build(deps-dev): bump @eslint/js from 9.39.2 to 10.0.1 (#5709)

* build(deps-dev): bump @eslint/js from 9.39.2 to 10.0.1

Bumps [@eslint/js](https://github.com/eslint/eslint/tree/HEAD/packages/js) from 9.39.2 to 10.0.1.
- [Release notes](https://github.com/eslint/eslint/releases)
- [Commits](https://github.com/eslint/eslint/commits/HEAD/packages/js)

---
updated-dependencies:
- dependency-name: "@eslint/js"
  dependency-version: 10.0.1
  dependency-type: direct:development
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

* chore(lint): fix new errors from eslint 10

* fix(test-utils): repair overzealous optimization

---------

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: Will Harney <wharney@salesforce.com>

Author: dependabot[bot]

package.json

@@ -37,7 +37,7 @@
     },
     "devDependencies": {
         "@commitlint/cli": "^20.4.2",
-        "@eslint/js": "9.39.2",
+        "@eslint/js": "10.0.1",
         "@lwc/eslint-plugin-lwc-internal": "link:./scripts/eslint-plugin",
         "@lwc/test-utils-lwc-internals": "link:./scripts/test-utils",
         "@nx/js": "22.5.3",

packages/@lwc/engine-core/src/framework/api.ts

@@ -379,21 +379,20 @@ function c(
     }
 
     const { key, slotAssignment } = data;
-    let elm, aChildren, vm;
     const vnode: VCustomElement = {
         type: VNodeType.CustomElement,
         sel,
         data,
         children,
-        elm,
+        elm: undefined,
         key,
         slotAssignment,
 
         ctor: Ctor,
         owner: vmBeingRendered,
         mode: 'open', // TODO [#1294]: this should be defined in Ctor
-        aChildren,
-        vm,
+        aChildren: undefined,
+        vm: undefined,
     };
     addVNodeToChildLWC(vnode);
 
@@ -519,26 +518,24 @@ function f(items: ReadonlyArray<VNodes> | VNodes): VNodes {
 
 // [t]ext node
 function t(text: string): VText {
-    let key, elm;
     return {
         type: VNodeType.Text,
         sel: '__text__',
         text,
-        elm,
-        key,
+        elm: undefined,
+        key: undefined,
         owner: getVMBeingRendered()!,
     };
 }
 
 // [co]mment node
 function co(text: string): VComment {
-    let elm, key;
     return {
         type: VNodeType.Comment,
         sel: '__comment__',
         text,
-        elm,
-        key,
+        elm: undefined,
+        key: undefined,
         owner: getVMBeingRendered()!,
     };
 }

packages/@lwc/ssr-compiler/src/compile-js/generate-markup.ts

@@ -137,14 +137,13 @@ export function addGenerateMarkupFunction(
     const defaultTagName = b.literal(tagName);
     const classIdentifier = b.identifier(state.lwcClassName!);
 
-    let exposeTemplateBlock: IfStatement | null = null;
     const defaultTmplPath = `./${pathParse(filename).name}.html`;
     const tmplVar = b.identifier('__lwcTmpl');
     program.body.unshift(bImportDeclaration({ default: tmplVar.name }, defaultTmplPath));
     program.body.unshift(
         bImportDeclaration({ SYMBOL__DEFAULT_TEMPLATE: '__SYMBOL__DEFAULT_TEMPLATE' })
     );
-    exposeTemplateBlock = bExposeTemplate(tmplVar, classIdentifier);
+    const exposeTemplateBlock = bExposeTemplate(tmplVar, classIdentifier);
 
     // If no wire adapters are detected on the component, we don't bother injecting the wire-related code.
     let connectWireAdapterCode: Statement[] = [];

packages/@lwc/ssr-runtime/src/context.ts

@@ -80,6 +80,7 @@ export function connectContext(le: LightningElement) {
         }
     } catch (err: any) {
         if (process.env.NODE_ENV !== 'production') {
+            // eslint-disable-next-line preserve-caught-error
             throw new Error(
                 `Attempted to connect to trusted context but received the following error: ${
                     err.message

