flow-remove-types: the "checkPragma" option has been…

Error message

flow-remove-types: the "checkPragma" option has been replaced by "all".

What it means

Thrown by flow-remove-types' main transform function when the options object contains a `checkPragma` key. In v1.x, `checkPragma: false` told the tool to strip types from every file; v2.x removed that option and replaced it with the inverted `all` option (`all: true` transforms every file, otherwise only files with an @flow/@noflow pragma are processed). The check fires before any parsing, so nothing runs until the config is fixed.

Solutions

Remove `checkPragma` from the options object entirely.
If you relied on `checkPragma: false` (transform files without a pragma), switch to `all: true`.
If you relied on `checkPragma: true` (default pragma detection), pass no option - that is the v2 default.
Grep the repo for `checkPragma` to catch every transform/register entry point.

Example fix

// before
require('flow-remove-types/register')({checkPragma: false});

// after
require('flow-remove-types/register')({all: true});

Defensive patterns

Strategy: validation

Validate before calling

function sanitizeFlowRemoveTypesOptions(options) {
  if (!options || !('checkPragma' in options)) return options;
  const {checkPragma, ...rest} = options;
  // v1 checkPragma:false meant transform everything -> v2 all:true
  if (checkPragma === false) rest.all = true;
  return rest;
}

// use
const out = flowRemoveTypes(source, sanitizeFlowRemoveTypesOptions(opts));

Prevention

Grep for 'checkPragma' after every flow-remove-types major upgrade.
Keep transform options in one shared module so there is a single place to migrate.
Add a smoke test that calls the transform with your production options at startup.

When it happens

Trigger: Calling `require('flow-remove-types')(source, {checkPragma: ...})` (or flow-remove-types/register with the same options) with any value of checkPragma present, e.g. `{checkPragma: false}` left over from a 1.x setup; babel/jest configs that forward the whole options object.

Common situations: Upgrading flow-remove-types (or @babel dependencies that embed it) from 1.x to 2.x without updating build scripts; copied StackOverflow/codemod configs written for the old API; monorepos where one package was upgraded and its config is shared.

Related errors

AI-assisted analysis of facebook/flow@f88ac94bcf (2026-08-20). Data as JSON: /api/errors/1e8e9eef38d0906b. Report an issue: GitHub.

Appendix: source

Thrown at packages/flow-remove-types/index.js:47

 *     COMPLIANT! Instead, use `declare foo: string;` for type-only fields.
 *
 *   - removeEmptyImports: (default: false)
 *     If true, removes empty import statements that remain after removing
 *     all type and typeof imports (e.g. `import {} from 'some-module'`).
 *
 * Returns an object with two methods:
 *
 *   - .toString()
 *     Returns the transformed source code.
 *
 *   - .generateMap()
 *     Returns a v3 source map.
 */
module.exports = function flowRemoveTypes(source, options) {
  // Options
  var all = Boolean(options && options.all);
  if (options && options.checkPragma) {
    throw new Error(
      'flow-remove-types: the "checkPragma" option has been replaced by "all".',
    );
  }

  // If there's no @flow or @noflow flag, then expect no annotation.
  var pragmaStart = source.indexOf('@' + 'flow');
  var pragmaSize = 5;
  if (pragmaStart === -1) {
    pragmaStart = source.indexOf('@' + 'noflow');
    pragmaSize = 7;
    if (pragmaStart === -1 && !all) {
      return resultPrinter(options, source);
    }
  }

  // This parse configuration is intended to be as permissive as possible.
  var ast = parse(source, {flow: all ? 'all' : 'detect', tokens: true});

View on GitHub (pinned to f88ac94bcf)