`globalScope.__defineGeneric` is not a function about eslint-plugin-ft-flow

[e1cb4ac37s]

1. Here it is:

   // @flow
   
   import { Api } from 'services/api' // <- this one

   this looks like it breaks on a first line of the first flow-tagged file, as deleting this line moves an error to the next non-empty one, deleting the file moves error to the next file, first non-empty line.
2. Indeed, commenting them out one-by-one shows that only define-flow-type breaks no-unused-vars, use-flow-type is ok.

[Brianzchen]

^ Merged a fix. Please give a go with v3.0.3 and let me know if it works 🙏

[e1cb4ac37s]

Thank you for a very fast response and fix! ft-flow now does not throw, although eslint's no-unused-vars broke (which was not the case before). But it seems I have to go with this issue to eslint repo now - ft-flow's part works now. Thank you again.

Oops! Something went wrong! :(

ESLint: 8.56.0

TypeError: Cannot read properties of null (reading 'scope')
Occurred while linting PATH/client/src/core/api/some-js-file.js
Rule: "no-unused-vars"
    at getRhsNode (PATH/client/node_modules/eslint/lib/rules/no-unused-vars.js:356:43)
    at PATH/client/node_modules/eslint/lib/rules/no-unused-vars.js:541:27
    at Array.some (<anonymous>)
    at isUsedVariable (PATH/client/node_modules/eslint/lib/rules/no-unused-vars.js:534:40)
    at collectUnusedVariables (PATH/client/node_modules/eslint/lib/rules/no-unused-vars.js:658:26)
    at Program:exit (PATH/client/node_modules/eslint/lib/rules/no-unused-vars.js:677:36)
    at ruleErrorHandler (PATH/client/node_modules/eslint/lib/linter/linter.js:1076:28)
    at PATH/client/node_modules/eslint/lib/linter/safe-emitter.js:45:58
    at Array.forEach (<anonymous>)
    at Object.emit (PATH/client/node_modules/eslint/lib/linter/safe-emitter.js:45:38)

Edit: in fact, I ran eslint without any recommendations (except ft-flow's one with 3 rules:

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,
  globals: {
    globalThis: 'readonly',
  },
  rules: {
    'ft-flow/define-flow-type': 1, // (1)
    'ft-flow/use-flow-type': 1, // (2)
    'no-unused-vars': ['error', { argsIgnorePattern: '^_', ignoreRestSiblings: true }],
  },
  settings: {
    'import/resolver': {
      node: {
        paths: ['.'],
        extensions: ['.js', '.ts', '.jsx', '.tsx'],
      },
      'babel-module': {
        cwd: 'babelrc',
        root: ['./src/'],
        alias: babelAliases,
      },
    },
    'import/external-module-folders': [path.resolve(__dirname, './node_modules/')],
    'import/internal-regex': '^@+foxford',
    react: {
      version: '17',
    },
    flowtype: {
      onlyFilesWithFlowAnnotation: true,
    },
  },
  ignorePatterns: ['.eslintrc.js', '/docs', '/build', '/flow-typed', '**/node_modules/**', '*/*.sass'],
}

commenting out lines (1) and (2) makes `no-unused-vars' work, while keeping them leads to an error above

[Brianzchen]

@e1cb4ac37s can you try 3.0.4-alpha-0. I removed something that seemed unnecessary and was causing issues. It's throwing the unused errors correctly but need to spend more time getting the tests to play nicely together before I can merge and make an official release

[Brianzchen]

Thanks for raising this issue. At first glance it seems to be because __defineGeneric object does not exist in the hermes-eslint parser so I expect it should work with @babel/eslint-parser and as a result it's throwing.

But because with flow you should use hermes-eslint to parse the syntax correctly we'll have to find a solution for you. I'll keep digging to find what the equivalent with hermes would be.

Do note that flow team recommended that this rule isn't necessary anymore hence why we didn't test for this case

[Brianzchen]

Have raised an issue with hermes team. Lets see if they come back with anything useful before I cont my investigation. Otherwise I'll need to understand what that function did in the beginning to find a suitable replacement function

[Brianzchen]

:/ hmm I'll need to reproduce it in tests to find a solution. The change I made was to define-flow-type only and I suspect that when I inject the global variable it's missing something causing the next rule to fail.

    'ft-flow/define-flow-type': 1, // (1)
    'ft-flow/use-flow-type': 1, // (2)

For some more info

1. Could you share the line or token that fails to be parsed causing this error?
2. Is it when both rules are in use or only one?
3. What happens if you only one of define-flow-type or use-flow-type?

[Brianzchen]

Great I was able to reproduce this, turns out we never had a test against no-unused-vars and only tested no-undef and no-use-before-define.

[short-dsb]

FWIW 3.0.4-alpha-0 resolves the issue for me.

[Brianzchen]

Thanks for validating @short-dsb. I'll work on getting my tests working and publish an official release this weekend... Unless someone finds more problems 😨

[e1cb4ac37s]

Works for me now. Awesome job, Brian! Thank you!

[short-dsb]

Thanks, @Brianzchen! Really appreciate it. 🙂