lezer-json5

library2.0.2jsnpmunverified

lezer-json5 is a Lezer grammar designed for parsing JSON5 (JavaScript Object Notation, Fifth Edition) syntax. JSON5 extends standard JSON by adding features like comments, unquoted object keys, trailing commas, and single-quoted strings, making configuration files more human-readable. This package, currently at version 2.0.2, integrates seamlessly with CodeMirror 6, providing robust syntax highlighting and language-aware editing capabilities for JSON5 documents. While the package was last published three years ago, it remains a stable and functional solution for JSON5 parsing within the Lezer/CodeMirror ecosystem, leveraging principles from the official Lezer JavaScript grammar. Its slow release cadence suggests a mature grammar that is unlikely to require frequent updates unless core Lezer APIs or the JSON5 specification undergo significant changes. It differentiates itself by offering incremental parsing specific to the JSON5 specification, which is crucial for performance in large editor instances.

serialization

npm install lezer-json5

github ↗package ↗

INSTALL

IMPORT

SIG · LEZER-JSON5

lezer-json5

serializationjavascriptv2.0.2

Install

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Import

—

Disk

—

Pass rate

0/ 6

Env Coverage0 / 6

glibc

18–22

musl

18–22

Install & Compatibility

Where this runs

tested against v? · npm install

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

node 18–226 runs

build_error

glibc

node 18–226 runs

build_error

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

json5

✓ import { json5 } from 'lezer-json5';

✗ const json5 = require('lezer-json5');

This package is designed for modern ESM environments, especially with CodeMirror 6.

json5

✓ import { json5 } from 'lezer-json5';

✗ import json5 from 'lezer-json5';

The parser is a named export, not a default export.

LanguageSupport

✓ import { LanguageSupport } from '@codemirror/language';

Required to integrate the Lezer parser with CodeMirror 6 as a language extension.

Demonstrates setting up a basic CodeMirror 6 editor with `lezer-json5` for syntax highlighting and language support for JSON5 documents.

import { EditorState } from '@codemirror/state'; import { EditorView, basicSetup } from 'codemirror'; import { json5 } from 'lezer-json5'; import { LanguageSupport } from '@codemirror/language'; const json5Doc = ` // This is a JSON5 document { key: "value", // Unquoted keys and comments are allowed anotherKey: [ 1, 2, // Trailing commas are fine 3, ], "quoted-key": 0xAF, // Hexadecimal numbers lastValue: .5e-2, // Leading/trailing decimal points, exponential notation true, false, null, } `; const state = EditorState.create({ doc: json5Doc, extensions: [ basicSetup, // Provides essential editor functionality (line numbers, history etc.) new LanguageSupport(json5()), // Activates JSON5 syntax highlighting and language features ], }); const editorParent = document.createElement('div'); document.body.appendChild(editorParent); new EditorView({ state, parent: editorParent, }); console.log('CodeMirror 6 editor with JSON5 support initialized.');

Debug

Known issues

breakingBreaking changes in core Lezer packages (`@lezer/common`, `@lezer/lr`) or CodeMirror 6 major versions can potentially impact `lezer-json5` functionality, requiring updates to maintain compatibility. Users should consult the Lezer and CodeMirror changelogs.

fix

Ensure your `@lezer/*` and `codemirror` packages are compatible with the `lezer-json5` version, typically by updating to the latest stable versions of all related CodeMirror/Lezer packages.

affects: >=1.0.0

gotchaJSON5 is a superset of JSON. Attempting to parse JSON5 content with a standard JSON parser (e.g., `lezer-json` or `JSON.parse`) will result in syntax errors for valid JSON5 features like comments, unquoted keys, or trailing commas.

fix

Always use the `lezer-json5` parser for JSON5 content. Do not substitute with a plain JSON parser if JSON5 features are present.

affects: >=1.0.0

gotchaThe package has not been updated in approximately three years. While it indicates stability, it also means that very recent changes to the JSON5 specification (if any) or major advancements in the Lezer parsing system might not be immediately incorporated.

fix

For mission-critical applications or if you require the absolute latest JSON5 features, review the GitHub repository for any unreleased updates or forks. Otherwise, assume the current feature set is stable.

affects: >=1.0.0

Errors

Common errors & fixes

SyntaxError: Cannot use import statement outside a module

Attempting to use `import` syntax in a CommonJS (`require`) environment without proper transpilation or Node.js ESM configuration.

fix

Ensure your project is configured for ESM (e.g., `"type": "module"` in `package.json`) or use a bundler like Webpack/Rollup/ESBuild that transpiles ESM imports for your target environment. This package is ESM-first.

TypeError: (0, _lezer_json5__WEBPACK_IMPORTED_MODULE_2__.json5) is not a function

Incorrectly importing the `json5` parser. It is usually a function that needs to be called to create the language extension for CodeMirror.

fix

Ensure you call the `json5` function when providing it to `LanguageSupport`: `new LanguageSupport(json5())`.

Property 'json5' does not exist on type 'typeof import("lezer-json5")'

Potentially using an outdated TypeScript version, incorrect `tsconfig.json` settings, or a bundler that mishandles module resolution, leading to type declaration issues.

fix

Verify that your TypeScript version is up-to-date and your `tsconfig.json` has `"moduleResolution": "Bundler"` or `"NodeNext"` (depending on your setup) and `"module": "ESNext"` or similar settings that correctly resolve ESM type declarations.

Upgrade

Version history

2.0.2latest on npm

Audit

Dependencies

@lezer/lrrequiredRuntime dependency for the generated Lezer LR parser.

Agent activity

2 hits · last 30 days

node

Resources

githubhttps://github.com/dimfeld/lezer-json5 ↗

packagehttps://www.npmjs.com/package/lezer-json5 ↗