Registry / type-stubs / babel-plugin-reflow

babel-plugin-reflow

library0.5.7jsnpmunverified

Babel plugin to transpile Flow type annotations to TypeScript, with a CLI wrapper for batch conversion. Current stable version 0.5.7 (latest). Development appears slow but active with periodic releases. Key differentiators: focuses on pretty output via Prettier, handles comments well, proven on real projects (27k and 41k LOC). Compared to alternatives like flow-to-ts or babel-plugin-flow-to-typescript, Reflow offers a CLI and better output formatting. Supports base types, generics, utility types, nullable types, optional chaining, nullish coalescing, and class decorator replacement. Limitation: empty Flow object types become `object` not `{}` since v0.5.

type-stubs serialization devops

npm install babel-plugin-reflow

github ↗package ↗

INSTALL

IMPORT

SIG · BABEL-PLUGIN-REFLO

babel-plugin-reflow

type-stubsjavascriptv0.5.7

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 18–226 runs

build_error

glibc

node 18–226 runs

build_error

Code

Verified usage

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

default

✓ import reflow from 'babel-plugin-reflow'

✗ const reflow = require('babel-plugin-reflow')

Plugin is exported as default export. CommonJS require works but TypeScript users should use default import.

ReflowError

✓ import { ReflowError } from 'babel-plugin-reflow'

✗ import ReflowError from 'babel-plugin-reflow'

ReflowError is a named export, not default.

plugin

✓ // .babelrc { "plugins": ["babel-plugin-reflow"] }

✗ { "plugins": ["reflow"] }

Plugin name in Babel config is the full package name.

Demonstrates CLI usage to transpile a directory and programmatic usage with Babel.

// Install: npm install --save-dev babel-plugin-reflow // Run CLI on src directory, replace .js with .ts in-place: // npx reflow --replace src/ // Or with dry run: // npx reflow -d src/ // Programmatic usage: const reflow = require('babel-plugin-reflow'); const babel = require('@babel/core'); const code = ` // @flow function greet(name: string): string { return 'Hello, ' + name; } `; const result = babel.transformSync(code, { plugins: [reflow], filename: 'input.js', }); console.log(result.code); // Output: // function greet(name: string): string { // return 'Hello, ' + name; // }

reflow --version

Debug

Known issues

breakingEmpty Flow object types `{}` are transformed to `object` instead of `{}` since v0.5.0.

fix

Manually replace `object` with `{}` in generated code if `{}` semantics required.

affects: >=0.5.0

deprecatedThe `--exclude-dirs` option is deprecated in favor of `--exclude-patterns`.

fix

Use `--exclude-patterns '**/node_modules/**'` instead.

affects: >=0.4.0

gotchaFlow's `mixed` type is transformed to `unknown` in TypeScript; this may not be type-safe for codebases relying on dynamic access.

fix

Audit uses of `mixed` and add type guards or assertions as needed.

affects: >=0.1.0

gotchaFunction type inference may differ: Flow's exact object types may become less precise.

fix

Review generated types for exact object semantics and add `Readonly` or `as const` as needed.

affects: >=0.1.0

warningPlugin does not handle `$ReadOnlyArray`, `$ReadOnly`, `$Exact` utilities; they may cause errors.

fix

Manually replace with TypeScript equivalents or suppress errors.

affects: >=0.1.0

Errors

Common errors & fixes

Error: Could not find plugin 'babel-plugin-reflow'

Package not installed or not in node_modules.

fix

Run `npm install --save-dev babel-plugin-reflow` or `yarn add --dev babel-plugin-reflow`.

SyntaxError: Unexpected token (1:10) (While processing: ...)

File contains Flow syntax but Babel is not configured to parse Flow first.

fix

Add `@babel/preset-flow` to your Babel presets before the Reflow plugin.

TypeScript error: Type 'object' is not assignable to type '{}'

Reflow v0.5+ converts empty object `{}` to `object` which is not compatible.

fix

Either adjust TypeScript config to allow `object` or manually replace `object` with `{}`.

Error: Unknown option 'exclude-dirs'

Using deprecated CLI option.

fix

Replace `--exclude-dirs` with `--exclude-patterns` and update the pattern syntax.

Upgrade

Version history

0.5.7latest on npm

Audit

Dependencies

@babel/corerequiredBabel plugin runs on Babel core

prettierrequiredUsed for code formatting output

chokidaroptionalUsed in CLI for file watching

Agent activity

34 hits · last 30 days

node

OpenAI (training)

Resources

githubhttps://github.com/grubersjoe/reflow ↗

packagehttps://www.npmjs.com/package/babel-plugin-reflow ↗