Convert EOL to UNIX-style to render MD properly

modules/markup/markdown/markdown.go

@@ -157,7 +157,8 @@ func RenderRaw(body []byte, urlPrefix string, wikiMarkdown bool) []byte {
 		exts |= blackfriday.HardLineBreak
 	}
 
-	body = blackfriday.Run(body, blackfriday.WithRenderer(renderer), blackfriday.WithExtensions(exts))
+	// Need to normalize EOL to UNIX LF to have consistent results in rendering
+	body = blackfriday.Run(util.NormalizeEOL(body), blackfriday.WithRenderer(renderer), blackfriday.WithExtensions(exts))
 	return markup.SanitizeBytes(body)
 }
 

modules/util/util.go

@@ -5,6 +5,7 @@
 package util
 
 import (
+	"bytes"
 	"strings"
 )
 
@@ -63,3 +64,35 @@ func Min(a, b int) int {
 func IsEmptyString(s string) bool {
 	return len(strings.TrimSpace(s)) == 0
 }
+
+// NormalizeEOL will convert Windows (CRLF) and Mac (CR) EOLs to UNIX (LF)
+func NormalizeEOL(input []byte) []byte {
+	tmp := make([]byte, len(input))
+	left := 0
+	pos := 0
+	for left < len(input) && input[left] == '\n' {
+		left++
+	}
+	if left != 0 {
+		copy(tmp[pos:pos+left], input[0:left])
+		pos = left
+	}
+
+	for left < len(input) {
+		if input[left] == '\n' {
+			left++
+		}
+		right := bytes.IndexByte(input[left:], '\r')
+		if right == -1 {
+			copy(tmp[pos:], input[left:])
+			pos = pos + len(input) - left
+			break
+		}
+		copy(tmp[pos:pos+right], input[left:left+right])
+		pos += right
+		tmp[pos] = '\n'
+		left += right + 1
+		pos++
+	}
+	return tmp[:pos]
+}

modules/util/util_test.go

@@ -5,6 +5,7 @@
 package util
 
 import (
+	"strings"
 	"testing"
 
 	"code.gitea.io/gitea/modules/setting"
@@ -94,3 +95,59 @@ func TestIsEmptyString(t *testing.T) {
 		assert.Equal(t, v.expected, IsEmptyString(v.s))
 	}
 }
+
+func Test_NormalizeEOL(t *testing.T) {
+	data1 := []string{
+		"",
+		"This text starts with empty lines",
+		"another",
+		"",
+		"",
+		"",
+		"Some other empty lines in the middle",
+		"more.",
+		"And more.",
+		"Ends with empty lines too.",
+		"",
+		"",
+		"",
+	}
+
+	data2 := []string{
+		"This text does not start with empty lines",
+		"another",
+		"",
+		"",
+		"",
+		"Some other empty lines in the middle",
+		"more.",
+		"And more.",
+		"Ends without EOLtoo.",
+	}
+
+	buildEOLData := func(data []string, eol string) []byte {
+		return []byte(strings.Join(data, eol))
+	}
+
+	dos := buildEOLData(data1, "\r\n")
+	unix := buildEOLData(data1, "\n")
+	mac := buildEOLData(data1, "\r")
+
+	assert.Equal(t, unix, NormalizeEOL(dos))
+	assert.Equal(t, unix, NormalizeEOL(mac))
+	assert.Equal(t, unix, NormalizeEOL(unix))
+
+	dos = buildEOLData(data2, "\r\n")
+	unix = buildEOLData(data2, "\n")
+	mac = buildEOLData(data2, "\r")
+
+	assert.Equal(t, unix, NormalizeEOL(dos))
+	assert.Equal(t, unix, NormalizeEOL(mac))
+	assert.Equal(t, unix, NormalizeEOL(unix))
+
+	assert.Equal(t, []byte("one liner"), NormalizeEOL([]byte("one liner")))
+	assert.Equal(t, []byte("\n"), NormalizeEOL([]byte("\n")))
+	assert.Equal(t, []byte("\ntwo liner"), NormalizeEOL([]byte("\ntwo liner")))
+	assert.Equal(t, []byte("two liner\n"), NormalizeEOL([]byte("two liner\n")))
+	assert.Equal(t, []byte{}, NormalizeEOL([]byte{}))
+}