explain: shows a duplicate's skipped delete, leaves the cache alone, walks only for duplicate tests

1 files changed, 22 insertions, 0 deletions

diff --git a/internal/engine/exclude_test.go b/internal/engine/exclude_test.go
index ceb8442..cd1cc4b 100644
--- a/internal/engine/exclude_test.go
+++ b/internal/engine/exclude_test.go
@@ -426,3 +426,25 @@ func TestPartlyReadableDocument(t *testing.T) {
 		t.Errorf("no warning for the keyword the unreadable part might hold")
 	}
 }
+
+// TestExplainLeavesTheCacheAlone: explain never writes the keyword cache -
+// not even to remove one a directory without content tests no longer uses
+// (triage 28e: explain runs without the directory's lock).
+func TestExplainLeavesTheCacheAlone(t *testing.T) {
+	h, dl := excludeTree(t, map[string]string{"a.txt": "x"})
+	main := writeConfig(t, h, `(include "dl")`, map[string]string{"dl": "(path \"~/dl\")\n(rule \"all\" (move \"Out\"))\n"})
+	e, errs := Load(main)
+	if len(errs) > 0 {
+		t.Fatal(errs)
+	}
+	e.CacheDir = filepath.Join(h, "cache")
+	os.MkdirAll(e.CacheDir, 0o700)
+	cache := filepath.Join(e.CacheDir, "dl.cache")
+	os.WriteFile(cache, []byte("old"), 0o600)
+	if _, err := e.Explain(context.Background(), filepath.Join(dl, "a.txt")); err != nil {
+		t.Fatal(err)
+	}
+	if _, err := os.Stat(cache); err != nil {
+		t.Errorf("explain removed the cache: %v", err)
+	}
+}