`prefer-const` is reported when assignment occurs in different scope.

Tell us about your environment

Environment Info:

Node version: v16.7.0 npm version: v7.20.6 Local ESLint version: Not found Global ESLint version: Not found Operating System: linux 5.13.10-arch1-1

What parser (default, @babel/eslint-parser, @typescript-eslint/parser, etc.) are you using?

We’re using the @typescript-eslint/parser.

Please show your full configuration:

https://github.com/thenativeweb/eslint-config-es/blob/main/browser.js which extends https://github.com/thenativeweb/eslint-config-es/blob/main/node.js

What did you do? Please include the actual source code causing the issue, as well as the command that you used to run ESLint.

We’re shipping the new eslint version in our build tool roboter. After updating, we’ve encountered a couple of reported issues that hadn’t been reported before while linting one of our packages. We believe the prefer-const rule is reported falsely in the following case. Eslint is called by roboter. It uses the JS API as seen here.

const getBrokenUrls = async function ([...]): Promise<BrokenUrl[]> {
  
  [...]

  // eslint-disable-next-line no-constant-condition, @typescript-eslint/no-unnecessary-condition
  while (true) {
    
    [...]

    let page: Page;

    try {
      page = await getPage({ url: currentUrl });
    } catch {
      brokenUrls.push({ url: currentUrl, referrers: referrers[currentUrl] });
      onBrokenUrl({ url: currentUrl, referrers: referrers[currentUrl] });
      continue;
    }

    if (!currentUrl.startsWith(baseUrl)) {
      continue;
    }

    const externalUrls = getExternalUrlsFromPage({ page, baseUrl });

   [...]
};

What did you expect to happen?

The prefer-const rule should not apply to the file shown, as page is declared in a different scope than it is first assigned. The declaration of page can’t be moved into the try block without moving other statements into the block as well.

What actually happened? Please copy-paste the actual, raw output from ESLint.

Eslint reports the error: error 'page' is never reassigned. Use 'const' instead prefer-const.

Steps to reproduce this issue:

1. git clone [e-mail]:thenativeweb/thenativeweb-ux.git --branch dependabot/npm_and_yarn/roboter-12.0.0
2. cd thenativeweb-ux && npm install
3. npx roboter

Are you willing to submit a pull request to fix this bug?

Yes

[strangedev]

The documentation confirms your suspicion @mdjermanovic and further testing showed that the scope analysis works as expected when a valid version is used. Thank you for your help, your input has saved me a lot of time and frustration! 😊

[mdjermanovic]

I think that @typescript-eslint/parser doesn’t support ecmaVersion: "latest". and I’m guessing that it then falls back to analyzing scope as if it was ecmaVersion: "5" (without block scopes). Can you try with a number value?