Add a mostly hidden test.default that provides test

Our type definition uses ESM syntax; when using CJS with VSCode, the
auto-completion assumes the root is accessed through `require('ava').default`.
Placate VSCode by adding a mostly hidden default property on the root. This is
available through both CJS and ESM imports. We use a proxy so that we don't end
up with root.default.default.default chains.

Fixes #2539.

lib/create-chain.js

@@ -101,5 +101,28 @@ export default function createChain(fn, defaults, meta) {
 
 	root.meta = meta;
 
+	// Our type definition uses ESM syntax; when using CJS with VSCode, the
+	// auto-completion assumes the root is accessed through `require('ava').default`.
+	// Placate VSCode by adding a mostly hidden default property on the root.
+	// This is available through both CJS and ESM imports. We use a proxy so that
+	// we don't end up with root.default.default.default chains.
+	Object.defineProperty(root, 'default', {
+		configurable: false,
+		enumerable: false,
+		writable: false,
+		value: new Proxy(root, {
+			apply(target, thisArg, argumentsList) {
+				target.apply(thisArg, argumentsList);
+			},
+			get(target, prop) {
+				if (prop === 'default') {
+					throw new TypeError('Cannot access default.default');
+				}
+
+				return target[prop];
+			},
+		}),
+	});
+
 	return root;
 }

test/cjs-default/fixtures/package.json

@@ -0,0 +1,7 @@
+{
+	"ava": {
+		"files": [
+			"*.cjs"
+		]
+	}
+}

test/cjs-default/fixtures/test.cjs

@@ -0,0 +1,19 @@
+const test = require('ava');
+
+test.default('callable', t => { // eslint-disable-line ava/no-unknown-modifiers
+	t.pass();
+});
+
+test('no recursion', t => {
+	t.throws(() => test.default.default, {
+		name: 'TypeError',
+	});
+});
+
+test('not enumerable', t => {
+	t.false(Object.keys(test).includes('default'));
+});
+
+test('main export equals the ESM export', async t => {
+	t.is(test, (await import('ava')).default); // eslint-disable-line node/no-unsupported-features/es-syntax
+});

test/cjs-default/test.js

@@ -0,0 +1,7 @@
+import test from '@ava/test';
+
+import {fixture} from '../helpers/exec.js';
+
+test('ok', async t => {
+	await t.notThrowsAsync(fixture());
+});