flow-upgrade

A utility for upgrading your codebase to the latest version of Flow.

Install using yarn add flow-upgrade. We expect prettier to be installed as a peer dependency wherever you are running flow-upgrade.

You can then run:

yarn run flow-upgrade <current flow version> <target flow version>

You may also use npx:

npx flow-upgrade <current flow version> <target flow version>

We also supply the flow-codemod binary:

yarn run flow-codemod <codemod name>

If you just want to run a codemod without specifying Flow versions.

Options

all

By default, Flow will only upgrade files that have an // @flow header comment. If you want to upgrade all of your JavaScript files you may pass in the --all:

yarn create flow-upgrade --all

prettierrc

Path to a .prettierrc file to use. Upgrade codemods rely upon prettier to print the resulting code after transformation. If this is not provided, we will just use the defaults.

Codemods available

Collapse object initialization

Converts static object assignments (e.g. const o = {}; o.a = 1;) to inline properties (e.g. const o = {a: 1};).

Run with yarn run flow-codemod collapseObjectInitialization.

Convert type parameter bound exact empty object to inexact

Replaces T: {} with T: {...} in type parameter bounds. The former is almost always wrong.

Run with yarn run flow-codemod typeParameterBoundExactEmptyObjectToInexact.

Convert implicit inexact object types

Converts implicitly inexact object type syntax {} to explicitly inexact {...}.

Run with yarn run flow-codemod convertImplicitInexactObjectTypes.

Remove explicitly exact object type syntax

Converts explicitly exact object type syntax {| |} to be just be { }. To be done after you turn on exact_by_default=true in your .flowconfig.

Run with yarn run flow-codemod removeExplicitlyExactObjectTypeSyntax.

Remove annotations in destructuring

Removes annotations nested inside of destructuring (e.g. const [o: number] = foo;). These are not valid Flow syntax.

Run with yarn run flow-codemod removeAnnotationsInDestructuring.

Part of the upgrade to 0.176

Remove duplicate class properties

Removes useless duplicate class properties and fixes bad constructor binding in those classes.

Run with yarn run flow-codemod removeDuplicateClassProperties.

Part of the upgrade to 0.170

Rename $Partial to Partial

Renames usages of the $Partial utility type to its new name, Partial.

Run with yarn run flow-codemod renamePartial.

Part of the upgrade to 0.201

Convert $Shape to Partial

Converts usages of the deprecated and unsafe $Shape utility type to its replacement, Partial.

Run with yarn run flow-codemod convertShapeToPartial.

Migrate type casts (x: T) to as expressions x as T

Converts usages of the old casting syntax (x: T) to the new casting syntax x as T.

Run with yarn run flow-codemod typeCastToAsExpression.