JHON Language Support

JHON === JinHui's Object Notation — a configuration language with key=value syntax, comments, raw strings, and flexible separators.

Overview

This VSCode extension provides syntax highlighting, formatting, and live diagnostics for JHON files (.jhon). The parser is the canonical TypeScript implementation at @zjhken/jhon, mirrored from the Rust reference — see ../SPEC.md for the language spec.

Features

• Syntax highlighting for JHON: comments, strings (including raw strings), numbers (decimal, hex, octal, binary, exponents), booleans, null, nested objects and arrays
• Document and range formatting (Shift+Alt+F) that preserves your comments through round-trips
• Live diagnostics — red squiggles under spec violations as you type, with entries in the Problems panel
• "Format to One Line" command that collapses the document to compact JHON
• Strict spec compliance — every rule in SPEC §8 is enforced, so malformed input is reported immediately

JHON syntax example

// Application configuration
app_name = "ocean-note"
version = "1.0.0"

// Feature flags
features = ["markdown", "collaboration", "real-time"]

// Database configuration
database = {
  host = "localhost"
  port = 5432
  name = "mydb"
  credentials = [
    { user = "admin", role = "owner" }
    { user = "reader", role = "readonly" }
  ]
}

max_file_size = 1_048_576
timeout = 30.5
debug = true
log_level = "info"

A JHON document doesn't have to be an object. If the first top-level element is anything other than a key=value pair, the whole document is treated as an array (with the surrounding [] omitted):

// Array-mode document
1
2
"haha"
{a=4}
// → [1, 2, "haha", {"a": 4}]

An empty document (empty string, whitespace-only, or comments-only) parses to null.

Key rules (per SPEC.md)

1. Separators are commas OR newlines — two items on the same line require a comma (SPEC §5.3). Spaces alone between items are an error.
2. Comments — // line comments and /* */ block comments (non-nesting). May appear anywhere whitespace is allowed.
3. Strings — double or single quoted, with escapes \n \t \r \b \f \" \' \\ \/ \uXXXX \xXX. Unknown escapes are errors. Literal control characters are forbidden.
4. Raw strings — Rust-style r"..." / R"..." with optional # delimiters (r#"..."#, r##"..."##). No escape processing. May span multiple lines.
5. Numbers — decimal (42, 1_000_000), hex (0xff), octal (0o777), binary (0b1010), floats (3.14, 1.5e-3). Underscores allowed between digits only. Radix prefixes are lowercase only.
6. Keys — bare identifiers may contain any character except whitespace, =, ,, { } [ ], /, " ', and #. Unicode letters, digits, hyphens, dots, and emoji are all valid in any position.
7. Top-level — object mode (a sequence of key=value pairs, braces optional) or array mode (any sequence of bare values; the surrounding [] is implicit). The first top-level element decides the mode; mixing pairs and bare values is an error. Top-level {...} and [...] are always single elements of the implicit array, never document wrappers. Empty input parses to null.
8. Duplicate keys in the same object are an error.

Raw string examples

// Simple raw string
simple = r"Hello, World!"

// Raw string containing quotes
with_quotes = r#"He said "Hello" to me"#

// Multi-line raw string
multiline = r#"This is a
multi-line
string without escaping"#

// Raw string with special characters
path = r"C:\Users\name\file.txt"
regex = r"\d+\w+\s+"

Installation

From VSCode Marketplace

Search for "JHON Language Support" in the VSCode extensions panel.

Manual installation

1. Download the latest .vsix from the Releases page
2. Open VSCode → Extensions panel → "..." menu → "Install from VSIX..."
3. Select the downloaded file

Usage

Create a file with the .jhon extension. The extension automatically activates and provides highlighting, formatting, and diagnostics.

Formatter

The formatter wraps the canonical @zjhken/jhon parser/serializer. It produces pretty output per SPEC §7.1: multi-line, spaces around =, newline-only separators (no commas), no trailing commas. The formatter handles both object-mode and array-mode documents (per SPEC §2) — array-mode documents format as one element per line with no surrounding [].

Formatting features

• Document formatting: Format Document (Shift+Alt+F on Windows/Linux, Shift+Option+F on Mac)
• Range formatting: Format Selection on the highlighted region
• Format on save: enable via VSCode's editor.formatOnSave setting

Compact format command

The "JHON: Format to One Line" command (Command Palette) collapses the entire document into compact JHON — single line, no spaces around =, no spaces after commas, no trailing commas.

Configuration

Customize the formatter in settings.json:

{
  // Enable/disable the JHON formatter (default: true)
  "jhon.format.enable": true,

  // Use spaces for indentation vs. tabs (default: false → tabs)
  "jhon.format.insertSpaces": false,

  // Number of spaces per indent level when insertSpaces is true,
  // or visual size of one tab (default: 2)
  "jhon.format.tabSize": 2,

  // Sort object keys alphabetically on serialize.
  // Default false — SPEC §5.4 mandates insertion order.
  "jhon.format.sortKeys": false,

  // Enable live parse-error diagnostics (default: true)
  "jhon.diagnostics.enable": true,

  // Debounce window (ms) after a keystroke before re-parsing (default: 300)
  "jhon.diagnostics.debounceMs": 300
}

Formatter example

Input (compact, key order scrambled):

debug=true,version="1.0.0",app_name="ocean-note",database={name="mydb",port=5432,host="localhost"},features=["markdown","collaboration","real-time"]

After "Format Document" (default settings — preserves insertion order, no commas):

debug = true
version = "1.0.0"
app_name = "ocean-note"
database = {
  name = "mydb"
  port = 5432
  host = "localhost"
}
features = [
  "markdown"
  "collaboration"
  "real-time"
]

After "JHON: Format to One Line":

debug=true,version="1.0.0",app_name="ocean-note",database={name="mydb",port=5432,host="localhost"},features=["markdown","collaboration","real-time"]

Diagnostics

When jhon.diagnostics.enable is true, the extension parses the document live (debounced by jhon.diagnostics.debounceMs ms after the last keystroke, and on save). Any SPEC.md violation produces a red squiggle and an entry in the Problems panel:

• Top-level scalars (42, "foo", true, null alone)
• Same-line items without a comma (a=1 b=2)
• Malformed numbers (+5, 0Xff, 5u8, 5_, _5, 5__5)
• Duplicate keys
• Unknown escapes ("foo\q")
• Literal control chars in strings
• Unterminated strings, raw strings, comments, arrays, objects
• Unbalanced braces/brackets
• Empty keys
• Top-level array followed by other content

The diagnostic source is labeled jhon, and the range reflects the offending token's source position.

File association

.jhon files are automatically associated with the JHON language.

License

MIT. See LICENSE for the full text.

Contributing

Contributions are welcome — please open a Pull Request at github.com/zjhken/jhon.

Author

Jinhui ZHANG — GitHub