treat the 'No newline at end of file' message as an encoding artifact;

don't store in hunk body

Author: sqs

diff/diff_test.go

@@ -5,6 +5,7 @@ import (
 	"io/ioutil"
 	"path/filepath"
 	"reflect"
+	"strings"
 	"testing"
 )
 
@@ -158,3 +159,33 @@ func TestParseMultiFileDiffAndPrintMultiFileDiff(t *testing.T) {
 		}
 	}
 }
+
+func TestNoNewlineAtEnd(t *testing.T) {
+	orig := `@@ -1,1 +1,1 @@
+-b
++b
+\ No newline at end of file
+`
+
+	hunks, err := ParseHunks([]byte(orig))
+	if err != nil {
+		t.Fatal("ParseHunks: %s", err)
+	}
+
+	for _, hunk := range hunks {
+		if body := string(hunk.Body); strings.Contains(body, "No newline") {
+			t.Errorf("after parse, hunk body contains 'No newline...' string\n\nbody is:\n%q", body)
+		}
+		if bytes.HasSuffix(hunk.Body, []byte{'\n'}) {
+			t.Errorf("after parse, hunk body ends with newline\n\nbody is:\n%q", hunk.Body)
+		}
+
+		printed, err := PrintHunks(hunks)
+		if err != nil {
+			t.Fatal("PrintHunks: %s", err)
+		}
+		if printed := string(printed); printed != orig {
+			t.Errorf("printed diff hunks != original diff hunks\n\n# PrintHunks output:\n%q\n\n# Original:\n%q", printed, orig)
+		}
+	}
+}

diff/parse.go

@@ -391,7 +391,7 @@ func (r *HunksReader) ReadHunk() (*Hunk, error) {
 				// handle that case.
 				return r.hunk, &ParseError{r.line, r.offset, &ErrBadHunkLine{Line: line}}
 			}
-			if string(line) == noNewlineMessage {
+			if bytes.Equal(line, []byte(noNewlineMessage)) {
 				// Remove previous line's newline.
 				if len(r.hunk.Body) != 0 {
 					r.hunk.Body = r.hunk.Body[:len(r.hunk.Body)-1]
@@ -414,7 +414,7 @@ func (r *HunksReader) ReadHunk() (*Hunk, error) {
 	return nil, io.EOF
 }
 
-const noNewlineMessage = "\\ No newline at end of file\n"
+const noNewlineMessage = `\ No newline at end of file`
 
 // linePrefixes is the set of all characters a valid line in a diff
 // hunk can start with. '\' can appear in diffs when no newline is

diff/print.go

@@ -86,13 +86,20 @@ func PrintHunks(hunks []*Hunk) ([]byte, error) {
 		if _, err := fmt.Fprintln(&buf); err != nil {
 			return nil, err
 		}
-		if len(hunk.Body) != 0 && hunk.Body[len(hunk.Body)-1] != '\n' {
-			// Append message if hunk.Body doesn't end with a newline.
-			hunk.Body = append(hunk.Body, noNewlineMessage...)
-		}
 		if _, err := buf.Write(hunk.Body); err != nil {
 			return nil, err
 		}
+		if !bytes.HasSuffix(hunk.Body, []byte{'\n'}) {
+			if _, err := fmt.Fprintln(&buf); err != nil {
+				return nil, err
+			}
+			if _, err := buf.Write([]byte(noNewlineMessage)); err != nil {
+				return nil, err
+			}
+			if _, err := fmt.Fprintln(&buf); err != nil {
+				return nil, err
+			}
+		}
 	}
 	return buf.Bytes(), nil
 }