file-replace-loader
file-replace-loader is webpack loader that allows you replace files in compile time by some condition.
file-replace-loader is free and will always remain free
A simple and quick way to support the project is to buy me a coffee.
It will take no more than 5 minutes and will allow the project to keep going
Table of contents
Features
- Compatibility with webpack 3.x, 4.x, 5.x;
- Support watch webpack mode;
- Replace files in compile time without change source files;
- Multiple replacement;
- Sync and async modes;
- Compatibility with other loaders;
- Support binary files.
Installation
NPM
npm install --save-dev file-replace-loader
Yarn
yarn add file-replace-loader
Usage
const { resolve } = require('path');
module.exports = {
module: {
rules: [{
test: /\.config\.js$/,
loader: 'file-replace-loader',
options: {
condition: 'if-replacement-exists',
replacement: resolve('./config.local.js'),
async: true,
}
}]
}
}
This example rule replaces all of imports /\.config.js$/
to config.local.js
file,
if replacement exists (condition if-replacement-exists
).
After this build a bundle file will contain code from config.local.js
and original sources
won't changed.
Multiple replace
To describe replace rules for two or more files you can use function as replacement value.
How does it work?
- Webpack runs file-replace-loader according to
test
rule, include
and exclude
rule options; - file-replace-loader looks on
replacement
option. If it is string then the loader just replace a file. If it is a function
then file-replace-loader checking what it returns. If the function returns a path to file then the loader
replaces, if returns nothing then current match skips. - If
replacement
function returns a path then file-replace-loader looks to condition
. If condition is always
then it replace every match. If condition
is
if-replacement-exists
then loader checking existing file, etc;
For example:
const { resolve } = require('path');
module.exports = {
module: {
rules: [{
test: /\.js$/,
loader: 'file-replace-loader',
options: {
condition: 'always',
replacement(resourcePath) {
if (resourcePath.endsWith('foo.js')) {
return resolve('./bar.js');
}
if (resourcePath.endsWith('foo-a.js')) {
return resolve('./bar-a.js');
}
},
async: true,
}
}]
}
}
file-replace-loader passes to replacement
function resourcePath
for every matching.
file-replace-loader doesn't care what developer does with this path but if repalcement
function returns a new path then file-replace-loader replaces file.
If replacement
function returns nothing then file-replace-loading skip replace for current resourcePath
.
Example with mapping:
const { resolve } = require('path');
module.exports = {
module: {
rules: [{
test: /\.js$/,
loader: 'file-replace-loader',
options: {
condition: 'always',
replacement(resourcePath) {
const mapping = {
[resolve('./src/foo-a.js')]: resolve('./src/bar-a.js'),
[resolve('./src/foo-b.js')]: resolve('./src/bar-b.js'),
[resolve('./src/foo-c.js')]: resolve('./src/bar-c.js'),
};
return mapping[resourcePath];
},
async: true,
}
}]
}
}
NOTE: Make shure that all replacement files contains necessary imports and exports
that other files are expecting.
Using with binary files
file-replace-loader allows replace binary files.
For example:
const { resolve } = require('path');
module.exports = {
module: {
rules: [{
test: /\.png$/,
use: [{
loader: 'file-loader',
options: {
name: '[name].[ext]',
},
}, {
loader: 'file-replace-loader',
options: {
condition: 'if-replacement-exists',
replacement: resolve('./src/replacement.png')
}
}]
}]
}
}
Using with other loaders
file-replace-loader must executes before other loaders. This means that in webpack config file the loader must be last in list.
For example:
const { resolve } = require('path');
module.exports = {
module: {
rules: [{
test: /\.config\.js$/,
use: [{
loader: 'babel-loader',
}, {
loader: 'file-replace-loader',
options: {
condition: 'if-replacement-exists',
replacement: resolve('./config.local.js'),
async: true,
}
}]
}]
},
}
Above is correct example. file-replace-loader will executed before other loaders.
Let's see incorrect usage:
const { resolve } = require('path');
module.exports = {
module: {
rules: [{
test: /\.config\.js$/,
use: [{
loader: 'file-replace-loader',
options: {
condition: 'if-replacement-exists',
replacement: resolve('./config.local.js'),
async: true,
}
}, {
loader: 'babel-loader',
}]
}]
},
}
In incorrect example above file-replace-loader first in rule list.
This case throw an error because file-replace-loader should be last in list.
Loader options
Option | Type | Required | Default | Possible values |
---|
condition Condition to replace | string |boolean | no | 'if-replacement-exists' | true ,
false ,
'always' ,
'never' ,
'if-replacement-exists' ,
'if-source-is-empty' |
replacement Replacement file | string |function (resourcePath, options) | yes | — | Full path to file or function returning full path to file |
async Asynchronous file reading | boolean | no | true | true ,
false |
progress Progress output | boolean | no | IS_DEBUG_MODE == true or IS_PROGRESS_MODE == true | true ,
false |
Contributing
See contributing guideline.
License
MIT LICENSE