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babel-plugin-transform-imports

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.

That's stupid, why would you do that?

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;

Some libraries, such as react-bootstrap and lodash, are rather large and pulling in the entire module just to use a few pieces 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

In cases where the provided default string replacement transformation is not sufficient (for example, needing to execute a RegExp on the import name), you may instead 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) {
    return 'my-library/etc/' + importName.toUpperCase();
};

This is a little bit hacky, but options are a bit limited due to .babelrc being a JSON5 file which does not support functions as a type. In Babel 7.0, it appears .babelrc.js files will be supported, at which point this plugin will be updated to allow transform functions directly in the configuration file. See: https://github.com/babel/babel/pull/4892

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) {
                                    return 'my-library/etc/' + importName.toUpperCase();
                                },
                                preventFullImport: true
                            }
                        }]
                    ]
                }
            }
        }
    ]
}

Options

Name Type Required Default Description
transform string yes undefined The library name to use instead of the one specified in the import statement. ${member} will be replaced with the member, aka Grid/Row/Col/etc. Alternatively, pass a path to a .js file which exports a function to process the transform (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.