rollup-plugin-your-function

A very simple rollup-plugin, which gives you the opportunity to manipulate your build files as you like. Dead simple. The last plugin you need (for small tasks).

Idea

There are many plugins for rollup available. And many times the only thing you would like to perform is a little change, just some regex magic, only a small string replacement, etc. Now the big research begins: which plugin fits the best?

Eventually you will find what you need, but now you'll have to figure out the particularities of the plugin. And you find yourself thinking: "Why was that so complicated? I could have done this to a regular file in seconds!".

This is where rollup-plugin-your-function comes into play. The only! thing it does, is to take a function, that you create by yourself. Your function needs to take one argument, that is the source file, it must return the output code as the first parameter, optionally a sourcemap as a second (otherwise it gets generated automatically and includes the performed changes). And that's it.

Install

Using npm:

npm install rollup-plugin-your-function --save-dev

Usage

Create a rollup.config.js configuration file and import the plugin.

import { yourFunction } from "rollup-plugin-your-function";

export default {
    input: "src/index.js",
    output: {   
        format: "es",
        name: "myBuild",
        file: "./dist/build.js",
    },
    plugins: [
        yourFunction({
            fn: source => {
                let code = source.replace("foo", "bar");
                code += "baz";
                return code;
            }
        })
    ]
}

...or use it as an output plugin

import { yourFunction } from "rollup-plugin-your-function";

const myPlugin = yourFunction({
    output: true,
    name: "myPlugin",
    fn: async (source, options) => ...
});

export default {
    input: "src/index.js",
    output: {   
        format: "es",
        name: "myBuild",
        file: "./dist/build.js",
        plugins: [myPlugin()]
    }
}

Then call rollup either via the CLI or the API.

Options

include

Type: String | Array[...String]
Default: null

A minimatch pattern, or array of patterns, which specifies the files in the build the plugin should operate on. By default all files are targeted.

exclude

Type: String | Array[...String]
Default: null

A minimatch pattern, or array of patterns, which specifies the files in the build the plugin should ignore. By default no files are ignored.

fn

Type: Function
Default: null

This is your function. Create a function (sync or async) that takes one argument (the source input), optionally a second parameter can be provided to have access to the options.

The manipulated code can be returned as a:

• string
• an array with the code at index 0 and an optional sourcemap at index 1
• code and the optional map inside of an object ({code: <code>, map: <map>}).

// Example A:
fn: source => {
    let code = source.replace("foo", "bar");
    return code;
}

// Example B:
fn: (source, options) => {
    let code = source.replace("foo", "bar");
    let map = mySourcemapGeneratingFN();

    if (options.id === "my-file") {
        console.log("my-file is currently getting processed");
    }
    
    return [ code, map ];
}

// Example C:
fn: source => {
    let code = source.replace("foo", "bar");
    let map = mySourcemapGeneratingFN();
    return { code, map };
}    

options

For global plugins, only the id is available (which is the filename). Output plugins also have access to the following parameters:

• chunk
• outputOptions
• meta

More information on those parameters can be found at the rollup documentation.

output

Type: Boolean
Default: false

Set to true if you want your function to be passed to the output file.

showDiff

Type: String
Default: null

A debugging method. If set to anything other than the string "file" a console output of diff is shown. It is modified a little and looks much like the default output of diff from the GNU diffutils, with colors on top. If set to "file" the whole file with insertions and deletions is shown. Either way it only gets logged if there are any changes at all.

License

MIT

Copyright (c) 2022, UmamiAppearance