use darling to parse attributes

the code is much more readable now

tests/simple.rs

@@ -4,7 +4,7 @@ use macroconf::config;
 use miniconf::{
     Error::Traversal,
     IntoKeys, JsonCoreSlash, Path,
-    Traversal::{Absent, TooLong},
+    Traversal::{Access, TooLong},
     Tree, TreeKey,
 };
 use serde::{Deserialize, Serialize};
@@ -13,11 +13,11 @@ use serde::{Deserialize, Serialize};
 #[derive(Debug, Clone, Copy, Serialize, Deserialize, Tree)]
 struct SubConfig {
     skipped: i32,
-    #[min]
+    #[config(min)]
     min: i32,
-    #[max]
+    #[config(max)]
     max: i32,
-    #[default = 0]
+    #[config(default = "0")]
     default: i32,
     /// This is a description
     description: i32,
@@ -94,9 +94,8 @@ fn serialize() {
         ("/description/value", "5"),
         ("/description/description", "\"This is a description\""),
     ] {
-        let res = config.get_json(input, &mut buffer);
-        assert_eq!(res, Ok(output.len()));
-        assert_eq!(from_utf8(&buffer[..output.len()]), Ok(output));
+        let len = config.get_json(input, &mut buffer).unwrap();
+        assert_eq!(from_utf8(&buffer[..len]), Ok(output));
     }
 }
 
@@ -132,7 +131,7 @@ fn deserialize() {
         "/description/description",
     ] {
         let res = config.set_json(input, b"10");
-        assert_eq!(res, Err(Traversal(Absent(1))));
+        assert_eq!(res, Err(Traversal(Access(1, "Cannot write limits"))));
     }
 }