Registry / web-framework / fast-flow-transform

fast-flow-transform

library0.0.3jsnpmunverified

A native Hermes/FFT-based Flow type stripper built on napi-rs, providing programmatic transform, CLI, and bundler adapters for webpack, rspack, rsbuild, Parcel, Vite, Rollup, Rolldown, and esbuild. Current version 0.0.3 (pre-1.0, rapid iteration). Differentiator: uses the battle-tested Hermes parser (same as Metro/React Native) for speed and correctness, supports source map merging, removes empty type-only value imports automatically, and offers a 'preserve' format mode (experimental) that keeps whitespace structure. Compared to alternatives like babel-plugin-flow, it is purpose-built for stripping Flow types without transforming JSX or other syntax.

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npm install fast-flow-transform

github ↗package ↗

INSTALL

IMPORT

SIG · FAST-FLOW-TRANSFOR

fast-flow-transform

web-frameworkjavascriptv0.0.3

Install

—

Import

—

Disk

—

Pass rate

0/ 6

Env Coverage0 / 6

glibc

18–22

musl

18–22

Install & Compatibility

Where this runs

tested against v? · npm install

Install × environment matrix

Each cell = how many times install + import succeeded across repeated harness runs. Partial = flaky.
glibc = Debian/Ubuntu slim · musl = Alpine Linux

musl

node 18–223 runs

build_error

glibc

node 18–223 runs

build_error

Code

Verified usage

Verified import paths — ran on the pinned version, not inferred.

transform

✓ import transform from 'fast-flow-transform';

✗ import { transform } from 'fast-flow-transform';

Default export only. Named export does not exist.

transform (CJS)

✓ const transform = require('fast-flow-transform');

✗ const { transform } = require('fast-flow-transform');

CommonJS require returns the default export directly, not an object with a transform property.

TypeScript types

✓ import type { TransformOptions } from 'fast-flow-transform';

✗ import { TransformOptions } from 'fast-flow-transform';

Types are exported as value-like symbols; use `import type` for type-only imports to avoid runtime side-effects.

Shows basic programmatic usage: importing the default transform function, passing a Flow source string with filename and sourcemap enabled, and logging the stripped output.

import transform from 'fast-flow-transform'; const { code, map } = await transform({ filename: '/path/to/input.js', source: ` // @flow function greet(name: string): string { return 'Hello, ' + name; } `, sourcemap: true, comments: true, }); console.log(code); // Output (stripped): function greet(name) { return 'Hello, ' + name; } console.log(map); // Source map object

fast-flow-transform --version

Debug

Known issues

breakingSource map merge does not preserve upstream sourcesContent or custom metadata fields.

fix

If you need full source map chain fidelity, work with babel-plugin-flow or wait for a future release.

affects: >=0.0.1

gotchaFlow enums lower to flow-enums-runtime package. Generated code imports it at runtime.

fix

Install flow-enums-runtime as a production dependency if your project uses Flow enums.

affects: >=0.0.1

gotchaEmpty type-only value imports are removed. This may break code expecting side-effect imports that are actually type-only.

fix

If you need to retain an import that appears type-only but has runtime side effects, mark it with a comment or restructure imports.

affects: >=0.0.3

deprecatedreactRuntimeTarget option only affects Flow component lowering. It does not change JSX handling.

fix

Use reactRuntimeTarget only when using Flow component syntax with React 18 vs 19. For pure type stripping, omit it.

affects: >=0.0.1

gotchaPreserve format mode is experimental. Output may differ from input whitespace.

fix

Stick to 'compact' or 'pretty' for production. Test preserve mode thoroughly.

affects: >=0.0.1

Errors

Common errors & fixes

Error: Cannot find module 'flow-enums-runtime'

Generated code imports flow-enums-runtime when Flow enums are lowered, but it is not installed.

fix

npm install flow-enums-runtime or add to dependencies.

TypeError: (0 , fast_flow_transform_1.default) is not a function

Named import { transform } used instead of default import.

fix

Use import transform from 'fast-flow-transform' or const transform = require('fast-flow-transform').

SyntaxError: Unexpected token (1:16) - Flow syntax not stripped

transform was called without waiting for promise (missing await) or source was not passed correctly.

fix

Ensure transform is awaited: const result = await transform({...}).

Error: Could not resolve 'fast-flow-transform'

Package not installed or mismatched version in package.json.

fix

npm install fast-flow-transform@latest

Upgrade

Version history

0.0.3latest on npm

Audit

Dependencies

@parcel/pluginoptionalPeer dependency for Parcel adapter

@parcel/source-mapoptionalPeer dependency for Parcel adapter source map handling

viteoptionalPeer dependency for Vite plugin (v7.0.0 or later)

Agent activity

8 hits · last 30 days

node

Resources

githubhttps://github.com/jbroma/fast-flow-transform ↗

packagehttps://www.npmjs.com/package/fast-flow-transform ↗