Evaluate ava.config.js scripts in current context

Fixes #2405.

lib/load-config.js

@@ -9,40 +9,15 @@ const NO_SUCH_FILE = Symbol('no ava.config.js file');
 const MISSING_DEFAULT_EXPORT = Symbol('missing default export');
 const EXPERIMENTS = new Set(['tryAssertion']);
 
-class LegacyCommonJsAccessError extends Error {
-	constructor(thing, fileForErrorMessage) {
-		super(`${thing} is not available in ${fileForErrorMessage}. Use a .cjs file instead`);
-		this.name = 'LegacyCommonJsAccessError';
-	}
-}
-
 // *Very* rudimentary support for loading ava.config.js files containing an `export default` statement.
-const evaluateJsConfig = (configFile, fileForErrorMessage) => {
+const evaluateJsConfig = configFile => {
 	const contents = fs.readFileSync(configFile, 'utf8');
 	const script = new vm.Script(`'use strict';(()=>{let __export__;\n${contents.replace(/export default/g, '__export__ =')};return __export__;})()`, {
 		filename: configFile,
 		lineOffset: -1
 	});
 	return {
-		default: script.runInNewContext({
-			console,
-			process,
-			get __dirname() {
-				throw new LegacyCommonJsAccessError('__dirname', fileForErrorMessage);
-			},
-			get __filename() {
-				throw new LegacyCommonJsAccessError('__filename', fileForErrorMessage);
-			},
-			get module() {
-				throw new LegacyCommonJsAccessError('module', fileForErrorMessage);
-			},
-			get exports() {
-				throw new LegacyCommonJsAccessError('exports', fileForErrorMessage);
-			},
-			get require() {
-				throw new LegacyCommonJsAccessError('require()', fileForErrorMessage);
-			}
-		})
+		default: script.runInThisContext()
 	};
 };
 
@@ -55,17 +30,13 @@ const loadJsConfig = ({projectDir, configFile = path.join(projectDir, 'ava.confi
 
 	let config;
 	try {
-		({default: config = MISSING_DEFAULT_EXPORT} = evaluateJsConfig(configFile, fileForErrorMessage));
+		({default: config = MISSING_DEFAULT_EXPORT} = evaluateJsConfig(configFile));
 	} catch (error) {
 		if (error.code === 'ENOENT') {
 			return null;
 		}
 
-		if (error.name === 'LegacyCommonJsAccessError') {
-			throw error;
-		} else {
-			throw Object.assign(new Error(`Error loading ${fileForErrorMessage}`), {parent: error});
-		}
+		throw Object.assign(new Error(`Error loading ${fileForErrorMessage}: ${error.message}`), {parent: error});
 	}
 
 	if (config === MISSING_DEFAULT_EXPORT) {

test/integration/config.js

@@ -3,7 +3,6 @@ const fs = require('fs');
 const path = require('path');
 const {test} = require('tap');
 const execa = require('execa');
-const figures = require('figures');
 const tempy = require('tempy');
 const {execCli} = require('../helper/cli');
 
@@ -13,7 +12,7 @@ test('formats errors from ava.config.js', t => {
 
 		const lines = stderr.split('\n');
 		t.is(lines[0], '');
-		t.is(lines[1], '  ' + figures.cross + ' Error loading ava.config.js');
+		t.match(lines[1], /Error loading ava\.config\.js:/);
 		t.is(lines[2], '');
 		t.match(lines[3], /ava\.config\.js/);
 		t.match(lines[4], /foo/);

test/load-config.js

@@ -80,7 +80,7 @@ test('loads config from factory function', t => {
 
 test('does not support require() inside config.js files', t => {
 	changeDir('require');
-	t.throws(loadConfig, /require\(\) is not available in ava\.config\.js\. Use a \.cjs file instead/);
+	t.throws(loadConfig, /Error loading ava\.config\.js: require is not defined/);
 	t.end();
 });