From 8e1a12b8c2f960e814ecaa118c287316ddd2a1b2 Mon Sep 17 00:00:00 2001
From: Natasha Sarkar <natashasarkar@google.com>
Date: Fri, 25 Jun 2021 11:02:58 -0700
Subject: [PATCH] fix leading newline issue

---
 emitterc.go    | 25 ++++++++++++++-----------
 encode_test.go | 14 ++++++++++++++
 2 files changed, 28 insertions(+), 11 deletions(-)

diff --git a/emitterc.go b/emitterc.go
index caba6e33..f0f3d186 100644
--- a/emitterc.go
+++ b/emitterc.go
@@ -491,7 +491,7 @@ func yaml_emitter_emit_document_content(emitter *yaml_emitter_t, event *yaml_eve
 	if !yaml_emitter_emit_node(emitter, event, true, false, false, false) {
 		return false
 	}
-	if !yaml_emitter_process_line_comment(emitter) {
+	if !yaml_emitter_process_line_comment(emitter, false) {
 		return false
 	}
 	if !yaml_emitter_process_foot_comment(emitter) {
@@ -560,7 +560,7 @@ func yaml_emitter_emit_flow_sequence_item(emitter *yaml_emitter_t, event *yaml_e
 		if !yaml_emitter_write_indicator(emitter, []byte{']'}, false, false, false) {
 			return false
 		}
-		if !yaml_emitter_process_line_comment(emitter) {
+		if !yaml_emitter_process_line_comment(emitter, false) {
 			return false
 		}
 		if !yaml_emitter_process_foot_comment(emitter) {
@@ -605,7 +605,7 @@ func yaml_emitter_emit_flow_sequence_item(emitter *yaml_emitter_t, event *yaml_e
 			return false
 		}
 	}
-	if !yaml_emitter_process_line_comment(emitter) {
+	if !yaml_emitter_process_line_comment(emitter, false) {
 		return false
 	}
 	if !yaml_emitter_process_foot_comment(emitter) {
@@ -646,7 +646,7 @@ func yaml_emitter_emit_flow_mapping_key(emitter *yaml_emitter_t, event *yaml_eve
 		if !yaml_emitter_write_indicator(emitter, []byte{'}'}, false, false, false) {
 			return false
 		}
-		if !yaml_emitter_process_line_comment(emitter) {
+		if !yaml_emitter_process_line_comment(emitter, false) {
 			return false
 		}
 		if !yaml_emitter_process_foot_comment(emitter) {
@@ -719,7 +719,7 @@ func yaml_emitter_emit_flow_mapping_value(emitter *yaml_emitter_t, event *yaml_e
 			return false
 		}
 	}
-	if !yaml_emitter_process_line_comment(emitter) {
+	if !yaml_emitter_process_line_comment(emitter, false) {
 		return false
 	}
 	if !yaml_emitter_process_foot_comment(emitter) {
@@ -757,7 +757,7 @@ func yaml_emitter_emit_block_sequence_item(emitter *yaml_emitter_t, event *yaml_
 	if !yaml_emitter_emit_node(emitter, event, false, true, false, false) {
 		return false
 	}
-	if !yaml_emitter_process_line_comment(emitter) {
+	if !yaml_emitter_process_line_comment(emitter, false) {
 		return false
 	}
 	if !yaml_emitter_process_foot_comment(emitter) {
@@ -833,7 +833,7 @@ func yaml_emitter_emit_block_mapping_value(emitter *yaml_emitter_t, event *yaml_
 		} else if event.sequence_style() != yaml_FLOW_SEQUENCE_STYLE && (event.typ == yaml_MAPPING_START_EVENT || event.typ == yaml_SEQUENCE_START_EVENT) {
 			// An indented block follows, so write the comment right now.
 			emitter.line_comment, emitter.key_line_comment = emitter.key_line_comment, emitter.line_comment
-			if !yaml_emitter_process_line_comment(emitter) {
+			if !yaml_emitter_process_line_comment(emitter, false) {
 				return false
 			}
 			emitter.line_comment, emitter.key_line_comment = emitter.key_line_comment, emitter.line_comment
@@ -843,7 +843,7 @@ func yaml_emitter_emit_block_mapping_value(emitter *yaml_emitter_t, event *yaml_
 	if !yaml_emitter_emit_node(emitter, event, false, false, true, false) {
 		return false
 	}
-	if !yaml_emitter_process_line_comment(emitter) {
+	if !yaml_emitter_process_line_comment(emitter, false) {
 		return false
 	}
 	if !yaml_emitter_process_foot_comment(emitter) {
@@ -1149,8 +1149,11 @@ func yaml_emitter_process_head_comment(emitter *yaml_emitter_t) bool {
 }
 
 // Write an line comment.
-func yaml_emitter_process_line_comment(emitter *yaml_emitter_t) bool {
+func yaml_emitter_process_line_comment(emitter *yaml_emitter_t, linebreak bool) bool {
 	if len(emitter.line_comment) == 0 {
+		if linebreak && !put_break(emitter) {
+			return false
+		}
 		return true
 	}
 	if !emitter.whitespace {
@@ -1899,7 +1902,7 @@ func yaml_emitter_write_literal_scalar(emitter *yaml_emitter_t, value []byte) bo
 	if !yaml_emitter_write_block_scalar_hints(emitter, value) {
 		return false
 	}
-	if !yaml_emitter_process_line_comment(emitter) {
+	if !yaml_emitter_process_line_comment(emitter, true) {
 		return false
 	}
 	//emitter.indention = true
@@ -1936,7 +1939,7 @@ func yaml_emitter_write_folded_scalar(emitter *yaml_emitter_t, value []byte) boo
 	if !yaml_emitter_write_block_scalar_hints(emitter, value) {
 		return false
 	}
-	if !yaml_emitter_process_line_comment(emitter) {
+	if !yaml_emitter_process_line_comment(emitter, true) {
 		return false
 	}
 
diff --git a/encode_test.go b/encode_test.go
index c941e0de..3de4b14c 100644
--- a/encode_test.go
+++ b/encode_test.go
@@ -790,6 +790,20 @@ func (s *S) TestCompactSequenceWithSetIndent(c *C) {
 `)
 }
 
+func (s *S) TestNewLinePreserved(c *C) {
+	obj := &marshalerValue{}
+	obj.Field.value = "a:\n        b:\n                c: d\n"
+	data, err := yaml.Marshal(obj)
+	c.Assert(err, IsNil)
+	c.Assert(string(data), Equals, "_: |\n    a:\n            b:\n                    c: d\n")
+
+	obj.Field.value = "\na:\n        b:\n                c: d\n"
+	data, err = yaml.Marshal(obj)
+	c.Assert(err, IsNil)
+	// the newline at the start of the file should be preserved
+	c.Assert(string(data), Equals, "_: |4\n\n    a:\n            b:\n                    c: d\n")
+}
+
 func (s *S) TestSortedOutput(c *C) {
 	order := []interface{}{
 		false,