posp

posp (Piece of **** parsers). These are parser implementations never meant to see production but help me practice creating parsers.

[!WARNING] These are just for practice and not to be used in production.

json ./json

A customizable recursive descent parser for JSON. Based on the ECMA JSON standard.

Grammar

The following grammar syntax is based on the grammar syntax used in Crafting Interpreters.

value     ->  object | array | literal
object    ->  "{" property* "}"
array     ->  "[" value* "]"
property  ->  identifier ":" (object | literal) ","?
literal   ->  string | number | "true" | "false"| "null"

Options

The parser has some options for how it parses JSON.

pub struct Options {
    pub allow_unquoted_identifier: bool,
    pub allow_trailing_comma: bool,
    pub allow_single_quotes: bool,
    pub allow_comments: bool,
    pub tab_width: usize,
}

allow_unquoted_identifier

Allows keys in objects to be unquoted like is valid in JavaScript.

{
  foo: "bar"
}

allow_single_quotes

Allows single quotes like is valid in JavaScript.

{
  'foo': 'bar',
}

allow_trailing_comma

Allows trailing commas in objects and arrays.

{
  "foo": ["bar", "bar", "bar",],
}

allow_comments

Allows // and /**/ style comments.

{
  // foo bar
  "foo": "bar"
}

{
  /* foo bar */
  "foo": "bar"
}

Usage

Write your program.

use std::fs;

use json::parser::{error::Error, Options, Parser, Value};

fn main() -> Result<(), Error> {
    let source: String = fs::read_to_string("test.json").unwrap();

    let mut parser: Parser = Parser::new(Options::js());

    let result: Value =  parser.parse(source)?;

    dbg!(result);

    Ok(())
}

Add content to test.json.

/* Using Options::js() will allow this to be parsed normally */
{
    hello: 'world',
    things: ['one', 'two', 'three'],
}

Run to get the ast

cargo run