JSON5 parser and stringifier for MoonBit

json

json5

Author

tiye

Version

0.0.3

License

Apache-2.0

Repository

github.com/worktools/json5.mbt

Last updated

5 months ago

Downloads

No dependencies

#tiye/json5

This document was generated with AI assistance and then reviewed/edited for this project. Contributions are welcome via PRs, and AI-assisted review may be used during the review process.

A lightweight JSON5 parser/serializer for MoonBit.

This package lets you parse JSON5 input (comments, trailing commas, single-quoted strings, unquoted keys, hex numbers, Infinity, NaN) and work with either:

Json5Value (package-native value tree), or
core Json (via helper APIs and traits).

#Features

Parse JSON5 object/array/value syntax
Support line comments // ... and block comments /* ... */
Support trailing commas in objects and arrays
Support unquoted object keys (identifier style)
Support single-quoted strings
Support number forms: decimal, exponent, hex (0x10), Infinity, NaN
Convert between Json5Value and core Json using ToJson / FromJson

#Installation

Add this package to your MoonBit module dependencies (according to your workspace setup), then import and use:

///|
let value = @json5.parse("{foo: 'bar'}")

#Quick Start

#Parse to Json5Value

///|
test "readme parse json5 value" {
  let value = @json5.parse("{foo: 'bar', nums: [1, 2,],}")
  guard value is @json5.Object(obj)
  assert_true(obj.get("foo") is Some(_))
}

#Stringify from Json5Value

///|
test "readme stringify json5 value" {
  let value = @json5.parse("{ok: true}")
  let text = @json5.stringify(value)
  // valid identifiers are written unquoted in JSON5
  assert_true(text.contains("ok:true"))
}

#Parse directly to core Json

///|
test "readme parse json5 to json" {
  let json = @json5.parse_json("{foo: [1, true, 'x']}")
  @json.json_inspect(json, content={ "foo": [1, true, "x"] })
}

#Stringify from core Json

///|
test "readme stringify json" {
  let text = @json5.stringify_json({ "name": "moonbit", "v": 1 })
  // valid identifiers are written unquoted in JSON5
  assert_true(text.contains("name:\"moonbit\""))
}

#Public API

parse(input : String) -> Json5Value raise Error
parse_json(input : String) -> Json raise Error
stringify(val : Json5Value) -> String
stringify_json(json : Json) -> String raise @json.JsonDecodeError

Types:

pub enum Json5Value { Null | True | False | Number(Double) | String(String) | Array(Array[Json5Value]) | Object(Map[String, Json5Value]) }

Traits:

impl ToJson for Json5Value
impl @json.FromJson for Json5Value

#Error Handling

parse / parse_json raise Error for malformed JSON5 text.
stringify_json raises @json.JsonDecodeError if conversion from core Json to Json5Value fails.

Use try/catch when you need resilient decoding.

#Current Limitations

Unicode escape in strings (\uXXXX) is not implemented yet.
Serializer currently outputs compact text only (no pretty formatting mode).

#Tests

Run:

moon test

Json5Value

source

pub enum Json5Value {
  Null
  True
  False
  Number(Double)
  String(String)
  Array(Array[Json5Value])
  Object(Map[String, Json5Value])
} derive(Eq, @moonbitlang/core/debug.Debug
Debug)

Represents a JSON5 value tree.

This enum is the primary data model for parsed JSON5 content in this package. It mirrors regular JSON shapes while preserving JSON5-friendly numeric forms during parsing (for example NaN and Infinity).

Variants:

Null
True
False
Number(Double)
String(String)
Array(Array[Json5Value])
Object(Map[String, Json5Value])

Example:

test {
  let value = @json5.parse("{foo: [1, true, 'x']}")
  guard value is Object(obj)
  assert_true(obj.get("foo") is Some(Array(_)))
}

impl Show for Json5Value

impl ToJson for Json5Value

fn to_json(self : Json5Value) -> Json

source

Converts Json5Value to core Json.

This is useful when you want to parse with JSON5 syntax and then operate with MoonBit's standard @json ecosystem.

Notes:

NaN and infinities are delegated to Double::to_json behavior.
Object key order follows the underlying map iteration order.

impl FromJson for Json5Value

fn from_json(json : Json, path : @moonbitlang/core/json.JsonPath
JsonPath) -> Json5Value raise @moonbitlang/core/json.JsonDecodeError
JsonDecodeError

source

Converts core Json to Json5Value.

This implementation is recursive and propagates JSON path information to nested conversions, making decode errors easier to locate.

Typical usage:

test {
  let json : Json = { "name": "moonbit", "ok": true }
  let value : @json5.Json5Value = @json.from_json(json)
  guard value is Object(obj)
  assert_true(obj.get("name") is Some(_))
}

parse

source

fn parse(input : String) -> Json5Value raise

Parses a JSON5 text into Json5Value.

This is the primary entry point for JSON5 parsing in this package.

Raises Error for malformed input.

Example:

test {
  let value = @json5.parse("{foo: 'bar', nums: [1, 2,],}")
  guard value is Object(obj)
  assert_true(obj.get("foo") is Some(_))
}

parse_json

source

fn parse_json(input : String) -> Json raise

Parses JSON5 text directly into core Json.

This helper is convenient when your downstream code already uses @json APIs and you do not need to manually inspect Json5Value.

Equivalent to:

parse(input).to_json()

stringify

source

fn stringify(val : Json5Value) -> String

Serializes Json5Value to compact text.

Object keys that are valid JSON5 identifiers are written unquoted; all other keys are quoted.

Number behavior:

finite numbers: normal decimal formatting
NaN: "NaN"
positive infinity: "Infinity"
negative infinity: "-Infinity"

Example:

test {
  let value = @json5.parse("{foo: 'bar'}")
  let text = @json5.stringify(value)
  assert_true(text.contains("foo:\"bar\""))
}

stringify_json

source

fn stringify_json(json : Json) -> String

Serializes core Json to compact JSON5 text.

Object keys that are valid JSON5 identifiers are written unquoted.

stringify_json_pretty

source

fn stringify_json_pretty(json : Json, indent_size? : Int) -> String

Serializes core Json to a pretty-printed JSON5 string.

Convenience wrapper around stringify_pretty that converts Json first. The indent_size labeled argument defaults to 2.

stringify_pretty

source

fn stringify_pretty(val : Json5Value, indent_size? : Int) -> String

Serializes Json5Value to a pretty-printed JSON5 string.

Object keys that are valid JSON5 identifiers are written unquoted. The indent_size labeled argument controls indentation spaces per level and defaults to 2.

Example:

test {
  let value = @json5.parse("{foo: [1, true]}")
  let text = @json5.stringify_pretty(value)
  assert_true(text.contains("foo: [\n"))
}

Source Files

json5.mbt

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json5

#tiye/json5

#Features

#Installation

#Quick Start

#Parse to Json5Value

#Stringify from Json5Value

#Parse directly to core Json

#Stringify from core Json

#Public API

#Error Handling

#Current Limitations

#Tests

#Json5Value

#parse

#parse_json

#stringify

#stringify_json

#stringify_json_pretty

#stringify_pretty

Source Files

Json5Value

parse

parse_json

stringify

stringify_json

stringify_json_pretty

stringify_pretty