BunPlugin.setup method | Bun module | Bun

A function that will be called when the plugin is loaded.

This function may be called in the same tick that it is registered, or it may be called later. It could potentially be called multiple times for different targets.

A builder object that can be used to register plugin hooks

The builder object passed to Bun.plugin

The config object passed to Bun.build as is. Can be mutated.

Create a lazy-loaded virtual module that can be imported or required from other modules

The module specifier to register the callback for

The function to run when the module is imported or required

this for method chaining

Bun.plugin({
setup(builder) {
builder.module("hello:world", () => {
return { exports: { foo: "bar" }, loader: "object" };
});
},
});

// sometime later
const { foo } = await import("hello:world");
console.log(foo); // "bar"

// or
const { foo } = require("hello:world");
console.log(foo); // "bar"

Register a callback which will be invoked when bundling ends. This is called after all modules have been bundled and the build is complete.

this for method chaining

const plugin: Bun.BunPlugin = {
name: "my-plugin",
setup(builder) {
builder.onEnd((result) => {
console.log("bundle just finished!!", result);
});
},
};

Register a callback to load imports with a specific import specifier

The constraints to apply the plugin to

The callback to handle the import

this for method chaining

Bun.plugin({
setup(builder) {
builder.onLoad({ filter: /^hello:world$/ }, (args) => {
return { exports: { foo: "bar" }, loader: "object" };
});
},
});

Register a callback to resolve imports matching a filter and/or namespace

The constraints to apply the plugin to

The callback to handle the import

this for method chaining

Bun.plugin({
setup(builder) {
builder.onResolve({ filter: /^wat$/ }, (args) => {
return { path: "/tmp/woah.js" };
});
},
});

Register a callback which will be invoked when bundling starts. When using hot module reloading, this is called at the start of each incremental rebuild.

this for method chaining

Bun.plugin({
setup(builder) {
builder.onStart(() => {
console.log("bundle just started!!")
});
},
});