@peterczg/babel-plugin-transform-imports

babel-plugin-transform-imports

A fork of babel-plugin-transform-imports introduced enhanced transform function for customization.

What's New?

Suppose there are Row, Col, Layout three components in react-bootstrap lib/Layout, and Layout is the default export while the others are member exports

 import { Layout, Row, Col } in 'react-bootstrap'

It will generate something as follow:

import Layout from 'react-bootstrap/lib/Layout'
import { Row } from 'react-bootstrap/lib/Layout'
import { Col } from 'react-bootstrap/lib/Layout'

And you just need to write the transform function like this:

babel.config.js:

module.exports = {
  "plugins": [
    ["@peterczg/babel-plugin-transform-imports", {
      "react-bootstrap": {
        "transform": (importName) => {

          if(importName === 'Layout') 
          return { 
            default: true, 
            replace: 'react-bootstrap/lib/Layout'
          }

          if(importName === 'Row' || importName === 'Col') 
          return { 
            default: false, 
            replace: `react-bootstrap/lib/${importName}` 
          }
          
          return `react-bootstrap/lib/${importName}`
        },
        "style": (importName, importPath) => {
          return `react-bootstrap/style/${importName}.css`
        },
        "preventFullImport": true
      },
    }]
  ]
}

So now the transform function can return either string or an object whose shape is like

type TransformReturnType = string | {
  /* import path */
  replace: string
  /* 
   * whether it is the default export or not(member export)
   * @default false
   */
  default?: boolean
}

Fomer Doc

Transforms member style imports:

import { Row, Grid as MyGrid } from 'react-bootstrap';
import { merge } from 'lodash';

...into default style imports:

import Row from 'react-bootstrap/lib/Row';
import MyGrid from 'react-bootstrap/lib/Grid';
import merge from 'lodash/merge';

Note: this plugin is not restricted to the react-bootstrap and lodash libraries. You may use it with any library.

Why?

When Babel encounters a member style import such as:

import { Grid, Row, Col } from 'react-bootstrap';

it will generate something similarish to:

var reactBootstrap = require('react-bootstrap');
var Grid = reactBootstrap.Grid;
var Row = reactBootstrap.Row;
var Col = reactBootstrap.Col;

Which causes the entire library to be loaded, even though only some components are needed. Some libraries are rather large and pulling in the entire module would cause unnecessary bloat to your client optimized (webpack etc.) bundle. The only way around this is to use default style imports:

import Grid from 'react-bootstrap/lib/Grid';
import Row from 'react-bootstrap/lib/Row';
import Col from 'react-bootstrap/lib/Col';

But, the more pieces we need, the more this sucks. This plugin will allow you to pull in just the pieces you need, without a separate import for each item. Additionally, it can be configured to throw when somebody accidentally writes an import which would cause the entire module to resolve, such as:

import Bootstrap, { Grid } from 'react-bootstrap';
// -- or --
import * as Bootstrap from 'react-bootstrap';

Installation

npm install --save-dev babel-plugin-transform-imports

Usage

.babelrc:

{
  "plugins": [
    ["@peterczg/babel-plugin-transform-imports", {
      "react-bootstrap": {
        "transform": "react-bootstrap/lib/${member}",
        "preventFullImport": true
      },
      "lodash": {
        "transform": "lodash/${member}",
        "preventFullImport": true
      }
    }]
  ]
}

Advanced Transformations

Using regular expressions

Sometimes, you may wish to use regular expressions in your transformation (for example, to enforce the same convention in all folder levels on the structure of your library).

.babelrc:

{
  "plugins": [
    ["@peterczg/babel-plugin-transform-imports", {
      "my-library\/?(((\\w*)?\/?)*)": {
        "transform": "my-library/${1}/${member}",
        "preventFullImport": true
      }
    }]
  ]
}

Causes this code:

import { MyModule } from 'my-library';
import { App } from 'my-library/components';
import { Header, Footer } from 'my-library/components/App';

to become:

import MyModule from 'my-library/MyModule';
import App from 'my-library/components/App';
import Header from 'my-library/components/App/Header';
import Footer from 'my-library/components/App/Footer';

Using a function as the transformer

If you need more advanced or more specific transformation logic, and are using Babel 7+ with a babel.config.js file, you may provide a function instead of a string for the transform option:

babel.config.js:

module.exports = {
  presets: ['@babel/env'],
  plugins: [
    ['@peterczg/babel-plugin-transform-imports', {
      'my-library': {
        transform: (importName, matches) => `my-library/etc/${importName.toUpperCase()}`,
        preventFullImport: true,
      },
      'date-fns': {
        transform: importName => `date-fns/${camelCase(importName)}`,
        preventFullImport: true,
      },
    }]
  ]
};

You may combine a regular expression in the library name with a function transform, and any captures of the regex will be passed as a second argument.

Webpack

This can be used as a plugin with babel-loader.

webpack.config.js:

module: {
  rules: [{
    test: /\.js$/,
    exclude: /(node_modules|bower_components)/,
    use: {
      loader: 'babel-loader',
      query: {
        plugins: [
          [require('babel-plugin-transform-imports'), {
            'my-library': {
              transform: function(importName, matches) {
                return 'my-library/etc/' + importName.toUpperCase();
              },
              preventFullImport: true
            }
          }]
        ]
      }
    }
  }]
}

Version 2.0 Breaking Changes

Version 2.0 of this plugin targets Babel 7. Since Babel 7 allows for JS inside the config via .babelrc.js or babel.config.js, the specialized transforms camelCase, kebabCase, and snakeCase have been dropped. If you still need this functionality, you can import lodash directly in your config file and use those functions as part of a return value passed to the transform function (see Using a function as the transformer above).

If you are on Babel 6, this plugin should still work, but if you need the prior specialized functionality, please use the ^1.0.0 version of this library and see the documentation located here.

Options

Name	Type	Required	Default	Description
transform	string or function	yes	undefined	The library name to use instead of the one specified in the import statement. ${member} will be replaced with the import name, aka Grid/Row/Col/etc., and ${1-n} will be replaced by any matched regular expression groups. If using a JS Babel config file, a function may be passed directly. (see Advanced Transformations)
preventFullImport	boolean	no	false	Whether or not to throw when an import is encountered which would cause the entire module to be imported.
skipDefaultConversion	boolean	no	false	When set to true, will preserve import { X } syntax instead of converting to import X.