x.json2.decoder2: support fully struct attributes (#22741)

vlib/x/json2/decoder2/attributes_test.v

@@ -0,0 +1,99 @@
+import x.json2.decoder2 as json
+
+struct StruWithJsonAttribute {
+	a     int
+	name2 string @[json: 'name']
+	b     int
+}
+
+struct StruWithSkipAttribute {
+	a    int
+	name ?string @[skip]
+	b    int
+}
+
+struct StruWithJsonSkipAttribute {
+	a    int
+	name ?string @[json: '-']
+	b    int
+}
+
+struct StruWithOmitemptyAttribute {
+	a    int
+	name ?string @[omitempty]
+	b    int
+}
+
+struct StruWithRawAttribute {
+	a      int
+	name   string @[raw]
+	object string @[raw]
+	b      int
+}
+
+struct StruWithRequiredAttribute {
+	a                 int
+	name              string  @[required]
+	skip_and_required ?string @[required; skip]
+	b                 int
+}
+
+fn test_skip_and_rename_attributes() {
+	assert json.decode[StruWithJsonAttribute]('{"name": "hola1", "a": 2, "b": 3}')! == StruWithJsonAttribute{
+		a:     2
+		name2: 'hola1'
+		b:     3
+	}, '`json` attribute not working'
+
+	assert json.decode[StruWithSkipAttribute]('{"name": "hola2", "a": 2, "b": 3}')! == StruWithSkipAttribute{
+		a:    2
+		name: none
+		b:    3
+	}, '`skip` attribute not working'
+
+	assert json.decode[StruWithJsonSkipAttribute]('{"name": "hola3", "a": 2, "b": 3}')! == StruWithJsonSkipAttribute{
+		a:    2
+		name: none
+		b:    3
+	}, " `json: '-'` skip attribute not working"
+
+	assert json.decode[StruWithOmitemptyAttribute]('{"name": "", "a": 2, "b": 3}')! == StruWithOmitemptyAttribute{
+		a:    2
+		name: none
+		b:    3
+	}, '`omitempty` attribute not working'
+
+	assert json.decode[StruWithOmitemptyAttribute]('{"name": "hola", "a": 2, "b": 3}')! == StruWithOmitemptyAttribute{
+		a:    2
+		name: 'hola'
+		b:    3
+	}, '`omitempty` attribute not working'
+}
+
+fn test_raw_attribute() {
+	assert json.decode[StruWithRawAttribute]('{"name": "hola", "a": 2, "object": {"c": 4, "d": 5}, "b": 3}')! == StruWithRawAttribute{
+		a:      2
+		name:   '"hola"'
+		object: '{"c": 4, "d": 5}'
+		b:      3
+	}, '`raw` attribute not working'
+}
+
+fn test_required_attribute() {
+	assert json.decode[StruWithRequiredAttribute]('{"name": "hola", "a": 2, "skip_and_required": "hola", "b": 3}')! == StruWithRequiredAttribute{
+		a:                 2
+		name:              'hola'
+		skip_and_required: none
+		b:                 3
+	}, '`required` attribute not working'
+
+	mut has_error := false
+
+	json.decode[StruWithRequiredAttribute]('{"name": "hola", "a": 2, "b": 3}') or {
+		has_error = true
+		assert err.msg() == 'missing required field `skip_and_required`'
+	}
+
+	assert has_error, '`required` attribute not working. It should have failed'
+	has_error = false
+}