text/diff: skip writing Unified if no difference found

2 files changed, 17 insertions, 0 deletions

diff --git a/lib/text/diff/diff_test.go b/lib/text/diff/diff_test.go
index 001e962c..d2009bfe 100644
--- a/lib/text/diff/diff_test.go
+++ b/lib/text/diff/diff_test.go
@@ -219,3 +219,17 @@ func TestFiles_LevelChunks(t *testing.T) {
 		}
 	}
 }
+
+func TestUnified_WithNewLine(t *testing.T) {
+	exp := "a\nb"
+	got := "a\nb\n"
+
+	var sb strings.Builder
+	diff := Unified([]byte(exp), []byte(got))
+	if diff.IsMatched {
+		return
+	}
+	diff.WriteUnified(&sb, 3)
+
+	t.Fatalf(`sb: %s`, sb.String())
+}
diff --git a/lib/text/diff/unified.go b/lib/text/diff/unified.go
index 17eed2c2..1ed58c35 100644
--- a/lib/text/diff/unified.go
+++ b/lib/text/diff/unified.go
@@ -105,6 +105,9 @@ func findInsertIndex(unified []Line, next *Line, start int) (idx int) {
 // The ncontext must be 0 or positive, otherwise it will be set to 0 (no
 // context added).
 func (diff Data) WriteUnified(w io.Writer, ncontext int) (err error) {
+	if len(diff.Unified) == 0 {
+		return nil
+	}
 	if ncontext < 0 {
 		ncontext = 0
 	}