chore: release LWC v9 (#5635)

* chore: bump meriyah to v7 (#5626)

* build(deps): bump meriyah from 5.0.0 to 7.0.0

Bumps [meriyah](https://github.com/meriyah/meriyah) from 5.0.0 to 7.0.0.
- [Release notes](https://github.com/meriyah/meriyah/releases)
- [Changelog](https://github.com/meriyah/meriyah/blob/main/CHANGELOG.md)
- [Commits](meriyah/meriyah@v5.0.0...v7.0.0)

---
updated-dependencies:
- dependency-name: meriyah
  dependency-version: 7.0.0
  dependency-type: direct:production
  update-type: version-update:semver-major
...

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

* chore: fix version bump errors

---------

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

* feat(dist): publish packages as ESM rather than CJS @W-20496487 (#5639)

* feat: change packages to type: module

* chore: don't lint .cjs files

we don't use them

* chore: convert `module.exports` to `export default`

* chore: replace `__dirname` with `import.meta.dirname`

* chore: use .cjs extension

* chore: rename test command to match package

* revert(wdio): change back to commonjs

* chore: convert script to esm

* chore: change `main` entrypoint from CJS to ESM

* fix(esm): misc changes to support ESM-first

* fix: still use CJS for bundling

* feat: add package.json `exports`

* chore(deps): bump typescript to v6 (#5637)

* chore: enforce node v20 via `engines.node` @W-20496487 (#5636)

* chore(scripts): add engines.node to package.json validation

* chore(package.json): add engines.node to packages

* chore(engines): downgrade node to lowest version that works

* chore(engines): downgrade node to lowest version that works

* chore(engines): remove useless engines from root package.json

* chore(deps): bump deps

* chore: revert package.json `exports`

breaks vitest and I don't want to spend any more time on this

* test: update snapshots

* oops

* test: update snapshots

* test(perf): update perf-benchmarks to esm

* docs: switch to ESM

* chore: fix import

* chore(deps): revert bumps

* oops

* test: update TS version

* chore: prefer `node:` protocol (#5649)

* chore: replace duped issue number with open issue

* chore: remove completed TODOs

* feat(ts): use const to infer wire generics

* test(types): fix tests broken by const inference

* feat(compiler): rename experimentalDynamicComponent to dynamicImports (#5651)

* feat: deprecate engine-server (#5654)

* feat: remove engine-server from `lwc` barrel

* chore: mark engine-server as private

* test(ssr): move fixtures from engine-server to ssr-compiler

* chore: fix deps again hopefully

* test(wtr): remove broken tests

feature was never implemented

* chore(deps): pin so ts version stops breaking test

* chore: bump version to v8.27.0

* chore: minor TS adjustments @W-20496487 (#5647)

* chore(types): fiddle with types

I enabled `isolatedDeclarations` and fixed everything that made sense.
Fully enabling the flag requires creating explicit types for the error info objects in `@lwc/errors`,
which would be tedious, so I skipped that and disabled the flag.

I enabled `isolatedModules` and fixed everything that made sense.
We can't use `const enum` with isolated modules, but we like them because they minify cleanly,
so I skipped that and disabled the flag.

I enabled `erasableSyntaxOnly` and fixed everything that made sense.
We can't use `const enum` with isolated modules, but we like them because they minify cleanly,
so I skipped that and disabled the flag.
(I did replace our regular `enum` with objects.)

* test: fix TS version assertion

* chore: fix import

* feat(babel-plugin-component): remove import dedupe (#5650)

* feat: remove import dedupe

it gets done at the rollup level

* test(babel-plugin-component): update fixtures for no dedupe

* feat(playground): allow arbitrary port

* test(rollup): validate preserved import dedupe

* Apply suggestion from @wjhsf

* test(compiler): add import non-dedupe test

* chore: oops a comma

* Revert "feat: deprecate engine-server (#5654)"

This reverts commit 9260671.

* chore: revert change so file stays tree-shakeable

* chore: remove CJS hack

bundlers should be able to handle it by now

and if not, we're ESM-first!

* test(lwc): remove remnant of jest

* chore(deps): dependency treadmill

* Reapply "feat: deprecate engine-server (#5654)"

This reverts commit 4d9ba66.

* feat(wire): update type definition to make invalid config more obvious (#5660)

* feat(wire): make type def more helpful but less complete

Previously, `@wire(adapter,{config:value})` with an invalid `value`
resulted in a confusing error reported on `adapter`, because the function
inferred the config type and derived the adapter type.
Now the function infers the adapter type and derives the config type.
As a result, an invalid `value` correctly reports an error on `value`.
It does so by augmenting the config with the $reactive prop strings that
are available. However, due to recursive types, this list is potentially
infinite. To provide utility but mitigate this, only top-level props are
validated. Any chained property access (`$nested.prop`) validates that
the top-level prop is an object, but allows any nested props, even if
they are actually invalid.

