec.rb b/spec/rubocop/cop/layout/indentation_width_spec.rb
@@ -915,6 +915,16 @@ def x
         RUBY
       end
 
+      it 'accepts aligned value in `in` clause and `else` is empty' do
+        expect_no_offenses(<<~'RUBY')
+          case x
+          in 42
+            foo
+          else
+          end
+        RUBY
+      end
+
       it 'accepts case/in/else laid out as a table' do
         expect_no_offenses(<<~RUBY)
           case sexp.loc.keyword.source