From 885e3f19bd27ed592ccee0a07013f63dab1bbe7b Mon Sep 17 00:00:00 2001
From: Simon Frei <freisim93@gmail.com>
Date: Sat, 20 Jan 2018 07:52:57 +0000
Subject: [PATCH] lib/ignores: Update lines even if patterns didn't change
 (fixes #4689)

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/4690
---
 lib/ignore/ignore.go      |  3 ++-
 lib/ignore/ignore_test.go | 25 +++++++++++++++++++++++++
 2 files changed, 27 insertions(+), 1 deletion(-)

diff --git a/lib/ignore/ignore.go b/lib/ignore/ignore.go
index 224716574..e1a833ed2 100644
--- a/lib/ignore/ignore.go
+++ b/lib/ignore/ignore.go
@@ -156,6 +156,8 @@ func (m *Matcher) parseLocked(r io.Reader, file string) error {
 	// Error is saved and returned at the end. We process the patterns
 	// (possibly blank) anyway.
 
+	m.lines = lines
+
 	newHash := hashPatterns(patterns)
 	if newHash == m.curHash {
 		// We've already loaded exactly these patterns.
@@ -163,7 +165,6 @@ func (m *Matcher) parseLocked(r io.Reader, file string) error {
 	}
 
 	m.curHash = newHash
-	m.lines = lines
 	m.patterns = patterns
 	if m.withCache {
 		m.matches = newCache(patterns)
diff --git a/lib/ignore/ignore_test.go b/lib/ignore/ignore_test.go
index 108687c78..f15ffd9ba 100644
--- a/lib/ignore/ignore_test.go
+++ b/lib/ignore/ignore_test.go
@@ -956,3 +956,28 @@ func TestIssue4680(t *testing.T) {
 		}
 	}
 }
+
+func TestIssue4689(t *testing.T) {
+	stignore := `// orig`
+
+	pats := New(fs.NewFilesystem(fs.FilesystemTypeBasic, "."), WithCache(true))
+	err := pats.Parse(bytes.NewBufferString(stignore), ".stignore")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if lines := pats.Lines(); len(lines) != 1 || lines[0] != "// orig" {
+		t.Fatalf("wrong lines parsing original comment:\n%q", lines)
+	}
+
+	stignore = `// new`
+
+	err = pats.Parse(bytes.NewBufferString(stignore), ".stignore")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	if lines := pats.Lines(); len(lines) != 1 || lines[0] != "// new" {
+		t.Fatalf("wrong lines parsing changed comment:\n%v", lines)
+	}
+}