1 files changed, 43 insertions, 0 deletions
diff --git a/internal/config/fuzz_print_test.go b/internal/config/fuzz_print_test.go
new file mode 100644
index 0000000..7f1606b
--- /dev/null
+++ b/internal/config/fuzz_print_test.go
@@ -0,0 +1,43 @@
+// SPDX-License-Identifier: GPL-3.0-or-later
+
+package config
+
+import "testing"
+
+// FuzzPrintRule: whatever rule text parses, printing it gives text that
+// parses to the same rule and prints identically, so a GUI that rewrites one
+// rule never changes what it means.
+func FuzzPrintRule(f *testing.F) {
+	for _, s := range []string{
+		`(rule "a" (move "Out"))`,
+		`(rule "b" (when (not (name "^x"))) (copy "~/b") (delete))`,
+		`(rule "c" (when (duplicate "~/d")) (move "Dupes") (stop))`,
+		`(rule "d" (when (and (type pdf) (or (size > 1M) (age < 2d)))) (rename "{stem}-x{ext}"))`,
+		`(rule "e" (case strict) (fold no) (on-conflict overwrite) (copy "X"))`,
+	} {
+		f.Add(s)
+	}
+	f.Fuzz(func(t *testing.T, s string) {
+		dir, errs := ParseDir("dl", "dl.conf", []byte("(path \"/tmp\")\n"+s))
+		if len(errs) > 0 || len(dir.Rules) != 1 {
+			return
+		}
+		out := PrintRule(dir.Rules[0])
+		again, errs := ParseDir("dl", "dl.conf", []byte("(path \"/tmp\")\n"+out))
+		if len(errs) > 0 || len(again.Rules) != 1 {
+			t.Fatalf("printed %q does not parse: %v", out, errs)
+		}
+		if got := PrintRule(again.Rules[0]); got != out {
+			t.Fatalf("printing %q is not stable: %q", out, got)
+		}
+		a, b := dir.Rules[0], again.Rules[0]
+		if a.Name != b.Name || a.HasWhen != b.HasWhen || a.Stop != b.Stop || len(a.Actions) != len(b.Actions) || len(a.When) != len(b.When) {
+			t.Fatalf("printing %q changed the rule: %+v vs %+v", out, a, b)
+		}
+		for i := range a.Actions {
+			if a.Actions[i].Kind != b.Actions[i].Kind || a.Actions[i].Arg != b.Actions[i].Arg {
+				t.Fatalf("printing %q changed action %d: %+v vs %+v", out, i, a.Actions[i], b.Actions[i])
+			}
+		}
+	})
+}