Hola, I am trying to replace eslint-plugin-flowtype with eslint-plugin-ft-flow and there is a new rule ft-flow/enforce-suppression-code. Unfortunately, it fails in many files on our codebase with the following error:

$ /Users/martinzlamal/Work/adeira/universe/node_modules/.bin/eslint src/sx-design/src/constants.js

Oops! Something went wrong! :(

ESLint: 7.32.0

TypeError: Cannot read properties of undefined (reading 'startsWith')
Occurred while linting /Users/martinzlamal/Work/adeira/universe/src/sx-design/src/constants.js:19
    at /Users/martinzlamal/Work/adeira/universe/node_modules/eslint-plugin-ft-flow/dist/rules/enforceSuppressionCode.js:21:17
    at Array.forEach (<anonymous>)
    at isMissingSuppressionCode (/Users/martinzlamal/Work/adeira/universe/node_modules/eslint-plugin-ft-flow/dist/rules/enforceSuppressionCode.js:20:33)
    at handleComment (/Users/martinzlamal/Work/adeira/universe/node_modules/eslint-plugin-ft-flow/dist/rules/enforceSuppressionCode.js:32:24)
    at Array.forEach (<anonymous>)
    at Program (/Users/martinzlamal/Work/adeira/universe/node_modules/eslint-plugin-ft-flow/dist/rules/enforceSuppressionCode.js:41:119)
    at /Users/martinzlamal/Work/adeira/universe/node_modules/eslint/lib/linter/safe-emitter.js:45:58
    at Array.forEach (<anonymous>)
    at Object.emit (/Users/martinzlamal/Work/adeira/universe/node_modules/eslint/lib/linter/safe-emitter.js:45:38)
    at NodeEventGenerator.applySelector (/Users/martinzlamal/Work/adeira/universe/node_modules/eslint/lib/linter/node-event-generator.js:293:26)

The simplest file where this is happening is probably: https://github.com/adeira/universe/blob/02aa03c955c17ebb4a60d4f1f7ce65c19943f9ac/src/sx-design/src/constants.js (clone the repo and run yarn eslint src/sx-design/src/constants.js to reproduce)

Thanks for having a look! 😊

The eslint rules are for flowtype, we might as well flowtype the project to give more stability, consistency

I'd like to ensure no side effects are introduced by type imports, that means if I only import a type from a module, it should use the declaration syntax (import type { X } from 'y').

If I import a mix of types and normal exports from a module though, I don't care about this:

// this separation is not useful as the first import will run any module side effects.
import { X } from 'y';
import type { Z } from 'y';

Right now the type-import-style rule doesn't allow to specify this. Do you think it could be implemented?

I have noticed two issues around type parameters:

1. Function type parameters get spaces
2. Utility functions such as $NonMaybeType and indexed accessor

My .eslintrc

Issue 1

When using a React state hook I want to explicitly type the state property useState<?string>(null). This is being formatted as useState < ?string > (null); by the plugin. This causes no linting warnings or errors based on recommended settings.

Issue 2

When using $NonMaybeType with indexed types I get a trailing space added $NonMaybeType<SomeType['someNestedArray'][0]> comes out like $NonMaybeType<SomeType['someNestedArray'][0] >. This now throws a linting warning (recommended settings) that the generic parameter should not have trailing spaces.

I would love to contribute, if I have time to take a look. Let me know if this is expected behaviour.

globalScope.__defineGeneric is not a funtion

Hello. What problem do I try to solve: we try to migrate our out-of-date flow to the latest version, and on the way installed ft-flow to lint it. We have no-undef rule, and need to override it for flow internal types, i.e. $Values<...>, $Keys<...>, ..., because they conflict with eslint's no-undef now.
I'm trying to add ft-flow to .eslintrs.js, which kinda works until I start adding rules beyond recommended extension. My config (relevant parts, I guess):

module.exports = {
  parser: 'hermes-eslint',
  parserOptions: {
    ecmaVersion: 9,
    sourceType: 'module',
    ecmaFeatures: {
      jsx: true,
    },
    babelOptions: {
      configFile: path.resolve(__dirname, './babel.config.js'),
    },
  },
  extends: [
    // ...
    'plugin:ft-flow/recommended'
  ],
  plugins: [
    'ft-flow',
    // ...
  ],
  env: {
    browser: true,
    jquery: true,
    node: true,
    jest: true,
    es6: true,
  },
  root: true,
  rules: {
    'ft-flow/use-flow-type': 1,
    'ft-flow/define-flow-type': 1, // this rule breaks
    // ...
  },
  // ...
}

