Prevent the transformation of multiline do-end blocks to single-line blocks with curly braces by syntax_tree

Author: i-tsvetkov

lib/erb/formatter.rb

@@ -268,8 +268,11 @@ def format_code_with_rubocop(code, line_width)
 
   def format_ruby(code, autoclose: false, extra_indent: 0)
     if autoclose
-      code += "\nend" unless ERB_OPEN_BLOCK["#{code}\nend"]
-      code += "\n}" unless ERB_OPEN_BLOCK["#{code}\n}"]
+      # A long placeholder is added to prevent the transformation of
+      # multiline do-end blocks to single-line blocks with curly braces by syntax_tree.
+      placeholder = "placeholder_#{SecureRandom.hex(@line_width / 2)}"
+      code += "\n#{placeholder}\nend" unless ERB_OPEN_BLOCK["#{code}\nend"]
+      code += "\n#{placeholder}\n}" unless ERB_OPEN_BLOCK["#{code}\n}"]
     end
 
     p RUBY_IN_: code if @debug
@@ -279,8 +282,8 @@ def format_ruby(code, autoclose: false, extra_indent: 0)
       @line_width - (indentation_width + extra_indent)
     )
 
+    formatted = formatted.split(placeholder).first.rstrip if autoclose
     lines = formatted.lines(chomp: true)
-    lines.delete_at(-1) if autoclose
 
     indent = "\s" * extra_indent
 

test/fixtures/short-do-end-block.html.erb

@@ -0,0 +1,3 @@
+<% [1, 2, 3].each do |i| %>
+  <%= i %>
+<% end %>

test/fixtures/short-do-end-block.html.expected.erb

@@ -0,0 +1,3 @@
+<% [1, 2, 3].each do |i| %>
+  <%= i %>
+<% end %>