Only fix `npm link` of AVA as necessary. (#827)

lib/fork.js

@@ -1,12 +1,23 @@
 'use strict';
 var childProcess = require('child_process');
 var path = require('path');
+var fs = require('fs');
 var objectAssign = require('object-assign');
 var Promise = require('bluebird');
 var debug = require('debug')('ava');
 var AvaError = require('./ava-error');
 var doSend = require('./send');
 
+var fixNpmLink = fs.realpathSync(__filename) !== __filename;
+
+if (fixNpmLink) {
+	// Workaround for breakage caused by https://github.com/nodejs/node/pull/5950
+	// Those changes will be reverted in https://github.com/nodejs/node/pull/6537
+
+	// Revert #815 and #827 when the above changes land in Node.js
+	console.warn('WARNING: `npm link ava` detected: This breaks NYC coverage on early versions of Node 6.\nSee https://github.com/sindresorhus/ava/pull/815');
+}
+
 var env = process.env;
 
 // ensure NODE_PATH paths are absolute
@@ -31,10 +42,13 @@ module.exports = function (file, opts) {
 		} : false
 	}, opts);
 
+	var ps;
+
+	if (fixNpmLink) {
 		// Workaround for breakage caused by https://github.com/nodejs/node/pull/5950
 		// Those changes will be reverted in https://github.com/nodejs/node/pull/6537
 
-	// Revert #815 when these changes land in Node.js
+		// Revert #815 and #827 when the above changes land in Node.js
 		var execArgv = process.execArgv;
 		var cwd = path.dirname(file);
 
@@ -57,11 +71,18 @@ module.exports = function (file, opts) {
 			JSON.stringify(opts)
 		]);
 
-	var ps = childProcess.spawn(process.execPath, args, {
+		ps = childProcess.spawn(process.execPath, args, {
 			cwd: cwd,
 			stdio: ['pipe', 'pipe', 'pipe', 'ipc'],
 			env: env
 		});
+	} else {
+		ps = childProcess.fork(path.join(__dirname, 'test-worker.js'), [JSON.stringify(opts)], {
+			cwd: path.dirname(file),
+			silent: true,
+			env: env
+		});
+	}
 
 	var relFile = path.relative('.', file);