feat(virtual): Move to Typescript

packages/virtual/package.json

@@ -12,6 +12,9 @@
   "bugs": "https://github.com/rollup/rollup-plugin-virtual/issues",
   "main": "dist/index.js",
   "module": "dist/index.es.js",
+  "engines": {
+    "node": ">=8.0.0"
+  },
   "scripts": {
     "build": "rollup -c",
     "ci:coverage": "nyc pnpm run test && nyc report --reporter=text-lcov > coverage.lcov",
@@ -30,6 +33,7 @@
   },
   "files": [
     "dist",
+    "types",
     "README.md",
     "LICENSE"
   ],
@@ -46,12 +50,20 @@
   },
   "devDependencies": {
     "@rollup/plugin-node-resolve": "^8.4.0",
+    "@rollup/plugin-typescript": "^6.0.0",
     "rollup": "^2.23.0"
   },
+  "types": "types/index.d.ts",
   "ava": {
     "babel": {
       "compileEnhancements": false
     },
+    "extensions": [
+      "ts"
+    ],
+    "require": [
+      "ts-node/register"
+    ],
     "files": [
       "!**/fixtures/**",
       "!**/helpers/**",

packages/virtual/rollup.config.js

@@ -1,10 +1,11 @@
 import resolve from '@rollup/plugin-node-resolve';
+import typescript from '@rollup/plugin-typescript';
 
 import pkg from './package.json';
 
 export default {
-  input: 'src/index.js',
-  plugins: [resolve()],
+  input: 'src/index.ts',
+  plugins: [resolve(), typescript()],
   external: ['path'],
   output: [
     { format: 'cjs', file: pkg.main, exports: 'auto' },

packages/virtual/src/index.ts

@@ -0,0 +1,43 @@
+import * as path from 'path';
+
+import { Plugin } from 'rollup';
+
+import { RollupVirtualOptions } from '../';
+
+const PREFIX = `\0virtual:`;
+
+export default function virtual(modules: RollupVirtualOptions): Plugin {
+  const resolvedIds = new Map<string, string>();
+
+  Object.keys(modules).forEach((id) => {
+    resolvedIds.set(path.resolve(id), modules[id]);
+  });
+
+  return {
+    name: 'virtual',
+
+    resolveId(id, importer) {
+      if (id in modules) return PREFIX + id;
+
+      if (importer) {
+        const importerNoPrefix = importer.startsWith(PREFIX)
+          ? importer.slice(PREFIX.length)
+          : importer;
+        const resolved = path.resolve(path.dirname(importerNoPrefix), id);
+        if (resolvedIds.has(resolved)) return PREFIX + resolved;
+      }
+
+      return null;
+    },
+
+    load(id) {
+      if (id.startsWith(PREFIX)) {
+        const idNoPrefix = id.slice(PREFIX.length);
+
+        return idNoPrefix in modules ? modules[idNoPrefix] : resolvedIds.get(idNoPrefix);
+      }
+
+      return null;
+    }
+  };
+}

packages/virtual/tsconfig.json

@@ -0,0 +1,4 @@
+{
+  "extends": "../../tsconfig.base.json",
+  "include": ["src/**/*", "types/**/*"]
+}

packages/virtual/types/index.d.ts

@@ -0,0 +1,10 @@
+import { Plugin } from 'rollup';
+
+export interface RollupVirtualOptions {
+  [id: string]: string;
+}
+
+/**
+ * A Rollup plugin which loads virtual modules from memory.
+ */
+export default function virtual(modules: RollupVirtualOptions): Plugin;