From 0d35f0948c2a9530edc172e4676a15e73420d165 Mon Sep 17 00:00:00 2001
From: larpon <768942+larpon@users.noreply.github.com>
Date: Wed, 4 Sep 2024 22:13:50 +0200
Subject: [PATCH] flag: correct bool logic, add test (#22162)

---
 vlib/flag/flag_to.v           |  3 ++-
 vlib/flag/flag_to_bool_test.v | 21 +++++++++++++++++++++
 2 files changed, 23 insertions(+), 1 deletion(-)
 create mode 100644 vlib/flag/flag_to_bool_test.v

diff --git a/vlib/flag/flag_to.v b/vlib/flag/flag_to.v
index be97ff447a..d8094ce2ff 100644
--- a/vlib/flag/flag_to.v
+++ b/vlib/flag/flag_to.v
@@ -832,6 +832,7 @@ fn keep_at_max(str string, max int) string {
 pub fn (fm FlagMapper) to_struct[T](defaults ?T) !T {
 	// Generate T result
 	mut result := defaults or { T{} }
+	the_default := defaults or { T{} }
 
 	$if T is $struct {
 		struct_name := T.name
@@ -907,7 +908,7 @@ pub fn (fm FlagMapper) to_struct[T](defaults ?T) !T {
 					if arg := f.arg {
 						return error('can not assign `${arg}` to bool field `${field.name}`')
 					}
-					result.$(field.name) = true
+					result.$(field.name) = !the_default.$(field.name)
 				} $else $if field.typ is string {
 					trace_dbg_println('${@FN}: assigning (string) ${struct_name}.${field.name} = ${f.arg or {
 						'ERROR'
diff --git a/vlib/flag/flag_to_bool_test.v b/vlib/flag/flag_to_bool_test.v
new file mode 100644
index 0000000000..b8784c52a3
--- /dev/null
+++ b/vlib/flag/flag_to_bool_test.v
@@ -0,0 +1,21 @@
+import flag
+
+const gnu_args_bool_flags = ['--no-parallel', '--nocache', '--stay', '--nix']
+
+struct BoolConfig {
+	mix      bool
+	nix      bool
+	parallel bool = true @[long: 'no-parallel']
+	cache    bool @[long: nocache]
+	no_stay  bool @[long: 'stay']
+}
+
+fn test_bool_flags() {
+	bf, _ := flag.to_struct[BoolConfig](gnu_args_bool_flags, style: .long)!
+
+	assert bf.mix == false
+	assert bf.nix == true
+	assert bf.parallel == false
+	assert bf.cache == true
+	assert bf.no_stay == true
+}