json2: fix decode to map doesn't work (#17757)

vlib/x/json2/json2.v

@@ -21,8 +21,8 @@ pub fn fast_raw_decode(src string) !Any {
 // decode is a generic function that decodes a JSON string into the target type.
 pub fn decode[T](src string) !T {
 	mut typ := T{}
+	res := raw_decode(src)!.as_map()
 	$if T is $struct {
-		res := raw_decode(src)!.as_map()
 		$for field in T.fields {
 			mut json_name := field.name
 			for attr in field.attrs {
@@ -132,7 +132,20 @@ pub fn decode[T](src string) !T {
 			}
 		}
 	} $else $if T is $map {
-		return error('Decode map is not allowed for now')
+		for k, v in res {
+			// // TODO - make this work to decode types like `map[string]StructType[bool]`
+			// $if typeof(typ[k]).idx is string {
+			// 	typ[k] = v.str()
+			// } $else $if typeof(typ[k]).idx is $struct {
+
+			// }
+			match v {
+				string {
+					typ[k] = v.str()
+				}
+				else {}
+			}
+		}
 	}
 	return typ
 }

vlib/x/json2/json2_test.v

@@ -121,3 +121,17 @@ fn test_struct_with_struct_to_map() {
 	assert json.map_from(StructType[StructType[string]]{StructType[string]{'3'}}).str() == '{"val":{"val":"3"}}'
 	assert json.map_from(StructType[StructType[int]]{StructType[int]{3}}).str() == '{"val":{"val":3}}'
 }
+
+fn test_maps() {
+	assert json.decode[map[string]string]('{"test":"abc"}') or {
+		dump(err)
+		assert false
+	} == {
+		'test': 'abc'
+	}
+
+	// assert json.decode[map[string]StructType[bool]]('{"test":{"val":true}}') or {
+	// 	dump(err)
+	// 	assert false
+	// } == {"test":StructType[bool]{true}}
+}