fix: get the right chunk name for preserve modules in Windows (#5625)

* add test

* remove Windows drive prefix

---------

Co-authored-by: Lukas Taegert-Atkinson <lukastaegert@users.noreply.github.com>

src/Chunk.ts

@@ -1069,9 +1069,15 @@ export default class Chunk {
 			? sanitizedId.slice(0, -extensionName.length)
 			: sanitizedId;
 		if (isAbsolute(idWithoutExtension)) {
-			return preserveModulesRoot && resolve(idWithoutExtension).startsWith(preserveModulesRoot)
-				? idWithoutExtension.slice(preserveModulesRoot.length).replace(/^[/\\]/, '')
-				: relative(this.inputBase, idWithoutExtension);
+			if (preserveModulesRoot && resolve(idWithoutExtension).startsWith(preserveModulesRoot)) {
+				return idWithoutExtension.slice(preserveModulesRoot.length).replace(/^[/\\]/, '');
+			} else {
+				// handle edge case in Windows
+				if (this.inputBase === '/' && !idWithoutExtension.startsWith('/')) {
+					return relative(this.inputBase, idWithoutExtension.replace(/^[a-zA-Z]:[/\\]/, '/'));
+				}
+				return relative(this.inputBase, idWithoutExtension);
+			}
 		} else {
 			return (
 				this.outputOptions.virtualDirname.replace(/\/$/, '') + '/' + basename(idWithoutExtension)

test/cli/samples/get-chunk-name/_config.js

@@ -0,0 +1,11 @@
+const assert = require('node:assert');
+module.exports = defineTest({
+	description: 'get right chunk name for preserve modules',
+	command: 'rollup -c',
+	result(code) {
+		assert.ok(
+			code.includes(`//→ ${__dirname.replace(/^(\/|[a-zA-Z]:\\)/, '').replace(/\\/g, '/')}/main.js`)
+		);
+		assert.ok(code.includes(`//→ sub.js`));
+	}
+});

test/cli/samples/get-chunk-name/main.js

@@ -0,0 +1,2 @@
+import sub from '/sub.js';
+assert.ok(sub);

test/cli/samples/get-chunk-name/rollup.config.mjs

@@ -0,0 +1,21 @@
+export default {
+	input: 'main.js',
+	output: {
+		format: 'es',
+		preserveModules: true
+	},
+	plugins: [
+		{
+			resolveId(id) {
+				if (id.endsWith('sub.js')) {
+					return id;
+				}
+			},
+			load(id) {
+				if (id.endsWith('sub.js')) {
+					return 'export default "sub.js url"';
+				}
+			}
+		}
+	]
+};