airbnb-to-eslintrc

Consolidates a Javascript style guide (for example the popular style guide provided by Airbnb) into a single eslintrc.json file with no references to 'extended' style guide files in node_modules.

The main purpose is to prevent cluttering of dependencies of small projects. The index.js file will read a base .eslintrc or eslintrc.json file, and recursively load all eslint configuration files referred to by extends directives anywhere in the chain. The resulting eslintrc.json file can be installed in the user's home directory and will automatically be used by eslint without having to install, for example eslint-config-airbnb (with dozens of further dependencies) in each project, large or small.

It is possible to obtain the current eslint configuration directly from eslint, by using the command node_modules/eslint/bin/eslint.js --print-config .. However, the rules gathered by using this command includes all rules found in all configuration files in the 'extends' chain, which includes rules that are used by various eslint plugins (regardless if those plugins are defined in the top level .eslintrc file or not). The index.js file in this project, on the other hand, only includes those rules that are used by those plugins defined in the top level eslintrc file, and those rules that are not used by any plugins.

Furthermore, the eslint command listed above does not always properly convert the rules in the eslint configuration files (which are JSON-like structures) found in the 'extends' chain to proper rules. For example, if the plugin 'import' is defined in the top level eslintrc file, then the property maxDepth (which is set to the value Infinity, an illegal JSON value) will be converted to null, which results in a subsequent load error. The index.js in this project will convert such value to Number.MAX_SAFE_INTEGER.

The project demonstrates several modern Javascript features such as

• Using async/await when following the 'extends' chain
• Using dynamic import of modules

To use, follow these steps:

1. Make sure eslint is installed, either globally or locally (in a development directory). In this project, eslint version 5.7.0 has been used (earlier version may work as well). Do eslint --version to get the version
2. Then make sure that eslint actually works from the command line and from any installed editor plugins – if it doesn't, none of steps below will matter
3. Clone this repo
4. Navigate to the cloned directory
5. Edit the initial (and hidden) .eslintrc.json if needed. The file contains a few overrides of the Airbnb's style rules, which you may or may not like. Most likely you'll want to add your own overrides. Or start from a completly fresh barebones eslint configuration by issuing the command eslint --init and follow the prompts
6. Install the Airbnb style guide with npm install
7. Ensure that you're using a modern version of node. Verify node version with node --version. In this project, node version 10.12.0 has been used (earlier versions may work as well)
8. To generate the single lint configuration file, do node --experimental-modules index
9. The file produced will be called eslintrc.json (please note the file name, it is not hidden, and therefore will not overwrite the existing .eslintrc.json)
10. To use the just-created eslintrc.json file, copy it to another project directory, or anywhere in the file system (for example your home directory (~). Then rename the file to .eslintrc.json (please note the '.' as first character, which makes the file name findable by eslint and also hidden). Eslint and related plugins will search for this file in the current directory, and if not found, will attempt to find the file higher in the hierarchy

Example output from the index.js script

Found .eslintrc file: .eslintrc.json
Found no top level plugins
Recursing into airbnb-to-eslintrc/.eslintrc.json
Recursing into airbnb-to-eslintrc/node_modules/eslint-config-airbnb/.eslintrc
Recursing into airbnb-to-eslintrc/node_modules/eslint-config-airbnb/index.js
Recursing into airbnb-to-eslintrc/node_modules/eslint-config-airbnb-base/index.js
Recursing into airbnb-to-eslintrc/node_modules/eslint-config-airbnb-base/rules/best-practices.js
Recursing into airbnb-to-eslintrc/node_modules/eslint-config-airbnb-base/rules/errors.js
Recursing into airbnb-to-eslintrc/node_modules/eslint-config-airbnb-base/rules/node.js
Recursing into airbnb-to-eslintrc/node_modules/eslint-config-airbnb-base/rules/style.js
Recursing into airbnb-to-eslintrc/node_modules/eslint-config-airbnb-base/rules/variables.js
Recursing into airbnb-to-eslintrc/node_modules/eslint-config-airbnb-base/rules/es6.js
Recursing into airbnb-to-eslintrc/node_modules/eslint-config-airbnb-base/rules/imports.js
Recursing into airbnb-to-eslintrc/node_modules/eslint-config-airbnb-base/rules/strict.js
Recursing into airbnb-to-eslintrc/node_modules/eslint-config-airbnb/rules/react.js
Recursing into airbnb-to-eslintrc/node_modules/eslint-config-airbnb/rules/react-a11y.js

...

Found duplicate rule:  [no-plusplus]
  Existing rule value: "error"
  New rule value:      ["error",{"allowForLoopAfterthoughts":true}]
  From file:           airbnb-to-eslintrc/.eslintrc.json

Found duplicate rule:  [linebreak-style]
  Existing rule value: ["error","unix"]
  New rule value:      ["error","unix"]
  From file:           airbnb-to-eslintrc/.eslintrc.json

Found duplicate rule:  [quotes]
  Existing rule value: ["error","single",{"avoidEscape":true}]
  New rule value:      ["error","single"]
  From file:           airbnb-to-eslintrc/.eslintrc.json
...

Wrote 273 rules to eslintrc.json

countRules utility

The utility countRules.js is found in the util directory, and can be used to list the number of rules in a eslintrc file. Invoke it like so: node util/countRules eslintrc-file --list-rules. It produces an output like this:

Found 263 eslint rules in eslintrc-output-example.json

Found these top level properties:
env
parser
parserOptions
plugins
rules

Found these rules:
accessor-pairs
array-bracket-newline
array-bracket-spacing
array-callback-return
array-element-newline
...
template-tag-spacing
unicode-bom
use-isnan
valid-jsdoc
valid-typeof
vars-on-top
wrap-iife
wrap-regex
yield-star-spacing
yoda

Miscellaneous commands

• Obtain current rule configuration of the .eslintrc file (including all 'extended' rule sets): node_modules/eslint/bin/eslint.js --print-config .
• Obtain rule configuration after running index.js: node_modules/eslint/bin/eslint.js --no-eslintrc --config eslintrc.json --print-config .