jest-docblock

What is jest-docblock?

The jest-docblock package is used to parse and manipulate docblocks - comments at the top of a file that are often used to provide metadata about the file, such as descriptions, authors, and licenses. It is commonly used in the Jest testing framework to handle such metadata in test files.

What are jest-docblock's main functionalities?

Parsing docblocks

This feature allows you to parse the contents of a file to extract the metadata contained within a docblock. The parse function returns an object where each key is a tag from the docblock.

const { parse } = require('jest-docblock');
const contents = `/**
 * This is a docblock
 *
 * @flow
 */
const foo = 'bar';`;
const docblock = parse(contents);
console.log(docblock);

Extracting docblock

This feature allows you to extract the raw docblock as a string from the contents of a file. This can be useful if you want to manipulate the docblock as a whole or use it for documentation purposes.

const { extract } = require('jest-docblock');
const contents = `/**
 * This is a docblock
 *
 * @flow
 */
const foo = 'bar';`;
const docblockString = extract(contents);
console.log(docblockString);

Printing docblock

This feature allows you to take an object representing a docblock and print it back into the docblock format. This is useful for modifying or adding new metadata to a file's docblock.

const { print } = require('jest-docblock');
const docblock = { flow: '' };
const newContents = print(docblock);
console.log(newContents);

Other packages similar to jest-docblock

comment-parser

The comment-parser package is similar to jest-docblock in that it is used to parse comments in code. It supports parsing of block comments in various formats and is not tied to any specific testing framework, making it more flexible for different use cases.

doctrine

Doctrine is another JSDoc parsing library that can extract type information and other metadata from JSDoc comments. It is more focused on the JSDoc standard and provides a detailed AST of the parsed comments, which can be more powerful but also more complex than jest-docblock.

jsdoc-to-markdown

jsdoc-to-markdown is a package that takes JSDoc comments and converts them into markdown documentation. While it is not a direct alternative to jest-docblock, it serves a related purpose by transforming code comments into user-friendly documentation.

README

jest-docblock

jest-docblock is a package that can extract and parse a specially-formatted comment called a "docblock" at the top of a file.

A docblock looks like this:

/**
 * Stuff goes here!
 */

Docblocks can contain pragmas, which are words prefixed by @:

/**
 * Pragma incoming!
 *
 * @flow
 */

Pragmas can also take arguments:

/**
 * Check this out:
 *
 * @myPragma it is so cool
 */

jest-docblock can:

• extract the docblock from some code as a string
• parse a docblock string's pragmas into an object
• print an object and some comments back to a string

Installation

# with yarn
$ yarn add jest-docblock
# with npm
$ npm install jest-docblock

Usage

const code = `
/**
 * Everything is awesome!
 *
 * @everything is:awesome
 * @flow
 */

 export const everything = Object.create(null);
 export default function isAwesome(something) {
   return something === everything;
 }
`;

const {
  extract,
  strip,
  parse,
  parseWithComments,
  print,
} = require('jest-docblock');

const docblock = extract(code);
console.log(docblock); // "/**\n * Everything is awesome!\n * \n * @everything is:awesome\n * @flow\n */"

const stripped = strip(code);
console.log(stripped); // "export const everything = Object.create(null);\n export default function isAwesome(something) {\n return something === everything;\n }"

const pragmas = parse(docblock);
console.log(pragmas); // { everything: "is:awesome", flow: "" }

const parsed = parseWithComments(docblock);
console.log(parsed); // { comments: "Everything is awesome!", pragmas: { everything: "is:awesome", flow: "" } }

console.log(print({pragmas, comments: 'hi!'})); // /**\n * hi!\n *\n * @everything is:awesome\n * @flow\n */;

API Documentation

extract(contents: string): string

Extracts a docblock from some file contents. Returns the docblock contained in contents. If contents did not contain a docblock, it will return the empty string ("").

strip(contents: string): string

Strips the top docblock from a file and return the result. If a file does not have a docblock at the top, then return the file unchanged.

parse(docblock: string): {[key: string]: string | string[] }

Parses the pragmas in a docblock string into an object whose keys are the pragma tags and whose values are the arguments to those pragmas.

parseWithComments(docblock: string): { comments: string, pragmas: {[key: string]: string | string[]} }

Similar to parse except this method also returns the comments from the docblock. Useful when used with print().

print({ comments?: string, pragmas?: {[key: string]: string | string[]} }): string

Prints an object of key-value pairs back into a docblock. If comments are provided, they will be positioned on the top of the docblock.

Changelog

29.7.0

Features

• [create-jest] Add npm init / yarn create initialiser for Jest projects (#14465)
• [jest-validate] Allow deprecation warnings for unknown options (#14499)

Fixes

• [jest-resolver] Replace unmatched capture groups in moduleNameMapper with empty string instead of undefined (#14507)
• [jest-snapshot] Allow for strings as well as template literals in inline snapshots (#14465)
• [@jest/test-sequencer] Calculate test runtime if perStats.duration is missing (#14473)

Performance

• [@jest/create-cache-key-function] Cache access of NODE_ENV and BABEL_ENV (#14455)

Chore & Maintenance

• [jest-cli] Move internal config initialisation logic to the create-jest package (#14465)