eslint-plugin-codegen

An eslint plugin for inline codegen. Auto-fixes out of sync code, with presets for barrels, jsdoc to markdown and more.

Motivation

Sometimes the same information is useful in multiple places - for example, jsdoc comments in code can double as markdown-formatted documentation for a library.

This allows generating code in a project using eslint, without having to incorporate any extra build tools, either for the codegen itself, or to validate that the generated code is up to date. So references to other parts of the project will always stay up to date - and your existing CI tools can enforce this just by running eslint.

Here's an example of it being used along with VSCode's eslint plugin, with auto-fix-on-save:

Contents

• Motivation
• Contents
• How to use
  • Setup
  • Presets
    • monorepoTOC
    • barrel
    • markdownFromJsdoc
    • markdownTOC
    • markdownFromTests
    • labeler
    • custom
  • Customisation

How to use

Setup

In an eslint-enabled project, install with

npm install --save-dev eslint-plugin-codegen

or

yarn add --dev eslint-plugin-codegen

Then add the plugin and rule to your eslint config, for example in eslintrc.js:

module.exports = {
  ...
  plugins: [
    ...
    'codegen'
  ],
  rules: {
    ...
    'codegen/codegen': 'error',
  },
}

You can use the rule by running eslint in a standard way, with something like this in an npm script: eslint --ext .ts,.js,.md .

In vscode, if using the eslint plugin, you may need to tell it to validate markdown files in your repo's .vscode/settings.json file (see this repo for an example):

{
  "eslint.validate": ["markdown", "javascript", "typescript"],
  "editor.codeActionsOnSave": {
    "source.fixAll.eslint": true
  }
}

To trigger the rule, add a comment line to a source file.

In markdown:

<!-- codegen:start {{ OPTIONS }} -->

In typescript/javascript:

// codegen:start {{ OPTIONS }}

Where {{ OPTIONS }} are an inline object in the format:

{preset: presetName, key1: value1, key2: value2}

Where key1 and key2 are options passed to the codegen preset. yaml is used to parse the object, So any valid yaml that fits on one line can be passed as options. In practise, the one-line restriction means using yaml's "flow style" for collections.

See below for documentation. This repo also has lots of usage examples.

Presets

monorepoTOC

Generate a table of contents for a monorepo.

Example (basic)

<!-- codegen:start {preset: monorepoTOC} -->

Example (using config options)

<!-- codegen:start {preset: monorepoTOC, repoRoot: .., workspaces: lerna, filter: {package.name: foo}, sort: -readme.length} -->

Params

Demo

barrel

Bundle several modules into a single convenient one.

Example

// codegen:start {preset: barrel, include: some/path/*.ts, exclude: some/path/*util.ts}
export * from './some/path/module-a'
export * from './some/path/module-b'
export * from './some/path/module-c'
// codegen:end

Params

Demo

markdownFromJsdoc

Convert jsdoc for an es export from a javascript/typescript file to markdown.

Example

<!-- codegen:start {preset: markdownFromJsdoc, source: src/foo.ts, export: bar} -->

Params

Demo

markdownTOC

Generate a table of contents from the current markdown file, based on markdown headers (e.g. ### My section title)

Example

<!-- codegen:start {preset: markdownTOC, minDepth: 2, maxDepth: 5} -->

Params

Demo

markdownFromTests

Use a test file to generate library usage documentation. Note: this has been tested with jest. It might also work fine with mocha, and maybe ava, but those haven't been tested.

Example

<!-- codegen:start {preset: markdownFromTests, source: test/foo.test.ts, headerLevel: 3} -->

Params

Demo

labeler

Generates a yaml config for the GitHub Pull Request Labeler Action. Creates a label per package name, which will be applied to any file modified under the leaf package path. When packages are added or removed from the repo, or renamed, the yaml config will stay in sync with them. Additional labels can be added outside of the generated code block. See https://github.com/mmkal/ts/tree/main/.github/labeler.yml for an example.

Example

# codegen:start {preset: labeler}

Note: eslint and related tools make it quite difficult to lint github action yaml files. To get it working, you'll need to:

• add '!.github' to your .eslintignore file, or the ignorePatterns property in your lint config.
• {vscode} add "yaml" to the "eslint.validate" list in vscode/settings.json.
• {@typescript/eslint} add '.yml' (and/or '.yaml') to the parserOptions.extraFileExtensions list in your lint config.
• {@typescript/eslint} explicitly include 'hidden' files (with paths starting with .) in your tsconfig. See https://github.com/mmkal/ts/tree/main/tsconfig.eslint.json for an example.

Params

Demo

custom

Define your own codegen function, which will receive all options specified. Import the Preset type from this library to define a strongly-typed preset function:

Example

import {Preset} from 'eslint-plugin-codegen'

export const jsonPrinter: Preset<{myCustomProp: string}> = ({meta, options}) => {
  const components = meta.glob('**\/*.tsx') // uses 'globSync' from glob package
  return `filename: ${meta.filename}\ncustom prop: ${options.myCustomProp}\nComponent paths: ${components.join(', ')}`
}

This can be used with:

<!-- codegen:start {preset: custom, source: ./lib/my-custom-preset.js, export: jsonPrinter, myCustomProp: hello} Note that a glob helper method is passed to the preset via meta. This uses the globSync method of https://npm.im/glob. There are also fs and path helpers passed, corresponding to those node modules respectively. These can be useful to allow access to those libraries without them being production dependencies.

Params

Demo

Note: right now, this preset isn't smart enough to follow source maps or transpile code, so source should point at compiled javascript, not typescript. And VSCode's eslint plugin caches modules, so if you edit the custom preset, you may need to recompile and reload VSCode for it to work properly.

Customisation

In addition to the custom preset, you can also define your own presets in eslint configuration, e.g.:

module.exports = {
  ...
  plugins: [
    ...
    'codegen'
  ],
  rules: {
    ...
    'codegen/codegen': [
      'error',
      {presets: require('./my-custom-presets')}
    ],
  },
}

presets should be a record of preset functions, conforming to the Preset interface from this package. This can be used to extend the in-built ones. For example, you could make generated markdown collapsible:

Before:

 <!-- codegen:start {preset: markdownTOC}-->
 - [Section1](#section1)
 - [Section2](#section2)
 <!-- codegen:end -->

my-custom-presets.js:

const {presets} = require('eslint-plugin-codegen')

module.exports.markdownTOC = (params) => {
  const toc = presets.markdownTOC(params)
  return [
    '<details>',
    '<summary>click to expand</summary>',
    '',
    toc,
    '</details>',
  ].join('\n')
}

.eslintrc.js:

module.exports = {
  ...
  plugins: [
    ...
    'codegen'
  ],
  rules: {
    ...
    'codegen/codegen': ['error', {presets: require('./my-custom-presets')}],
  },
}

After:

readme.md:

 <!-- codegen:start {preset: markdownTOC}-->
 <details>
  <summary>click to expand</summary>

 - [Section1](#section1)
 - [Section2](#section2)
 </details>
 <!-- codegen:end -->

Rendered:

The code in this repository was moved from https://github.com/mmkal/ts