packages/@lwc/style-compiler/src/transform.ts

@@ -82,6 +82,7 @@ export function transform(
     } catch (error) {
         if (errorRecoveryMode && error instanceof postcss.CssSyntaxError) {
             ctx.errors.push(error);
+            // eslint-disable-next-line preserve-caught-error
             throw AggregateError(ctx.errors);
         } else {
             throw error;

packages/@lwc/template-compiler/src/codegen/codegen.ts

@@ -782,7 +782,7 @@ export default class CodeGen {
                         this.isSyntheticShadow && (isIdOrIdRef || isScopedFragmentRef);
 
                     if (isExpression(value) || isSvgHref || needsScoping) {
-                        let partToken = '';
+                        let partToken: string;
                         if (name === 'style') {
                             partToken = `${STATIC_PART_TOKEN_ID.STYLE}${partId}`;
                             databag.push(

packages/@lwc/template-compiler/src/parser/expression.ts

@@ -170,9 +170,7 @@ export function parseIdentifier(
     source: string,
     location: SourceLocation
 ): Identifier {
-    let isValid = true;
-
-    isValid = isIdentifierStart(source.charCodeAt(0));
+    let isValid = isIdentifierStart(source.charCodeAt(0));
     for (let i = 1; i < source.length && isValid; i++) {
         isValid = isIdentifierChar(source.charCodeAt(i));
     }

packages/@lwc/template-compiler/src/shared/renderer-hooks.ts

@@ -62,9 +62,8 @@ function shouldAddCustomRenderer(element: BaseElement, state: State): boolean {
 
     const { attributes, directives } = element;
     if (directives.length) {
-        let directiveMatched = false;
         // If any directives require custom renderer
-        directiveMatched = directives.some((dir) => {
+        const directiveMatched = directives.some((dir) => {
             return state.crDirectives.has(ElementDirectiveName[dir.name]);
         });
         if (directiveMatched) {

scripts/test-utils/format-html.ts

@@ -19,7 +19,6 @@ import { HTML_NAMESPACE, isVoidElement } from '@lwc/shared';
 export function formatHTML(src: string): string {
     let res = '';
     let pos = 0;
-    let start = pos;
 
     let depth = 0;
 
@@ -46,7 +45,7 @@ export function formatHTML(src: string): string {
                     res += getPadding() + textContent + '\n';
                     depth--;
                     res += getPadding() + '</style>' + '\n';
-                    start = pos = pos + wholeMatch.length;
+                    pos = pos + wholeMatch.length;
                     continue;
                 }
             }
@@ -58,7 +57,7 @@ export function formatHTML(src: string): string {
                 src.charAt(pos + 2) === '-' &&
                 src.charAt(pos + 3) === '-';
 
-            start = pos;
+            const start = pos;
             while (src.charAt(pos++) !== '>') {
                 // Keep advancing until consuming the closing tag.
             }
@@ -88,7 +87,7 @@ export function formatHTML(src: string): string {
         }
 
         // Consume text content.
-        start = pos;
+        const start = pos;
         while (src.charAt(pos) !== '<' && pos < src.length) {
             pos++;
         }

scripts/test-utils/swap-lwc-style-for-style.ts

@@ -25,7 +25,7 @@ export function swapLwcStyleForStyleTag(src: string): string {
     // ([leading whitespace])(<style (id="(text)")...>...</style>)
     const styleCapture = /(\s*)(<style [^>]*(id="([^"]+)" ?)[^>]*>.*?<\/style>)/s;
     const capturedStyleTags: StyleTagInfo[] = [];
-    let styleTagMatch: RegExpExecArray | null = null;
+    let styleTagMatch: RegExpExecArray | null;
 
     // Find all <style> tags with an id, remove id attrs, capture information for later
     // replacement of <lwc-style> tags. The length of the `modifiedSrc` string will be
@@ -55,7 +55,7 @@ export function swapLwcStyleForStyleTag(src: string): string {
     const idToStyleTag = Object.fromEntries(
         capturedStyleTags.map((styleTagInfo) => [styleTagInfo.styleId, styleTagInfo])
     );
-    let lwcStyleTagMatch: RegExpExecArray | null = null;
+    let lwcStyleTagMatch: RegExpExecArray | null;
 
     // Find all <lwc-style> tags and replace them with corresponding <style> tags captured earlier.
     // The length of the `modifiedSrc` string will be changing as <style> tags are modified, so we