chore(eslint): update eslint no-unused-vars rules

[Alfred-Skyblue]

We have excluded the no-unused-vars rule for TypeScript (.ts) files in our existing ESLint configuration, as TypeScript inherently checks for unused variables. However, if we don't configure this rule, ESLint won't perform the no-unused-vars check for TypeScript files. Nevertheless, we do need to enable this rule for JavaScript (.js) files to ensure that variables defined in JavaScript files are also being utilized.

-    'no-unused-vars': [
-      'error',
-      // we are only using this rule to check for unused arguments since TS
-      // catches unused variables but not args.
-      { varsIgnorePattern: '.*', args: 'none' }
-    ],

+    {
+      files: ['*.js'],
+      rules: {
+        // We only do `no-unused-vars` checks for js files, TS files are checked by TypeScript itself.
+        'no-unused-vars': ['error', { vars: 'all', args: 'none' }]
+      }
+    },

[github-actions]

Size Report

Bundles

File	Size	Gzip	Brotli
runtime-dom.global.prod.js	85.8 kB	32.6 kB	29.5 kB
vue.global.prod.js	132 kB	49.3 kB	44.3 kB

Usages

Name	Size	Gzip	Brotli
createApp	47.9 kB	18.8 kB	17.2 kB
createSSRApp	50.6 kB	19.9 kB	18.2 kB
defineCustomElement	50.3 kB	19.6 kB	17.9 kB
overall	61.2 kB	23.7 kB	21.6 kB

[sxzz]

Thanks for your contribution, but we don't think this change is necessary. Keeping both ESLint and TypeScript at the same time obviously won't affect anything, but it can better alert us to problems in the code.

[Alfred-Skyblue]

However, it override the inspection of JS files, causing unused imports in JS not to trigger errors. Additionally, this rule doesn't take effect within TS files. As a result, unused imports readFileSync in our build.js are not being flagged as errors.

[sxzz]

Then we need to lint both JS and TS files.

[Alfred-Skyblue]

In our current ESLint rules, we have enabled varsIgnorePattern: '.*', which effectively suppresses warnings for all unused variables, and args: 'none', which also suppresses warnings for all unused function parameters. In practice, these two configurations completely disable their respective functionalities. Enabling them would result in numerous errors in TypeScript files, as demonstrated below:

Based on the above, I believe we should only apply these checks to JavaScript files.