[Fix #6701] Trailing comma detection regression with HEREDOC

The TrailingCommaInArguments and TrailingCommaInArrayLiteral cops
have a false positive when the parent node contains HEREDOC with
commas in them. The issue appears to be due to lax comma detection.

Instead of only matching the last item for heredoc, match all items
and search for trailing commas, excluding newlines in match when
heredoc is present

CHANGELOG.md

@@ -17,6 +17,7 @@
 * [#6382](https://github.com/rubocop-hq/rubocop/issues/6382): Fix `Layout/IndentationWidth` with `Layout/EndAlignment` set to start_of_line. ([@dischorde][], [@siegfault][], [@mhelmetag][])
 * [#6710](https://github.com/rubocop-hq/rubocop/issues/6710): Fix `Naming/MemoizedInstanceVariableName` on method starts with underscore. ([@pocke][])
 * [#6722](https://github.com/rubocop-hq/rubocop/issues/6722): Fix an error for `Style/OneLineConditional` when `then` branch has no body. ([@koic][])
+* [#6702](https://github.com/rubocop-hq/rubocop/pull/6702): Fix `TrailingComma` regression where heredoc with commas caused false positives. ([@abrom][])
 
 ### Changes
 

lib/rubocop/cop/mixin/trailing_comma.rb

@@ -17,11 +17,13 @@ def style_parameter_name
       end
 
       def check(node, items, kind, begin_pos, end_pos)
-        return if heredoc?(items.last)
-
         after_last_item = range_between(begin_pos, end_pos)
 
-        comma_offset = after_last_item.source =~ /,/
+        # If there is any heredoc in items, then match the comma succeeding
+        # any whitespace (except newlines), otherwise allow for newlines
+        comma_regex = any_heredoc?(items) ? /\A[^\S\n]*,/ : /\A\s*,/
+        comma_offset = after_last_item.source =~ comma_regex &&
+                       after_last_item.source.index(',')
 
         if comma_offset && !inside_comment?(after_last_item, comma_offset)
           check_comma(node, kind, after_last_item.begin_pos + comma_offset)
@@ -167,6 +169,10 @@ def avoid_autocorrect?(_nodes)
         false
       end
 
+      def any_heredoc?(items)
+        items.any? { |item| heredoc?(item) }
+      end
+
       def heredoc?(node)
         return false unless node.is_a?(RuboCop::AST::Node)
         return true if node.loc.respond_to?(:heredoc_body)

spec/rubocop/cop/style/trailing_comma_in_arguments_spec.rb

@@ -11,6 +11,14 @@
       RUBY
     end
 
+    it 'registers an offense for trailing comma preceded by whitespace' \
+       ' in a method call' do
+      expect_offense(<<-RUBY.strip_indent)
+        some_method(a, b, c , )
+                            ^ Avoid comma after the last parameter of a method call#{extra_info}.
+      RUBY
+    end
+
     it 'registers an offense for trailing comma in a method call with hash' \
        ' parameters at the end' do
       expect_offense(<<-RUBY.strip_indent)
@@ -57,6 +65,14 @@
       new_source = autocorrect_source('some_method(a, b, c: 0, d: 1, )')
       expect(new_source).to eq('some_method(a, b, c: 0, d: 1 )')
     end
+
+    it 'accepts heredoc without trailing comma' do
+      expect_no_offenses(<<-RUBY.strip_indent)
+        route(1, <<-HELP.chomp)
+        ...
+        HELP
+      RUBY
+    end
   end
 
   context 'with single line list of values' do
@@ -167,6 +183,33 @@
         RUBY
       end
 
+      it 'accepts comma inside a modified heredoc parameter' do
+        expect_no_offenses(<<-RUBY.strip_indent)
+          some_method(
+            <<-LOREM.delete("\\n")
+              Something with a , in it
+            LOREM
+          )
+        RUBY
+      end
+
+      it 'auto-corrects unwanted comma after modified heredoc parameter' do
+        new_source = autocorrect_source(<<-RUBY.strip_indent)
+          some_method(
+            <<-LOREM.delete("\\n"),
+              Something with a , in it
+            LOREM
+          )
+        RUBY
+        expect(new_source).to eq(<<-RUBY.strip_indent)
+          some_method(
+            <<-LOREM.delete("\\n")
+              Something with a , in it
+            LOREM
+          )
+        RUBY
+      end
+
       context 'when there is string interpolation inside heredoc parameter' do
         it 'accepts comma inside a heredoc parameter' do
           expect_no_offenses(<<-RUBY.strip_indent)
@@ -280,7 +323,7 @@
       it 'accepts missing comma after heredoc with comments' do
         expect_no_offenses(<<-RUBY.strip_indent)
           route(
-            <<-HELP.chomp
+            a, <<-HELP.chomp
             ,
             # some comment
             HELP
@@ -437,15 +480,19 @@
         RUBY
       end
 
-      it 'accepts missing comma after a heredoc' do
-        # A heredoc that's the last item in a literal or parameter list can not
-        # have a trailing comma. It's a syntax error.
-        expect_no_offenses(<<-RUBY.strip_indent)
+      it 'auto-corrects missing comma after a heredoc' do
+        new_source = autocorrect_source(<<-RUBY.strip_indent)
           route(1, <<-HELP.chomp
           ...
           HELP
           )
         RUBY
+        expect(new_source).to eq(<<-RUBY.strip_indent)
+          route(1, <<-HELP.chomp,
+          ...
+          HELP
+          )
+        RUBY
       end
 
       it 'auto-corrects missing comma in a method call with hash parameters' \

spec/rubocop/cop/style/trailing_comma_in_array_literal_spec.rb

@@ -100,6 +100,33 @@
                    ]
         RUBY
       end
+
+      it 'accepts HEREDOC with commas' do
+        expect_no_offenses(<<-RUBY.strip_indent)
+          [
+            <<-TEXT, 123
+              Something with a , in it
+            TEXT
+          ]
+        RUBY
+      end
+
+      it 'auto-corrects unwanted comma where HEREDOC has commas' do
+        new_source = autocorrect_source(<<-RUBY.strip_indent)
+          [
+            <<-TEXT, 123,
+              Something with a , in it
+            TEXT
+          ]
+        RUBY
+        expect(new_source).to eq(<<-RUBY.strip_indent)
+          [
+            <<-TEXT, 123
+              Something with a , in it
+            TEXT
+          ]
+        RUBY
+      end
     end
 
     context 'when EnforcedStyleForMultiline is comma' do

spec/rubocop/cop/style/trailing_comma_in_hash_literal_spec.rb

@@ -154,12 +154,10 @@
         RUBY
       end
 
-      it 'accepts missing comma after a heredoc' do
-        # A heredoc that's the last item in a literal or parameter list can not
-        # have a trailing comma. It's a syntax error.
+      it 'accepts trailing comma after a heredoc' do
         expect_no_offenses(<<-RUBY.strip_indent)
           route(help: {
-            'auth' => <<-HELP.chomp
+            'auth' => <<-HELP.chomp,
           ...
           HELP
           })
@@ -238,12 +236,10 @@
         RUBY
       end
 
-      it 'accepts missing comma after a heredoc' do
-        # A heredoc that's the last item in a literal or parameter list can not
-        # have a trailing comma. It's a syntax error.
+      it 'accepts trailing comma after a heredoc' do
         expect_no_offenses(<<-RUBY.strip_indent)
           route(help: {
-            'auth' => <<-HELP.chomp
+            'auth' => <<-HELP.chomp,
           ...
           HELP
           })