fix: stabilize chunk assignment across parallel file reads (#6362)

* fix: make chunk assignment and export naming deterministic (#5902)

Rollup stores parsed modules in a Map<string, Module> (modulesById).
With parallel file reads, modules are inserted in whichever order their
resolveId hooks complete, making iteration order non-deterministic across
builds. Two code paths depended on this order:

- Bundle.assignManualChunks iterated modulesById.values() directly, so
  a stateful manualChunks function produced different chunk assignments
  on different runs. Fix: sort modules alphabetically by ID before
  iterating.

- assignExportsToMangledNames and assignExportsToNames iterated the
  chunk exports Set in insertion order. Fix: sort exports before
  assigning aliases using a stable comparator: module ID → source
  declaration position → base name → export key → constructor name.
  Synthetic variables (NamespaceVariable etc.) have no source
  declaration and receive Number.MAX_SAFE_INTEGER as their position so
  they always sort after regular variables, preventing them from
  stealing natural export names in CJS/AMD/UMD formats.

Adds a regression test that builds the same graph twice with different
resolveId delay patterns and asserts identical chunk names, hashes, and
code. Updates five chunking-form snapshots whose previous expected
output reflected arbitrary insertion order rather than the new
deterministic sort (ES and System formats only).

* Add a regression test and refine the fix

* Remove unnecessary options in the test

* Also add a test with mangled exports

* Make sorting more stable

* Fix tests

---------

Co-authored-by: Sonu Kapoor <sonu@bitovi.com>
Co-authored-by: TrickyPi <530257315@qq.com>
Co-authored-by: Lukas Taegert-Atkinson <lukas.taegert-atkinson@tngtech.com>
Co-authored-by: Lukas Taegert-Atkinson <lukastaegert@users.noreply.github.com>

Author: 4 people

src/utils/exportNames.ts

@@ -1,14 +1,17 @@
 import type Variable from '../ast/variables/Variable';
-import RESERVED_NAMES from './RESERVED_NAMES';
 import { toBase64 } from './base64';
+import RESERVED_NAMES from './RESERVED_NAMES';
 
 export function assignExportsToMangledNames(
 	exports: ReadonlySet<Variable>,
 	exportsByName: Map<string, Variable>,
 	exportNamesByVariable: Map<Variable, string[]>
 ): void {
 	let nameIndex = 0;
-	for (const variable of exports) {
+	const sortedExports = [...exports].sort((a, b) =>
+		a.name < b.name ? -1 : a.name > b.name ? 1 : 0
+	);
+	for (const variable of sortedExports) {
 		let [exportName] = variable.name;
 		if (exportsByName.has(exportName)) {
 			do {

test/chunking-form/samples/dynamic-import-facade/_expected/es/generated-dynamic.js

@@ -10,4 +10,4 @@ var dynamic$1 = /*#__PURE__*/Object.freeze({
 	dynamic: dynamic
 });
 
-export { dep as a, dynamic$1 as b, dynamic as d };
+export { dynamic as a, dynamic$1 as b, dep as d };

test/chunking-form/samples/dynamic-import-facade/_expected/es/main2.js

@@ -1,3 +1,3 @@
-import { d as dynamic, a as dep } from './generated-dynamic.js';
+import { a as dynamic, d as dep } from './generated-dynamic.js';
 
 console.log('main2', dynamic, dep);

test/chunking-form/samples/dynamic-import-facade/_expected/system/generated-dynamic.js

@@ -5,10 +5,10 @@ System.register([], (function (exports) {
 
 			console.log('dep');
 
-			const dep = exports("a", 'dep');
+			const dep = exports("d", 'dep');
 
 			console.log('dynamic', dep);
-			const dynamic = exports("d", 'dynamic');
+			const dynamic = exports("a", 'dynamic');
 
 			var dynamic$1 = /*#__PURE__*/Object.freeze({
 				__proto__: null,

test/chunking-form/samples/dynamic-import-facade/_expected/system/main2.js

@@ -3,8 +3,8 @@ System.register(['./generated-dynamic.js'], (function () {
 	var dynamic, dep;
 	return {
 		setters: [function (module) {
-			dynamic = module.d;
-			dep = module.a;
+			dynamic = module.a;
+			dep = module.d;
 		}],
 		execute: (function () {
 

test/chunking-form/samples/manual-chunks-dynamic-facades/_expected/es/generated-dynamic.js

@@ -24,4 +24,4 @@ var dynamic1 = /*#__PURE__*/Object.freeze({
 	DYNAMIC_3: DYNAMIC_3
 });
 
-export { DEP as D, dynamic3 as a, dynamic1 as b, dynamic2 as d };
+export { DEP as D, dynamic2 as a, dynamic3 as b, dynamic1 as d };

test/chunking-form/samples/manual-chunks-dynamic-facades/_expected/es/main.js

@@ -1,5 +1,5 @@
 import { D as DEP } from './generated-dynamic.js';
 
-Promise.all([import('./generated-dynamic.js').then(function (n) { return n.b; }), import('./generated-dynamic.js').then(function (n) { return n.d; }), import('./generated-dynamic.js').then(function (n) { return n.a; })]).then(
+Promise.all([import('./generated-dynamic.js').then(function (n) { return n.d; }), import('./generated-dynamic.js').then(function (n) { return n.a; }), import('./generated-dynamic.js').then(function (n) { return n.b; })]).then(
 	results => console.log(results, DEP)
 );

test/chunking-form/samples/manual-chunks-dynamic-facades/_expected/system/generated-dynamic.js

@@ -11,15 +11,15 @@ System.register([], (function (exports) {
 				__proto__: null,
 				DYNAMIC_2: DYNAMIC_2
 			});
-			exports("d", dynamic2);
+			exports("a", dynamic2);
 
 			const DYNAMIC_3 = 'DYNAMIC_3';
 
 			var dynamic3 = /*#__PURE__*/Object.freeze({
 				__proto__: null,
 				DYNAMIC_3: DYNAMIC_3
 			});
-			exports("a", dynamic3);
+			exports("b", dynamic3);
 
 			const DYNAMIC_1 = 'DYNAMIC_1';
 
@@ -30,7 +30,7 @@ System.register([], (function (exports) {
 				DYNAMIC_2: DYNAMIC_2,
 				DYNAMIC_3: DYNAMIC_3
 			});
-			exports("b", dynamic1);
+			exports("d", dynamic1);
 
 		})
 	};

test/chunking-form/samples/manual-chunks-dynamic-facades/_expected/system/main.js

@@ -7,7 +7,7 @@ System.register(['./generated-dynamic.js'], (function (exports, module) {
 		}],
 		execute: (function () {
 
-			Promise.all([module.import('./generated-dynamic.js').then(function (n) { return n.b; }), module.import('./generated-dynamic.js').then(function (n) { return n.d; }), module.import('./generated-dynamic.js').then(function (n) { return n.a; })]).then(
+			Promise.all([module.import('./generated-dynamic.js').then(function (n) { return n.d; }), module.import('./generated-dynamic.js').then(function (n) { return n.a; }), module.import('./generated-dynamic.js').then(function (n) { return n.b; })]).then(
 				results => console.log(results, DEP)
 			);
 

test/chunking-form/samples/manual-chunks-dynamic-name-conflict/_expected/es/generated-dynamic.js

@@ -17,4 +17,4 @@ var dynamic1 = /*#__PURE__*/Object.freeze({
 	DYNAMIC_B: DYNAMIC_A
 });
 
-export { dynamic1 as a, dynamic2 as d };
+export { dynamic2 as a, dynamic1 as d };