rollup-plugin-typescript-privatify

Custom transformer preset for @rollup/plugin-typescript.

It rewrites TypeScript private class members into runtime-private implementations in 2 modes.

Note: this package is not a direct Rollup plugin. It is a preset for @rollup/plugin-typescript's transformers option. Note: pnpm add typescript is required.

Install

pnpm add -D rollup-plugin-typescript-privatify @rollup/plugin-typescript typescript

Usage

import typescript from '@rollup/plugin-typescript';
import typescriptPrivatify from 'rollup-plugin-typescript-privatify';

export default {
  plugins: [
    typescript({
      transformers: typescriptPrivatify({
        mode: 'hash', // or "weakmap"
      }),
    }),
  ],
};

This package is not a direct Rollup plugin. If you put it in plugins: [], it will throw a usage error and tell you to move it into typescript({ transformers: ... }).

Options

• mode: "hash" | "weakmap" (default: "hash")
  • hash: convert private foo to #foo.
  • weakmap: generate a companion ClassName__private and a WeakMap to store private state/methods.
• hidePrivateDeclarations: boolean (default: false)
  • when true, registers an afterDeclarations transformer to remove private members from declaration AST.
  • if your declarations are produced by another toolchain stage (for example rollup-plugin-dts), this option will not affect that stage.

Use With rollup-plugin-dts

When you bundle declarations with rollup-plugin-dts, use the named plugin export:

import { dts } from 'rollup-plugin-dts';
import { hidePrivateDeclarationsForDts } from 'rollup-plugin-typescript-privatify';

export default {
  input: 'dist/types/index.d.ts',
  output: [{ file: 'dist/index.d.ts', format: 'es' }],
  plugins: [dts(), hidePrivateDeclarationsForDts()],
};

hidePrivateDeclarationsForDts() can run before or after dts(), but placing it after is usually clearer because it operates on bundled declaration output.

weakmap mode shape

For class A, the transformer emits:

• class A__private { ... }
• const __A_private = new WeakMap();
• __A_private.set(this, new A__private()) in constructor
• private method calls become __A_private.get(this).method.call(this, ...)

Notes

• This package is a transformer preset, not a direct Rollup plugin.
• Anonymous classes in weakmap mode fall back to hash mode.