chore: ensure all exported files have a consistent filename

CHANGELOG.md

@@ -15,6 +15,8 @@
 ### Chore & Maintenance
 
 - `[*]` Avoid anonymous default exports ([#12313](https://github.com/facebook/jest/pull/12313))
+- `[@jest/core]` Use `index.ts` instead of `jest.ts` as main export ([#12329](https://github.com/facebook/jest/pull/12329))
+- `[jest]` Use `index.ts` instead of `jest.ts` as main export ([#12329](https://github.com/facebook/jest/pull/12329))
 
 ### Performance
 

packages/jest-core/package.json

@@ -2,12 +2,12 @@
   "name": "@jest/core",
   "description": "Delightful JavaScript Testing.",
   "version": "27.5.0",
-  "main": "./build/jest.js",
-  "types": "./build/jest.d.ts",
+  "main": "./build/index.js",
+  "types": "./build/index.d.ts",
   "exports": {
     ".": {
-      "types": "./build/jest.d.ts",
-      "default": "./build/jest.js"
+      "types": "./build/index.d.ts",
+      "default": "./build/index.js"
     },
     "./package.json": "./package.json"
   },

packages/jest/package.json

@@ -2,12 +2,12 @@
   "name": "jest",
   "description": "Delightful JavaScript Testing.",
   "version": "27.5.0",
-  "main": "./build/jest.js",
-  "types": "./build/jest.d.ts",
+  "main": "./build/index.js",
+  "types": "./build/index.d.ts",
   "exports": {
     ".": {
-      "types": "./build/jest.d.ts",
-      "default": "./build/jest.js"
+      "types": "./build/index.d.ts",
+      "default": "./build/index.js"
     },
     "./package.json": "./package.json",
     "./bin/jest": "./bin/jest.js"

scripts/buildUtils.js

@@ -31,16 +31,19 @@ module.exports.getPackages = function getPackages() {
   return packages.map(packageDir => {
     const pkg = readPkg({cwd: packageDir});
 
-    assert.ok(pkg.engines, `Engine requirement in ${pkg.name} should exist`);
+    assert.ok(pkg.engines, `Engine requirement in "${pkg.name}" should exist`);
 
     assert.strictEqual(
       pkg.engines.node,
       // TODO: remove special casing for Jest 28
       pkg.name === 'jest-worker' ? '>= 10.13.0' : nodeEngineRequirement,
-      `Engine requirement in ${pkg.name} should match root`,
+      `Engine requirement in "${pkg.name}" should match root`,
     );
 
-    assert.ok(pkg.exports, `Package ${pkg.name} is missing \`exports\` field`);
+    assert.ok(
+      pkg.exports,
+      `Package "${pkg.name}" is missing \`exports\` field`,
+    );
     assert.deepStrictEqual(
       pkg.exports,
       {
@@ -69,16 +72,35 @@ module.exports.getPackages = function getPackages() {
           ? {'./ConvertAnsi': './build/plugins/ConvertAnsi.js'}
           : {}),
       },
-      `Package ${pkg.name} does not export correct files`,
+      `Package "${pkg.name}" does not export correct files`,
     );
 
+    if (pkg.types) {
+      assert.strictEqual(
+        pkg.main,
+        './build/index.js',
+        `Package "${pkg.name}" should have "./build/index.js" as main`,
+      );
+      assert.strictEqual(
+        pkg.types,
+        './build/index.d.ts',
+        `Package "${pkg.name}" should have "./build/index.d.ts" as types`,
+      );
+    } else {
+      assert.strictEqual(
+        pkg.main,
+        './index.js',
+        `Package "${pkg.name}" should have "./index.js" as main`,
+      );
+    }
+
     if (pkg.bin) {
       Object.entries(pkg.bin).forEach(([binName, binPath]) => {
         const fullBinPath = path.resolve(packageDir, binPath);
 
         if (!fs.existsSync(fullBinPath)) {
           throw new Error(
-            `Binary in package ${pkg.name} with name "${binName}" at ${binPath} does not exist`,
+            `Binary in package "${pkg.name}" with name "${binName}" at ${binPath} does not exist`,
           );
         }
       });