From f095adc67efd91225419cec61da3ea0fd59f3b66 Mon Sep 17 00:00:00 2001
From: Ary Borenszweig <asterite@gmail.com>
Date: Tue, 29 Sep 2020 12:05:34 -0300
Subject: [PATCH] Formatter: handle comment before do in a separate line
 (#9762)

---
 spec/compiler/formatter/formatter_spec.cr | 13 ++++++++++++
 src/compiler/crystal/tools/formatter.cr   | 25 ++++++++++++++++++++---
 2 files changed, 35 insertions(+), 3 deletions(-)

diff --git a/spec/compiler/formatter/formatter_spec.cr b/spec/compiler/formatter/formatter_spec.cr
index 176de863ef03..e9b98f9d17c4 100644
--- a/spec/compiler/formatter/formatter_spec.cr
+++ b/spec/compiler/formatter/formatter_spec.cr
@@ -1728,4 +1728,17 @@ describe Crystal::Formatter do
     def bar
     end
     CODE
+
+  assert_format <<-CODE
+    foo 1, # comment
+      do
+      end
+    CODE
+
+  assert_format <<-CODE
+    foo 1, # comment
+      # bar
+      do
+      end
+    CODE
 end
diff --git a/src/compiler/crystal/tools/formatter.cr b/src/compiler/crystal/tools/formatter.cr
index c3f77c2fb72d..1ee111617518 100644
--- a/src/compiler/crystal/tools/formatter.cr
+++ b/src/compiler/crystal/tools/formatter.cr
@@ -2906,18 +2906,37 @@ module Crystal
       old_inside_call_or_assign = @inside_call_or_assign
       @inside_call_or_assign = 0
 
+      comma_before_comment = false
+
       if @token.type == :","
-        needs_comma = true
-        next_token_skip_space_or_newline
+        next_token
+        next_token if @token.type == :SPACE
+        if @token.type == :COMMENT
+          write ","
+          needs_comma = false
+          comma_before_comment = true
+          @indent += 2
+        else
+          needs_comma = true
+        end
+        skip_space_or_newline
+        @indent -= 2 if comma_before_comment
       end
 
       if @token.keyword?(:do)
-        write " do"
+        if comma_before_comment
+          @indent += 2
+          write_indent
+        else
+          write " "
+        end
+        write "do"
         next_token_skip_space
         body = format_block_args node.args, node
         old_implicit_exception_handler_indent, @implicit_exception_handler_indent = @implicit_exception_handler_indent, @indent
         format_nested_with_end body
         @implicit_exception_handler_indent = old_implicit_exception_handler_indent
+        @indent -= 2
       elsif @token.type == :"{"
         write "," if needs_comma
         write " {"