Wrong conditional checkings

[mpiorowski]

Before You File a Bug Report Please Confirm You Have Done The Following...

• I have tried restarting my IDE and the issue persists.
• I have updated to the latest version of the packages.

What version of ESLint are you using?

8.23.1

What version of eslint-plugin-svelte are you using?

2.8.0

What did you do?

Simple true/false check.

What did you expect to happen?

No eslitn errors.

What actually happened?

Link to Minimal Reproducible Example

https://github.com/mpiorowski/svelte-eslint-bug/blob/main/src/routes/%2Bpage.svelte

Additional comments

Thank You for fixing my previous issue, Your plugin is much better then the native svelte one :)

[baseballyama]

After remove all pretiier stuff, the issue is gone.
So this is not this ESLint plugin's issue.

But why you need to override parser in .prettierrc?

"overrides": [{ "files": "*.svelte", "options": { "parser": "svelte-eslint-parser" } }]

[mpiorowski]

This overide setting in .prettierrc was the default one when i create new sveltekit project ;p Didn't even notice. Removed it already.

I have removed prettier form eslint and stil have this error @baseballyama .
What excatly did You deleted to make it not throw error?

[baseballyama]

DId you do the below steps?

1. run npm rm eslint-config-prettier eslint-plugin-prettier prettier prettier-plugin-svelte
2. run rm -rf ./node_modules
3. run npm i
4. restart your IDE

[mpiorowski]

@baseballyama did all of it, and the eslint still throw the warning

[ota-meshi]

Probably treated and reported the same as the following typescript-eslint DEMO.

https://typescript-eslint.io/play/#ts=4.8.3&sourceType=module&code=DYUwLgBAlgzg8gBxAOwgXggMwIbBiAbgCgjRIoATALghjACcpkBzCAHwgFdkKRMmQFdFx58BFYsSIAKaQEp0APgjTYiFMICEapMjlyp2+LogAyU9CEB6KxAA8AWgj0QCAPb0wgoA&eslintrc=N4KABGBEBOCuA2BTAzpAXGUEKQAIBcBPABxQGNoBLY-AWhXkoDt8B6Jge1tiacTJTIAhtEK0yHJgBNK+SpPRRE0aB2iRwYAL4gtQA&tsconfig=N4KABGBEDGD2C2AHAlgGwKYCcDyiAuysAdgM6QBcYoEEkJemy0eAcgK6qoDCAFutAGsylBm3TgwAXxCSgA

let isOpen = false;

let id: string | undefined = undefined;
;

(() => (isOpen = !isOpen));

!isOpen && id // <- reported

It might be possible to solve it by creating a temporary scope in the parser and letting typescript build the type information.

let isOpen = false;

let id: string | undefined = undefined;
;
function tmp () {
(() => (isOpen = !isOpen));

!isOpen && id // <- OK
}

https://typescript-eslint.io/play/#ts=4.8.3&sourceType=module&code=DYUwLgBAlgzg8gBxAOwgXggMwIbBiAbgCgjRIoATALghjACcpkBzCAHwgFdkKRMmQFdFx58BFYsUzcAxmCgB7VGAC2CABQBKCAG8iECOq3oAfIdiIUwgIQWkyTZuL6It+PYgAyT9CEB6PwgAHgBaCDgAaSIAXyA&eslintrc=N4KABGBEBOCuA2BTAzpAXGUEKQAIBcBPABxQGNoBLY-AWhXkoDt8B6Jge1tiacTJTIAhtEK0yHJgBNK+SpPRRE0aB2iRwYAL4gtQA&tsconfig=N4KABGBEDGD2C2AHAlgGwKYCcDyiAuysAdgM6QBcYoEEkJemy0eAcgK6qoDCAFutAGsylBm3TgwAXxCSgA

[ota-meshi]

Hmm... I've considered it a bit, but it can be difficult.
It's difficult to create a temporary scope if it have the following script.

export let isOpen = false;
export let id: string | undefined = undefined;

$: a = !isOpen/*NG*/ && id

https://typescript-eslint.io/play/#ts=4.8.3&sourceType=module&code=KYDwDg9gTgLgBAG2PAlgZwPJmAOzgXjgDMBDBNYAbgChRJZFk4UATALjjRihRwHM4AHzgBXHC2BFewFgVHjJ0ljWoASDiTkBCdFlwB6AFQA5AOKH9cAGRXmLakA&eslintrc=N4KABGBEBOCuA2BTAzpAXGUEKQAIBcBPABxQGNoBLY-AWhXkoDt8B6Jge1tiacTJTIAhtEK0yHJgBNK+SpPRRE0aB2iRwYAL4gtQA&tsconfig=N4KABGBEDGD2C2AHAlgGwKYCcDyiAuysAdgM6QBcYoEEkJemy0eAcgK6qoDCAFutAGsylBm3TgwAXxCSgA

[mpiorowski]

Funny thing is, the typescript evalute isOpen variable correctly as boolean, not true / false, and still eslint throws warning ;p

[mpiorowski]

@ota-meshi and the other funny thing is, this condition works great when You use one of the variables, isOpen or id :D No warning then (logically it should also throw warning). BUT when You add the "&&" then the magic starts happening :D