* feat(decorators): always throw helpful error

* feat(wire): handle quirky edge case

* test(wire): split wire types test into multiple files

* test(types): update tests for @wire on methods

* test(types): update tests for @wire on getters

* test(types): update tests for @wire on setters

* feat(wire): omit LightningElement methods from config type

* fix(types): exclude `constructor` from wire reactive config expansions

* fix(types): exclude functions from nested property chain unless they have props

* test(decorators): message is thrown in prod, too

* chore(wire): update jsdoc with caveats

* chore(wire): update jsdoc with caveats and examples

* docs(wire): doc feedback

* chore: v8.28.0

* chore(deps): dependency treadmill

---------

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: James Tu <jmsjtu@gmail.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Author: 3 people

commitlint.config.js

@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: MIT
  * For full license text, see the LICENSE file in the repo root or https://opensource.org/licenses/MIT
  */
-module.exports = {
+export default {
     rules: {
         'body-leading-blank': [1, 'always'],
         'footer-leading-blank': [1, 'always'],

eslint.config.mjs

@@ -189,7 +189,7 @@ export default tseslint.config(
         },
     },
     {
-        files: ['**/*.js', '**/*.mjs', '**/*.cjs'],
+        files: ['**/*.js', '**/*.mjs'],
         ...tseslint.configs.disableTypeChecked,
     },
 

package.json

@@ -7,6 +7,7 @@
         "type": "git",
         "url": "https://github.com/salesforce/lwc.git"
     },
+    "type": "module",
     "scripts": {
         "prepare": "husky && yarn build",
         "lint": "eslint . --cache",
@@ -25,7 +26,7 @@
         "test:ci": "vitest run --coverage",
         "test:wtr": "nx test @lwc/integration-wtr",
         "test:hydration": "nx test:hydration @lwc/integration-wtr",
-        "test:integration": "nx sauce @lwc/integration-wdio",
+        "test:wdio": "nx sauce @lwc/integration-wdio",
         "test:performance": "nx test @lwc/perf-benchmarks",
         "test:performance:best": "nx test:best @lwc/perf-benchmarks",
         "test:performance:best:ci": "nx test:best:ci @lwc/perf-benchmarks",
@@ -49,7 +50,7 @@
         "@swc/core": "~1.15.10",
         "@swc/helpers": "~0.5.18",
         "@types/babel__core": "^7.20.5",
-        "@types/node": "^22.19.1",
+        "@types/node": "^22.19.5",
         "@vitest/coverage-v8": "4.0.17",
         "@vitest/eslint-plugin": "1.6.6",
         "@vitest/spy": "4.0.17",
@@ -72,7 +73,7 @@
         "rollup": "^4.55.2",
         "terser": "^5.46.0",
         "tslib": "^2.8.1",
-        "typescript": "5.8.2",
+        "typescript": "6.0.0-dev.20260112",
         "typescript-eslint": "8.53.1",
         "vitest": "4.0.17"
     },
@@ -87,9 +88,6 @@
         "packages/lwc",
         "playground"
     ],
-    "engines": {
-        "node": ">=10"
-    },
     "volta": {
         "node": "24.11.1",
         "yarn": "1.22.22"

packages/@lwc/aria-reflection/package.json

@@ -23,13 +23,17 @@
         "url": "https://github.com/salesforce/lwc/issues"
     },
     "license": "MIT",
+    "type": "module",
     "publishConfig": {
         "access": "public"
     },
+    "engines": {
+        "node": ">=16.6.0"
+    },
     "volta": {
         "extends": "../../../package.json"
     },
-    "main": "dist/index.cjs.js",
+    "main": "dist/index.js",
     "module": "dist/index.js",
     "types": "dist/index.d.ts",
     "files": [

packages/@lwc/aria-reflection/src/index.ts

@@ -57,7 +57,7 @@ const ARIA_PROPERTIES = [
     'ariaValueNow',
     'ariaValueText',
     'role',
-];
+] as const;
 
 for (const prop of ARIA_PROPERTIES) {
     const attribute = prop.replace(/^aria/, 'aria-').toLowerCase(); // e.g. ariaPosInSet => aria-posinset

packages/@lwc/babel-plugin-component/README.md

@@ -19,13 +19,17 @@
         "url": "https://github.com/salesforce/lwc/issues"
     },
     "license": "MIT",
+    "type": "module",
     "publishConfig": {
         "access": "public"
     },
+    "engines": {
+        "node": ">=16.6.0"
+    },
     "volta": {
         "extends": "../../../package.json"
     },
-    "main": "dist/index.cjs.js",
+    "main": "dist/index.js",
     "module": "dist/index.js",
     "types": "dist/index.d.ts",
     "files": [

packages/@lwc/babel-plugin-component/package.json

@@ -1,5 +1,6 @@
-import { registerDecorators as _registerDecorators, LightningElement, registerComponent as _registerComponent } from "lwc";
+import { registerDecorators as _registerDecorators } from "lwc";
 import _tmpl from "./test.html";
+import { LightningElement, registerComponent as _registerComponent } from 'lwc';
 class Test extends LightningElement {
   set first(value) {}
   get first() {}

packages/@lwc/babel-plugin-component/src/__tests__/fixtures/api-decorator/@api-setter-on-one-class-member-should-not-conflict-with-@api-getter-on-another/expected.js

@@ -1,5 +1,6 @@
-import { registerDecorators as _registerDecorators, LightningElement, registerComponent as _registerComponent } from "lwc";
+import { registerDecorators as _registerDecorators } from "lwc";
 import _tmpl from "./test.html";
+import { LightningElement, registerComponent as _registerComponent } from "lwc";
 class Test extends LightningElement {
   data;
   /*LWC compiler vX.X.X*/

packages/@lwc/babel-plugin-component/src/__tests__/fixtures/api-decorator/does-not-throw-error-if-property-name-is-data/expected.js

@@ -1,5 +1,6 @@
-import { registerDecorators as _registerDecorators, LightningElement, registerComponent as _registerComponent } from "lwc";
+import { registerDecorators as _registerDecorators } from "lwc";
 import _tmpl from "./test.html";
+import { LightningElement, registerComponent as _registerComponent } from "lwc";
 class Test extends LightningElement {
   ariaDescribedBy;
   /*LWC compiler vX.X.X*/