shaharkazaz / optional-chaining-codemod

Codemod to migrate from Lodash get and logical and expressions to optional chaining

Optional chaining codemod

This is a codemod to migrate different types of lodash get calls and a && a.b kind of expressions to use optional chaining and nullish coalescing instead.

Following babel plugins are required to transpile optional chaining and nullish coalescing:

• babel-plugin-proposal-optional-chaining
• babel-plugin-proposal-nullish-coalescing-operator

What it does?

• a && a.b becomes a?.b
• _.get(foo, 'a.b') and _.get(foo, ['a', 'b']) becomes foo?.a?.b
• _.get(foo, 'a.b', defaultValue) becomes foo?.a?.b ?? defaultValue

You can check out the __textfixtures__ folder to see full list of supported transformations.

Why should I migrate to use optional chaining?

• When using static type checkers like Flow, optional chaining provides much better type safety than lodash get. However, optional chaining is not only Flow feature but you can use it with babel already today.
• It also has a neater syntax than chaining && expressions one after another.

Install

$ yarn global add optional-chaining-codemod

or

$ npm install -g optional-chaining-codemod

Usage

$ optional-chaining-codemod ./**/*.js

with flow parser:

$ optional-chaining-codemod ./**/*.js --parser=flow

with typescript parser:

$ optional-chaining-codemod ./**/*.ts --parser=ts

The CLI is the same as in jscodeshift except you can omit the transform file.

Alternatively, you can run the codemod using jscodeshift as follows:

$ yarn global add jscodeshift
$ yarn add optional-chaining-codemod
$ jscodeshift -t node_modules/optional-chaining-codemod/transform.js ./**/*.js

flags

This codemod has two flags:

1. --skipVariables to skip variables passed to lodash get
2. --skipTemplateStrings to skip template strings passed to lodash get

Especially the first case is risky as the variable might actually be something like var bar = "a.b.c" and produce from _.get(foo, bar) following: foo?[bar] although lodash would treat it like foo?.a?.b?.c".

Contributing

Contributions are more than welcome! One area of improvement could be e.g better CLI or finding out new areas to migrate to use optional chaining.