@rollup/plugin-virtual: TS2349: This expression is not callable under modern "moduleResolution": "NodeNext"

Start with packages/virtual/package.json and packages/virtual/types/index.d.ts, then inspect the NodeNext import in the reported src/index.ts context. Verify the package's import and require type mappings by compiling the example with modern TypeScript settings; done means the default import is recognized as callable without TS2349.

• Rollup Plugin Name: @rollup/plugin-virtual
• Rollup Plugin Version: latest
• Rollup Version: latest
• Operating System (or Browser): macOS
• Node Version: v24.18.0
• Link to reproduction (⚠️ read below): I'm providing the exact type error context below. This is a static type resolution failure in TypeScript rather than a runtime execution bug.

Expected Behavior

When importing the plugin into a project using modern TypeScript settings ("moduleResolution": "NodeNext" or "Node16"), the default import should be recognized as a callable function:

import virtual from '@rollup/plugin-virtual';

export default {
  plugins: [
    virtual({ 'virtual-module': 'export default "hello";' })
  ]
};

Actual Behavior

The TypeScript compiler throws a compilation error preventing the build from running:

src/index.ts:59:13 - error TS2349: This expression is not callable.
  Type 'typeof import(".../node_modules/@rollup/plugin-virtual/types/index")' has no call signatures.

59             virtual({
               ~~~~~~~

Additional Information

The issue stems from a combination of the package layout configuration inside packages/virtual/package.json and packages/virtual/types/index.d.ts.

Why this happens

The plugin's package.json exports a single top-level typings statement:

"exports": {
  "types": "./types/index.d.ts",
  "import": "./dist/es/index.js",
  "default": "./dist/cjs/index.js"
}

Because the package does not explicitly include "type": "module", TypeScript's NodeNext engine treats ./types/index.d.ts as a CommonJS declaration file.

Under a CommonJS environment interpretation, TypeScript reads export default function virtual as an object property wrapper ({ default: function }) instead of a root-level callable default function export. As a result, the default import resolves to the module namespace object instead of the callable function, breaking execution under strict TypeScript configurations.

Fix

Provide separate type mappings for ESM and CJS hooks within exports so TypeScript evaluates them in their matching format context:

1. Copy packages/virtual/types/index.d.ts to a dedicated .d.mts version.
2. Update the exports configuration block in packages/virtual/package.json:

   "exports": {
     "import": {
       "types": "./types/index.d.mts",
       "default": "./dist/es/index.js"
     },
     "require": {
       "types": "./types/index.d.ts",
       "default": "./dist/cjs/index.js"
     }
   }