From 1d81c00a2750c87cee0e6445fe3a13d72b75bd69 Mon Sep 17 00:00:00 2001
From: Daniel Vandersluis <daniel.vandersluis@gmail.com>
Date: Sat, 15 May 2021 12:07:24 -0400
Subject: [PATCH] [Fix #9799] Fix invalid line splitting by `Layout/LineLength`
 for `send` nodes with heredoc arguments.

---
 .../fix_fix_invalid_line_splitting_by.md      |  1 +
 lib/rubocop/cop/mixin/check_line_breakable.rb | 16 +++++++
 spec/rubocop/cop/layout/line_length_spec.rb   | 47 +++++++++++++++++++
 3 files changed, 64 insertions(+)
 create mode 100644 changelog/fix_fix_invalid_line_splitting_by.md

diff --git a/changelog/fix_fix_invalid_line_splitting_by.md b/changelog/fix_fix_invalid_line_splitting_by.md
new file mode 100644
index 00000000000..487531f53ca
--- /dev/null
+++ b/changelog/fix_fix_invalid_line_splitting_by.md
@@ -0,0 +1 @@
+* [#9799](https://github.com/rubocop/rubocop/issues/9799): Fix invalid line splitting by `Layout/LineLength` for `send` nodes with heredoc arguments. ([@dvandersluis][])
diff --git a/lib/rubocop/cop/mixin/check_line_breakable.rb b/lib/rubocop/cop/mixin/check_line_breakable.rb
index 0e6bad0a106..5a3ae63830a 100644
--- a/lib/rubocop/cop/mixin/check_line_breakable.rb
+++ b/lib/rubocop/cop/mixin/check_line_breakable.rb
@@ -76,11 +76,27 @@ def extract_first_element_over_column_limit(node, elements, max)
 
         i = 0
         i += 1 while within_column_limit?(elements[i], max, line)
+        i = shift_elements_for_heredoc_arg(node, elements, i)
+
+        return if i.nil?
         return elements.first if i.zero?
 
         elements[i - 1]
       end
 
+      # @api private
+      # If a send node contains a heredoc argument, splitting cannot happen
+      # after the heredoc or else it will cause a syntax error.
+      def shift_elements_for_heredoc_arg(node, elements, index)
+        return index unless node.send_type?
+
+        heredoc_index = elements.index { |arg| (arg.str_type? || arg.dstr_type?) && arg.heredoc? }
+        return index unless heredoc_index
+        return nil if heredoc_index.zero?
+
+        heredoc_index >= index ? index : heredoc_index + 1
+      end
+
       # @api private
       def within_column_limit?(element, max, line)
         element && element.loc.column <= max && element.loc.line == line
diff --git a/spec/rubocop/cop/layout/line_length_spec.rb b/spec/rubocop/cop/layout/line_length_spec.rb
index cc2d919cc24..726a2fefe7c 100644
--- a/spec/rubocop/cop/layout/line_length_spec.rb
+++ b/spec/rubocop/cop/layout/line_length_spec.rb
@@ -727,6 +727,53 @@ def baz(bar)
           RUBY
         end
       end
+
+      context 'with a heredoc argument' do
+        it 'does not break up the line' do
+          args = 'x' * 25
+          expect_offense(<<~RUBY, args: args)
+            foo(<<~STRING, #{args}xxx)
+                           _{args}^^^^ Line is too long. [44/40]
+            STRING
+          RUBY
+
+          expect_no_corrections
+        end
+
+        context 'and other arguments before the heredoc' do
+          it 'can break up the line before the heredoc argument' do
+            args = 'x' * 20
+            expect_offense(<<~RUBY, args: args)
+              foo(abc, <<~STRING, #{args}xxx)
+                                  _{args}^^^^ Line is too long. [44/40]
+              STRING
+            RUBY
+
+            expect_correction(<<~RUBY)
+              foo(abc,#{trailing_whitespace}
+              <<~STRING, #{args}xxx)
+              STRING
+            RUBY
+          end
+        end
+
+        context 'and the heredoc is after the line should split' do
+          it 'can break up the line before the heredoc argument' do
+            args = 'x' * 34
+            expect_offense(<<~RUBY, args: args)
+              foo(#{args}, <<~STRING)
+                  _{args}  ^^^^^^^^^^ Line is too long. [50/40]
+              STRING
+            RUBY
+
+            expect_correction(<<~RUBY)
+              foo(#{args},#{trailing_whitespace}
+              <<~STRING)
+              STRING
+            RUBY
+          end
+        end
+      end
     end
 
     context 'array' do