json: add support for aliased struct fields (#6556)

vlib/json/json_test.v

@@ -171,7 +171,6 @@ struct Data {
 
 fn test_nested_type() {
 	data_expected := '{"countries":[{"cities":[{"name":"London"},{"name":"Manchester"}],"name":"UK"},{"cities":[{"name":"Donlon"},{"name":"Termanches"}],"name":"KU"}],"users":{"Foo":{"age":10,"nums":[1,2,3],"lastName":"Johnson","IsRegistered":true,"type":0,"pet_animals":"little foo"},"Boo":{"age":20,"nums":[5,3,1],"lastName":"Smith","IsRegistered":false,"type":4,"pet_animals":"little boo"}},"extra":{"2":{"n1":2,"n2":4,"n3":8,"n4":16},"3":{"n1":3,"n2":9,"n3":27,"n4":81}}}'
-
 	data := Data{
 		countries: [
 			Country{
@@ -195,7 +194,7 @@ fn test_nested_type() {
 				is_registered: true
 				typ: 0
 				pets: 'little foo'
-			},
+			}
 			'Boo': User{
 				age: 20
 				nums: [5, 3, 1]
@@ -204,39 +203,37 @@ fn test_nested_type() {
 				typ: 4
 				pets: 'little boo'
 			}
-		},
+		}
 		extra: {
 			'2': {
 				'n1': 2
 				'n2': 4
 				'n3': 8
 				'n4': 16
-			},
+			}
 			'3': {
 				'n1': 3
 				'n2': 9
 				'n3': 27
 				'n4': 81
-			},
+			}
 		}
 	}
 	out := json.encode(data)
 	println(out)
 	assert out == data_expected
-
 	data2 := json.decode(Data, data_expected) or {
 		assert false
 		Data{}
 	}
 	assert data2.countries.len == data.countries.len
-	for i in 0..1 {
+	for i in 0 .. 1 {
 		assert data2.countries[i].name == data.countries[i].name
 		assert data2.countries[i].cities.len == data.countries[i].cities.len
-		for j in 0..1 {
+		for j in 0 .. 1 {
 			assert data2.countries[i].cities[j].name == data.countries[i].cities[j].name
 		}
 	}
-
 	for key, user in data.users {
 		assert data2.users[key].age == user.age
 		assert data2.users[key].nums == user.nums
@@ -245,7 +242,6 @@ fn test_nested_type() {
 		assert data2.users[key].typ == user.typ
 		// assert data2.users[key].pets == user.pets // TODO FIX
 	}
-
 	for k, v in data.extra {
 		for k2, v2 in v {
 			assert data2.extra[k][k2] == v2
@@ -263,11 +259,9 @@ fn test_generic_struct() {
 	foo_int := Foo<int>{'bar', 12}
 	foo_enc := json.encode(foo_int)
 	assert foo_enc == '{"name":"bar","data":12}'
-
 	foo_dec := json.decode(Foo<int>, foo_enc) or {
 		exit(1)
 	}
-
 	assert foo_dec.name == 'bar'
 	assert foo_dec.data == 12
 }
@@ -275,7 +269,6 @@ fn test_generic_struct() {
 fn test_errors() {
 	invalid_array := fn () {
 		data := '{"countries":[{"cities":[{"name":"London"},{"name":"Manchester"}],"name":"UK"},{"cities":{"name":"Donlon"},"name":"KU"}],"users":{"Foo":{"age":10,"nums":[1,2,3],"lastName":"Johnson","IsRegistered":true,"type":0,"pet_animals":"little foo"},"Boo":{"age":20,"nums":[5,3,1],"lastName":"Smith","IsRegistered":false,"type":4,"pet_animals":"little boo"}},"extra":{"2":{"n1":2,"n2":4,"n3":8,"n4":16},"3":{"n1":3,"n2":9,"n3":27,"n4":81}}}'
-
 		json.decode(Data, data) or {
 			println(err)
 			assert err.starts_with('Json element is not an array:')
@@ -283,9 +276,8 @@ fn test_errors() {
 		}
 		assert false
 	}
-	invalid_object := fn() {
+	invalid_object := fn () {
 		data := '{"countries":[{"cities":[{"name":"London"},{"name":"Manchester"}],"name":"UK"},{"cities":[{"name":"Donlon"},{"name":"Termanches"}],"name":"KU"}],"users":[{"age":10,"nums":[1,2,3],"lastName":"Johnson","IsRegistered":true,"type":0,"pet_animals":"little foo"},{"age":20,"nums":[5,3,1],"lastName":"Smith","IsRegistered":false,"type":4,"pet_animals":"little boo"}],"extra":{"2":{"n1":2,"n2":4,"n3":8,"n4":16},"3":{"n1":3,"n2":9,"n3":27,"n4":81}}}'
-
 		json.decode(Data, data) or {
 			println(err)
 			assert err.starts_with('Json element is not an object:')
@@ -296,3 +288,25 @@ fn test_errors() {
 	invalid_array()
 	invalid_object()
 }
+
+type ID = string
+
+struct Message {
+	id ID
+}
+
+fn test_decode_alias_struct() {
+	msg := json.decode(Message, '{"id": "118499178790780929"}') or {
+		assert false
+		Message{}
+	}
+	// hacky way of comparing aliased strings
+	assert msg.id.str() == '118499178790780929'
+}
+
+fn test_encode_alias_struct() {
+	expected := '{"id":"118499178790780929"}'
+	msg := Message{'118499178790780929'}
+	out := json.encode(msg)
+	assert out == expected
+}