#utils #ron #functional #error-handling #type #progress #error-reporting

bin+lib ron-utils

Utilities for working with Rusty Object Notation (RON) files

7 releases

0.1.0-preview8 Oct 25, 2021
0.1.0-preview7 Oct 24, 2021
0.1.0-preview6 Oct 23, 2021
0.1.0-preview4 Oct 17, 2021

#2933 in Rust patterns

21 downloads per month



EXPERIMENT: Rusty Object Notation reboot

Experimental implementation of a new parser for RON using small functional parsers for individual syntax elements over a stateful parser.

This experiment started off as "RON + nom", but is now using its own parsers & combinators inspired by nom.


The current ron parsing suffers from the following problems:

  • parsing is done in both parse.rs and the deserializer itself
    • bad code organization
    • hard to maintain
    • limits reuse
  • serde's data model stops us from accurately reflecting struct / map and struct names


Stateless / functional parsers are

  • easier to maintain
  • easier to reuse
  • much easier to test

An abstract syntax tree (AST)...

  • makes the deserializer much easier & cleaner to implement
  • allows reporting locations of syntax & type errors
  • can be reused by multiple deserializer implementations (serde::Deserializer, our_own::Deserializer, ron-edit)

Error reporting

The old RON deserializer produced errors that were often hard to understand. ron-reboot is meant to change that; this is the output of a deserialization error as of 2021-10-15:

error: invalid type: boolean `true`, expected a string
 --> string:3:9
3 |       y: true,
  |          ^^^^

or with a multi-line expression:

error: invalid type: map, expected a string
 --> string:3:9
3 |       y: (
  |  ________^
4 | |         this: "is",
5 | |         not: "the right type",
6 | |     ),
  | |______^

Goals / Progress

Goal Status
Parser generating AST ✔️ done
Parser generating beautiful errors ✔️ done
Accurate Value deserialization from AST ✔️ done
Replace nom combinators ✔️ done
Spans in AST (locations for error reporting) ✔️ done
Serde Deserializer using AST ✔️ done
Serde Deserializer generating beautiful errors ✔️ done
ron-edit (format & comments preserving writer) ❌ to be done


Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, shall be licensed according to the license of this project (Apache-2.0), without any additional terms or conditions.


~49K SLoC