Replaces the members of imported namespaces with direct imports.

Before:

import { User } from "#utils";

const email = User.email(user);

After:

import { email as _email } from "#utils/User/email";

const email = _email(user);

This makes namespaces, such as the ones created by @monstermann/barrels, free in bundle size without relying on what a bundler is able to tree-shake.

Installation

bun add -D @monstermann/barrels-treeshake

Usage

You decide which namespaces are replaced and what they are replaced with: resolve is called for each member of an imported namespace and returns the import that should be used instead, or nothing to leave the namespace alone.

import { treeshake } from "@monstermann/barrels-treeshake";

treeshake({
    resolve({ importAlias, importName, importPath, propertyName }) {
        if (importPath !== "#utils") return;
        return `import { ${propertyName} as ${importAlias} } from "#utils/${importName}/${propertyName}";`;
    },
});

| Property | import { Foo as Bar } from "foo"; Bar.baz | Description | | -------------- | ------------------------------------------- | ----------------------------------------------------------- | | importName | "Foo" | "*" for import * as Foo, undefined for import Foo. | | localName | "Bar" | | | importPath | "foo" | | | propertyName | "baz" | | | importAlias | "_baz" | A unique identifier to use as the local name of the import. | | filePath | | The file that is being transformed. | | scope | | All identifiers used in the file. |

resolve can be a list of resolvers, the first result is used.

Vite, Rolldown, tsdown

import { treeshake } from "@monstermann/barrels-treeshake";

export default defineConfig({
    plugins: [treeshake({ enforce: "pre", resolve })],
});

| Option | Default | Description | | --------- | -------------- | ---------------------------------------------------------------------- | | resolve | | See above. | | include | /\.[jt]sx?$/ | RegExp(s), only files whose path matches are transformed. | | exclude | | RegExp(s), files whose path matches are skipped. | | enforce | | "pre" or "post". | | debug | false | true or a RegExp matching file paths, prints what is being replaced. |

Bun

Bun.build only uses the first onLoad that returns something, so call transform from your own:

import { transform } from "@monstermann/barrels-treeshake";

await Bun.build({
    entrypoints: ["./src/index.ts"],
    plugins: [
        {
            name: "transforms",
            setup(build) {
                build.onLoad(
                    { filter: /\.tsx?$/ },
                    async ({ loader, path }) => {
                        const code = await Bun.file(path).text();
                        return {
                            contents:
                                transform(code, path, { resolve })?.code ??
                                code,
                            loader,
                        };
                    },
                );
            },
        },
    ],
});

Standalone

import { transform } from "@monstermann/barrels-treeshake";

const result = transform(code, "source.ts", { resolve });
result?.code;
result?.map;

Details

• Named, default and wildcard imports are supported, as well as JSX (<Foo.Bar />).
• A namespace is left untouched when one of its members is not resolved, or when the namespace itself is needed: const x = Foo, export { Foo }, Foo["bar"], Foo.bar = 1.
• Declarations shadowing an import are respected.
• When a namespace is also used as a type (let rect: Rect = Rect.create()), an import type is kept for it.
• Only the first level is replaced: Foo.bar.baz becomes _bar.baz.