The line of code where I get the error (I guess, $Values<...> breaks it)

export type ResourceType = $Values<typeof RESOURCE_TYPES>

ESLint: 8.56.0

TypeError: globalScope.__defineGeneric is not a function
Occurred while linting [some js file here]
Rule: "ft-flow/define-flow-type"
    at makeDefined (PATH/node_modules/eslint-plugin-ft-flow/dist/rules/defineFlowType.js:28:21)
    at GenericTypeAnnotation (PATH/node_modules/eslint-plugin-ft-flow/dist/rules/defineFlowType.js:67:9)
    at PATH/node_modules/eslint/lib/linter/timing.js:141:28
    at ruleErrorHandler (PATH/node_modules/eslint/lib/linter/linter.js:1076:28)
    at PATH/node_modules/eslint/lib/linter/safe-emitter.js:45:58
    at Array.forEach (<anonymous>)
    at Object.emit (PATH/node_modules/eslint/lib/linter/safe-emitter.js:45:38)
    at NodeEventGenerator.applySelector (PATH/node_modules/eslint/lib/linter/node-event-generator.js:297:26)
    at NodeEventGenerator.applySelectors (PATH/node_modules/eslint/lib/linter/node-event-generator.js:326:22)
    at NodeEventGenerator.enterNode (PATH/node_modules/eslint/lib/linter/node-event-generator.js:340:14)

There is similar issue in your legacy (right?) project, but no solutions provided whatsoever. What can I do? Or maybe this is a bug? Thank you in advance.

type TypographyPathifyT = {
  [key in keyof TypographyVariantsT]: string,
};

Will first produce 'key' is defined but never used.eslint[no-unused-vars](https://eslint.org/docs/latest/rules/no-unused-vars) and then using mapped types more will produce, 'key' is already defined.eslint[no-redeclare](https://eslint.org/docs/latest/rules/no-redeclare)

I feel like this name would be more descriptive. The rule doesn't catch only $FlowFixMe but other suppression comments as well, see:

Related discussion here: #14

I opened this issue: facebook/hermes#1311

But not totally sure where the best place for asking this is, so repeating:

In ft-flow, there is this line:

node_modules/eslint-plugin-ft-flow/dist/rules/defineFlowType.js:75:44

      var newGetScope = context.sourceCode.getScope;

Which errors with:

TypeError: Cannot read properties of undefined (reading 'getScope')

Based on the error, it says while trying to lint this line:

import typeof Yargs from 'yargs';

If I switch to @babel/eslint-parser and version 2.0.3 then it passes just fine.
I updated from 2.0.3 to 3.0.4 due to: facebook/hermes#1285

Details here,
gajus/eslint-plugin-flowtype#500

I think this rule is a really good idea. I have a suggestion for improvements though before I can enable it in our codebase. For example, this should be an error (I actually thought this is what the rule is supposed to catch):

// @flow strict

export const test: $FlowFixMe = 42;

Flow is happy, Eslint rule is happy (it should not be). Another example which I think is wrong is this:

// @flow strict

// $FlowExpectedError[incompatible-type]
export const test: string = 42;

It's wrong because it's a Flow test (__flowtests__/test.js) and the error is expected to happen ($FlowExpectedError). In other words, it's correct that Flow complains here (I marked it as expected) but it doesn't mean the file cannot be strict. This case is actually very common in our codebase where we have many strictly typed flow test files. It would be correct if the suppression was for example $FlowFixMe or $FlowIssue.

What do you think about this?

https://github.com/flow-typed/eslint-plugin-ft-flow/blob/master/src/utilities/getBuiltinRule.js
This file looks very outdated, maybe need to investigate and cleanup

I couldn't figure it out yet, but once I add extends: ['plugin:ft-flow/recommended'] the linter crashes for enum types:

yarn run v1.22.17
$ ./node_modules/.bin/eslint ./app.js

app.js
  22:7  error  Parsing error: Unexpected token, expected "{" (22:7)

✖ 1 problem (1 error, 0 warnings)

Without ft-flow/recommended it works though.

The current main README.md is templated and can only be created on master, it uses a tool called gitdown. Ideally this shouldn't be hard to simply it into a node script so it can be run anywhere

Currently yarn test just runs every test, and if you want to filter it down you have to comment out test suites which is a really clunky process. Maybe some cli options with mocha or swap out to jest or something

We just released v0.8.0 of hermes-eslint.
As of this release we have full support for ESLint 8+ - meaning we support the latest ESTree syntax for class properties, class private properties and optional chaining.

hermes-eslint also has a fully-featured scope analyser which understands flow types. This means that the rules ft-flow/define-flow-type and ft-flow/use-flow-type are no longer needed! Also fun side-note that the rules react/jsx-uses-react and react/jsx-uses-vars are not needed because the analyser also supports JSX!

Worth noting that this will also reveal a bunch of no-undef errors in codebases because types are now analysed by the lint rule and types like $ReadOnly are global and have no global declared by ESLint. So no-undef should ideally be turned off in the recommended config. Flow checks this anyway, so it's a superfluous rule.