@hasnat/babel-plugin-transform-imports

Transforms member style imports (import {x} from 'y') into default style imports (import x from 'y/lib/x')


Keywords
babel, transform, import, react-bootstrap, lodash
License
ISC
Install
npm install @hasnat/babel-plugin-transform-imports@1.4.1

Documentation

babel-plugin-transform-imports

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

In .babelrc:

{
    "plugins": [
        ["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": [
        ["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 .babelrc.js file, you may provide a function instead of a string for the transform option:

.babelrc.js:

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

Using a transformation file

If you need the above flexibility of using a function as a transformer, but are still on Babel 6 or cannot use a .babelrc.js file for some reason, you may provide a path to a .js file which exports a function to run instead. Keep in mind that the .js file will be required relative from this plugin's path, likely located in /node_modules/babel-plugin-transform-imports. You may provide any filename, as long as it ends with .js.

.babelrc:

{
    "plugins": [
        ["transform-imports", {
            "my-library": {
                "transform": "../../path/to/transform.js",
                "preventFullImport": true
            }
        }]
    ]
}

/path/to/transform.js:

module.exports = function(importName, matches) {
    return 'my-library/etc/' + importName.toUpperCase();
};

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
                        }
                    }]
                ]
            }
        }
    }]
}

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. Alternatively, pass a path to a .js file which exports a function to process the transform, which is invoked with parameters: (importName, matches). If using Babel 7+, 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.
camelCase boolean no false When set to true, runs ${member} through _.camelCase.
kebabCase boolean no false When set to true, runs ${member} through _.kebabCase.
snakeCase boolean no false When set to true, runs ${member} through _.snakeCase.
skipDefaultConversion boolean no false When set to true, will preserve import { X } syntax instead of converting to import X.