jsdoc-type-pratt-parser

This project is a parser for jsdoc types. It is heavily inspired by the existing libraries catharsis and jsdoctypeparser, but does not use PEG.js, instead it is written as a pratt parser.

• https://github.com/hegemonic/catharsis
• https://github.com/jsdoctypeparser/jsdoctypeparser
• http://journal.stuffwithstuff.com/2011/03/19/pratt-parsers-expression-parsing-made-easy/

Live Demo

A simple live demo to test expressions can be found at: https://jsdoc-type-pratt-parser.github.io/jsdoc-type-pratt-parser/

Getting started

npm install jsdoc-type-pratt-parser@alpha

import { parse } from 'jsdoc-type-pratt-parser'

const result = parse('myType.<string>', 'closure')

This library supports compatibility modes for catharsis and jsdoctypeparser. The provided transform functions attempt to transform the output to the expected output of the target library. This will not always be the same as some types are parsed differently. These modes are thought to make transition easier, but it is advised to use the native output as this will be more uniform and will contain more information.

Catharsis compat mode:

import { parse, catharsisTransform } from 'jsdoc-type-pratt-parser'

const result = catharsisTransform(parse('myType.<string>', 'closure'))

Jsdoctypeparser compat mode:

import { parse, jtpTransform } from 'jsdoc-type-pratt-parser'

const result = jtpTransform(parse('myType.<string>', 'closure'))

Stringify:

import { stringify } from 'jsdoc-type-pratt-parser'

const val = stringify({ type: 'JsdocTypeName', value: 'name'}) // -> 'name'

You can customize the stringification by using stringifyRules and transform:

import { stringifyRules, transform } from 'jsdoc-type-pratt-parser'

const rules = stringifyRules()

// `result` is the current node and `transform` is a function to transform child nodes.
rules.NAME = (result, transform) => 'something else'

const val = transform(rules, { type: 'JsdocTypeName', value: 'name'}) // -> 'something else'

You can traverse a result tree with the traverse function:

import { traverse } from 'jsdoc-type-pratt-parser'

// property is the name of the property on parent that contains node
function onEnter(node, parent, property) {
    console.log(node.type)
}

// an onEnter and/or an onLeave function can be supplied
traverse({ type: 'JsdocTypeName', value: 'name'}, onEnter, console.log)

You can also build your own transform rules by implementing the TransformRules<TransformResultType> interface or you can build upon the identity ruleset like this:

import { identityTransformRules, transform } from 'jsdoc-type-pratt-parser'

const myRules = identityTransformRules()
myRules.NAME = () => ({ type: 'JsdocTypeName', value: 'funky' })

const val = transform(myRules, result)

Available Grammars

Three different modes (grammars) are supported: 'jsdoc', 'closure' and 'typescript'

Tests Status

This parser runs most tests of https://github.com/hegemonic/catharsis and https://github.com/jsdoctypeparser/jsdoctypeparser. It compares the results of the different parsing libraries. If you want to find out where the output differs, look in the tests for the comments // This seems to be an error of ... or the differ keyword which indicates that differing results are produced.

API Documentation

An API documentation can be found here: https://jsdoc-type-pratt-parser.github.io/jsdoc-type-pratt-parser/docs/modules.html

Performance

A simple performance comparision using Benchmark.js produced the following results:

Testing expression: Name
catharsis x 36,338 ops/sec ±1.10% (1071 runs sampled)
jsdoc-type-pratt-parser x 400,260 ops/sec ±0.87% (1070 runs sampled)
jsdoctypeparser x 61,847 ops/sec ±1.18% (1071 runs sampled)
The fastest was jsdoc-type-pratt-parser

Testing expression: Array<number>
catharsis x 7,969 ops/sec ±1.05% (1079 runs sampled)
jsdoc-type-pratt-parser x 159,001 ops/sec ±0.95% (1074 runs sampled)
jsdoctypeparser x 42,278 ops/sec ±1.01% (1070 runs sampled)
The fastest was jsdoc-type-pratt-parser

Testing expression: { keyA: Type<A | "string val" >, keyB: function(string, B): A }
catharsis x 933 ops/sec ±1.15% (1070 runs sampled)
jsdoc-type-pratt-parser x 29,596 ops/sec ±0.90% (1068 runs sampled)
jsdoctypeparser x 16,206 ops/sec ±1.38% (1055 runs sampled)
The fastest was jsdoc-type-pratt-parser

the test uses catharsis without cache, as this is just a simple lookup table that could easily be implemented for any parser.

Changelog

1.2.0 (2021-10-02)

Features

• parser: add readonly modifier for object properties (ad3f0c9)