8000 Why do I get "Avoid referencing unbound methods which may cause unintentional scoping of `this`. eslint@typescript-eslint/unbound-method" in this case? · Issue #102 · sveltejs/eslint-plugin-svelte3 · GitHub
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Why do I get "Avoid referencing unbound methods which may cause unintentional scoping of this. eslint@typescript-eslint/unbound-method" in this case? #102

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frederikhors opened this issue Mar 17, 2021 · 17 comments · Fixed by sveltejs/svelte#6094
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Why do I get "Avoid referencing unbound methods which may cause unintentional scoping of this. eslint@typescript-eslint/unbound-method" in this case? #102

frederikhors opened this issue Mar 17, 2021 · 17 comments · Fixed by sveltejs/svelte#6094

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@frederikhors
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I'm using Svelte 3, Typescript and this code:

  • loginStore.ts:
import { writable } from "svelte/store";

const store = () => {
  const state = {
    isLoggedIn: false,
  };

  const { subscribe, update } = writable(state); // warning: Avoid referencing unbound methods which may cause unintentional scoping of `this`. eslint@typescript-eslint/unbound-method (2 times)

  const methods = {
    OnInit() {
      this.Login(); // warning: Unsafe member access .Login on an any value. eslint@typescript-eslint/no-unsafe-member-access and another warning: Unsafe call of an any typed value. eslint@typescript-eslint/no-unsafe-call
    },

    Login() {
      if (window.localStorage.isLoggedIn) {
        update(() => {
          state.isLoggedIn = true;
          return state;
        });
      }
    },

    async Logout() {
      await doLogout();
      update(() => {
        state.isLoggedIn = false;
        return state;
      });
    },
  };

  return {
    subscribe,
    ...methods,
  };
};

export default store();

But @typescript-eslint is giving me these errors:

  1. Avoid referencing unbound methods which may cause unintentional scoping of this 2 times on line:

    const { subscribe, update } = writable(state)

  2. Unsafe member access .Login on an any value on line:

    this.Login()

  3. Unsafe call of an any typed value on line:

    this.Login()

How can I fix these warnings?
@JounQin
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JounQin commented Mar 17, 2021 •
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There is nothing related to this plugin...

And it's expected AFAIK.

For the first one, writable/subscribe/update is a plain function without this used inside, so if you want, we should change the source svelte code from export function writable() to export const writable = () or export function writable (this: never).

For the other warnings, can just add

OnInit(this: typeof methods)

@frederikhors
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we should change the source svelte code from export function writable() to export const writable = () or export function writable (this: never)

Do you mean we should change Svelte 3 types?

@frederikhors
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frederikhors commented Mar 17, 2021 •
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OnInit(this: typeof methods)

It doesn't fix the warning.

Can you please elaborate on this?

@JounQin
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JounQin commented Mar 18, 2021 •
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OnInit(this: typeof methods)

It doesn't fix the warning.

Can you please elaborate on this?

Sorry about that, actually I don't have the problem.

playground

@JounQin
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JounQin commented Mar 18, 2021

we should change the source svelte code from export function writable() to export const writable = () or export function writable (this: never)

Do you mean we should change Svelte 3 types?

Yes.

@frederikhors
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OnInit(this: typeof methods)

It doesn't fix the warning.
Can you please elaborate on this?

Sorry about that, actually I don't have the problem.

playground

I cannot see your code there:

image

@JounQin
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JounQin commented Mar 18, 2021

What's code do you want, the playground is simplified to show what the root cause.

And which version of typescript and @typescript-eslint/eslint-pluin are you using.

@JounQin JounQin mentioned this issue Mar 18, 2021
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@frederikhors
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I changed the PLAYGROUND, as you can see here this is any.

image

@frederikhors
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frederikhors commented Mar 18, 2021 •
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I'm using:

"@typescript-eslint/eslint-plugin": "4.17.0",
"@typescript-eslint/parser": "4.17.0",
"typescript": "4.2.3",

With this tsconfig.json:

{
  "extends": "@tsconfig/svelte/tsconfig.json",

  "compilerOptions": {
    "module": "ES2020",
    "target": "ES2020",
    "types": ["svelte", "node"]
  },

  "include": ["src/**/*", "types"],
  "exclude": ["node_modules/*", "__sapper__/*", "public/*"]
}

And .eslintrc.js:

module.exports = {
  root: true,
  overrides: [
    {
      files: ['./*.js', './.*.js'],
      env: { node: true },
      parserOptions: { sourceType: 'module', ecmaVersion: 2020 },
      extends: ['eslint:recommended']
    },

    {
      files: ['*.svelte'],
      processor: 'svelte3/svelte3',
      env: { es6: true, browser: true },
      parser: '@typescript-eslint/parser',
      parserOptions: {
        tsconfigRootDir: __dirname,
        project: './tsconfig.json',
        extraFileExtensions: ['.svelte']
      },
      extends: [
        'eslint:recommended',
        'plugin:@typescript-eslint/recommended',
        'plugin:@typescript-eslint/recommended-requiring-type-checking'
      ],
      plugins: ['svelte3', '@typescript-eslint'],
      settings: { 'svelte3/typescript': require('typescript') },
      rules: {
        '@typescript-eslint/no-unsafe-member-access': 0
      }
    },

    {
      files: ['*.ts', '*.tsx'],
      env: { es6: true, browser: true },
      parser: '@typescript-eslint/parser',
      parserOptions: {
        tsconfigRootDir: __dirname,
        project: './tsconfig.json',
        extraFileExtensions: ['.svelte']
      },
      extends: [
        'eslint:recommended',
        'plugin:@typescript-eslint/recommended',
        'plugin:@typescript-eslint/recommended-requiring-type-checking'
      ],
      plugins: ['svelte3', '@typescript-eslint'],
      settings: { 'svelte3/typescript': require('typescript') }
    }
  ]
}

@JounQin
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JounQin commented Mar 18, 2021 •
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Maybe it's time to provide a runnable reproduction now.

I don't know what's wrong with your playground.

image

@frederikhors
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It works now on my Playground. But I still have that problem locally. What's the typescript version of the playground?

@JounQin
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JounQin commented Mar 18, 2021

https://github.com/armano2/typescript-eslint/blob/docs-page/package.json#L126

@frederikhors
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Ok. I have the reproducible repo: https://github.com/frederikhors/issueWithThisAny

image

@JounQin
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JounQin commented Mar 18, 2021 •
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@frederikhors

If you enabled "noImplicitThis": true compileOption, it will just work.

Anyway, it's a ts usage problem, not related to eslint-plugin-svelte3 at all.

raised typescript-eslint/typescript-eslint#3197 for better message.

@JounQin JounQin mentioned this issue Mar 18, 2021
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@frederikhors
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Should we add "noImplicitThis": true to https://github.com/sveltejs/template/blob/master/scripts/setupTypeScript.js? What do you think?

@dummdidumm
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No, that's up to the user to decide how strict he wants his type checking.

@frederikhors
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I can close this. You people are wonderful people!

@JounQin JounQin mentioned this issue Mar 18, 2021
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dummdidumm pushed a commit to sveltejs/svelte that referenced this issue Mar 24, 2021
@JounQin
chore: add this: void typing to store functions (#6094)
50dcc2a 
This is necessary so ESLint does not complain about possibly unbound method access
fixes sveltejs/eslint-plugin-svelte3#102
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chore: mark nest method this: void for destructing safely
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@dummdidumm @JounQin @frederikhors
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