From 9dec65ca6cd4c6699c58fad0457d9a21b93ead26 Mon Sep 17 00:00:00 2001
From: Alexander Medvednikov <alexander@medvednikov.com>
Date: Tue, 21 Apr 2026 05:23:13 +0300
Subject: [PATCH] x.json2: fix @[json_as_number] enum attribute silently
 ignored on encode (fixes #26906)

---
 vlib/x/json2/README.md           |  3 +++
 vlib/x/json2/attr_utils.v        | 10 ++++++++++
 vlib/x/json2/encode.v            |  4 ++--
 vlib/x/json2/tests/encode_test.v | 18 ++++++++++++++++++
 4 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/vlib/x/json2/README.md b/vlib/x/json2/README.md
index 4a3f17f09..7ec32b443 100644
--- a/vlib/x/json2/README.md
+++ b/vlib/x/json2/README.md
@@ -29,6 +29,9 @@ fn main() {
 }
 ```
 
+Enums encode as strings by default. Use `@[json_as_number]` on an enum to emit
+its integer value instead.
+
 #### decode[T]
 
 ```v
diff --git a/vlib/x/json2/attr_utils.v b/vlib/x/json2/attr_utils.v
index b3b853694..0ac790496 100644
--- a/vlib/x/json2/attr_utils.v
+++ b/vlib/x/json2/attr_utils.v
@@ -41,3 +41,13 @@ fn json_attr_value_range(attr string) ?(int, int) {
 	}
 	return start, end
 }
+
+@[inline]
+fn enum_uses_json_as_number[T]() bool {
+	$for attr in T.attributes {
+		if attr.name == 'json_as_number' {
+			return true
+		}
+	}
+	return false
+}
diff --git a/vlib/x/json2/encode.v b/vlib/x/json2/encode.v
index b0159b95b..838909d0e 100644
--- a/vlib/x/json2/encode.v
+++ b/vlib/x/json2/encode.v
@@ -112,7 +112,7 @@ fn (mut encoder Encoder) encode_value[T](val T) {
 		}
 		encoder.output << `}`
 	} $else $if T.unaliased_typ is $enum {
-		if encoder.enum_as_int {
+		if encoder.enum_as_int || enum_uses_json_as_number[T]() {
 			encoder.encode_number(int(val))
 		} else {
 			mut enum_val := 'unknown enum value'
@@ -408,7 +408,7 @@ fn (mut encoder Encoder) encode_map[K, T](val map[K]T) {
 }
 
 fn (mut encoder Encoder) encode_enum[T](val T) {
-	if encoder.enum_as_int {
+	if encoder.enum_as_int || enum_uses_json_as_number[T]() {
 		encoder.encode_number(int(val))
 	} else {
 		mut enum_val := 'unknown enum value'
diff --git a/vlib/x/json2/tests/encode_test.v b/vlib/x/json2/tests/encode_test.v
index 856155854..04c1c73f1 100644
--- a/vlib/x/json2/tests/encode_test.v
+++ b/vlib/x/json2/tests/encode_test.v
@@ -16,6 +16,12 @@ enum TestEnum {
 
 type EnumAlias = TestEnum
 
+@[json_as_number]
+enum NumberedTestEnum {
+	a
+	b = 5
+}
+
 type Sum = int | string
 type SumAlias = Sum
 
@@ -25,6 +31,10 @@ struct Basic {
 	c bool
 }
 
+struct NumberedEnumWrap {
+	a NumberedTestEnum
+}
+
 type BasicAlias = Basic
 
 struct Opt {
@@ -142,6 +152,14 @@ fn test_enums() {
 	assert json.encode(EnumAlias(TestEnum.d)) == '"d"'
 }
 
+fn test_enum_json_as_number_attribute() {
+	assert json.encode(NumberedTestEnum.a) == '0'
+	assert json.encode(NumberedTestEnum.b) == '5'
+	assert json.encode(NumberedEnumWrap{
+		a: .a
+	}) == '{"a":0}'
+}
+
 fn test_sumtypes() {
 	assert json.encode(Sum(10)) == '10'
 	assert json.encode(Sum('hi')) == '"hi"'
-- 
2.39.5