node package manager


flow-annotation-check Build Status

Verify the @flow and @flow weak annotations in your javascript files.

Install with NPM:

npm install flow-annotation-check

or use the global flag to easily run from bash:

npm install --global flow-annotation-check

As a library

Once installed you can import flow-annotation-check into your own module and have the checker return a list of files for you to further process.

const flowAnnotationCheck = require('flow-annotation-check');

The most useful methods are:

  • genReport(folder: string, config: Config): Promise<Array<FileReport>>
  • getStatus(filePath: string): Promise<FlowStatus>

The types involved are:

type Glob = string; // See 
type Config = {
  include: Array<Glob>,
  exclude: Array<Glob>,
  absolute: boolean,
type FlowStatus = 'flow' | 'flow weak' | 'no flow';
type FileReport = {
  file: string,
  status: FlowStatus,

genReport(folder, config)

If you want to check a whole project at once, then call genReport. You can pass in the root folder, like ~/my-project/src and then a configuration object with some glob strings to find your files. genReport will return a Promise that will resolve when all matching files have had their flow-status discovered.

This is a convienence method to make working with globs and mapping over getStatus easier. Each file is tested serially in order to avoid setting really long timeouts that lock up the flow server.

    include: ['**/*.js'],
    exclude: ['**/*.coffee'],
    absolute: true,
).then((entries) => {
  entries.forEach((entry) => {
    console.log(entry.status + "\t" + entry.file);


If you're checking one file at a time then go ahead and call getStatus directly. This takes a string that will be passed directly into flow on the command line.

const file = '~/path/to/project/src/main.js';
flowAnnotationCheck.getStatus(file).then((status) => {
  console.log(`The status of ${file} is ${status}`);


If you don't want to install the package globally you can run flow-annotation-check from the CLI by adding it to your package.json file:

  "scripts": {
    "annotations": "flow-annotation-check"

Then run that script:

npm run annotations

or if installed globally:

flow-annotation-check ~/path/to/project

The available commands can be found by running flow-annotation-check -h or npm run annotations -- --help.

The common settings you will use are:

  • -i, --include Glob for files to include. Can be set multiple times.
  • -x, --exclude Glob for files to exclude. Can be set multiple times.
  • -a, --absolute Report absolute path names. The default is to report only filenames.

Validate mode

Flow has some internal limits on what annotations it will detect. This might mean some files might not report errors when you run flow check on the cli (see in facebook/flow). You can use the validate command to verify your existing annotations.

‼️⚠️ Save your work because --validate will modify files in your local filesystem. ⚠️‼️

flow-annotation-check --validate