Build: Skip running ESLint on Node.js 0.x

ESLint 3.0 drops support for Node.js older than 4.x. To be able to update
to this version and yet not block our contributors from building jQuery
on older Node.js (at least until it's supported by upstream) this commit
makes ESLint skipped on older Node; a proper message is displayed then.

Fixes gh-3222

Gruntfile.js

@@ -14,9 +14,14 @@ module.exports = function( grunt ) {
 
 	var fs = require( "fs" ),
 		gzip = require( "gzip-js" ),
+		oldNode = /^v0\./.test( process.version );
 
-		// Skip jsdom-related tests in Node.js 0.10 & 0.12
-		runJsdomTests = !/^v0/.test( process.version );
+	// Support: Node.js <4
+	// Skip running tasks that dropped support for Node.js 0.10 & 0.12
+	// in those Node versions.
+	function runIfNewNode( task ) {
+		return oldNode ? "print_old_node_message:" + task : task;
+	}
 
 	if ( !grunt.option( "filename" ) ) {
 		grunt.option( "filename", "jquery.js" );
@@ -176,33 +181,50 @@ module.exports = function( grunt ) {
 	} );
 
 	// Load grunt tasks from NPM packages
-	require( "load-grunt-tasks" )( grunt );
+	// Support: Node.js <4
+	// Don't load the eslint task in old Node.js, it won't parse.
+	require( "load-grunt-tasks" )( grunt, {
+		pattern: oldNode ? [ "grunt-*", "!grunt-eslint" ] : [ "grunt-*" ]
+	} );
 
 	// Integrate jQuery specific tasks
 	grunt.loadTasks( "build/tasks" );
 
-	grunt.registerTask( "lint", [ "jsonlint", "eslint:all" ] );
+	grunt.registerTask( "print_old_node_message", function() {
+		var task = [].slice.call( arguments ).join( ":" );
+		grunt.log.writeln( "Old Node.js detected, running the task \"" + task + "\" skipped..." );
+	} );
 
-	// Don't run Node-related tests in Node.js < 1.0.0 as they require an old
-	// jsdom version that needs compiling, making it harder for people to compile
-	// jQuery on Windows. (see gh-2519)
-	grunt.registerTask( "test_fast", runJsdomTests ? [ "node_smoke_tests" ] : [] );
+	grunt.registerTask( "lint", [
+		"jsonlint",
+		runIfNewNode( "eslint:all" )
+	] );
+
+	grunt.registerTask( "test_fast", [ runIfNewNode( "node_smoke_tests" ) ] );
 
 	grunt.registerTask( "test", [ "test_fast" ].concat(
-		runJsdomTests ? [ "promises_aplus_tests" ] : []
+		[ runIfNewNode( "promises_aplus_tests" ) ]
 	) );
 
 	// Short list as a high frequency watch task
 	grunt.registerTask( "dev", [
 			"build:*:*",
-			"newer:eslint:dev",
+			runIfNewNode( "newer:eslint:dev" ),
 			"uglify",
 			"remove_map_comment",
 			"dist:*"
 		]
 	);
 
-	grunt.registerTask( "default", [ "dev", "eslint:dist", "test_fast", "compare_size" ] );
-
-	grunt.registerTask( "precommit_lint", [ "newer:jsonlint", "newer:eslint:all" ] );
+	grunt.registerTask( "default", [
+		"dev",
+		runIfNewNode( "eslint:dist" ),
+		"test_fast",
+		"compare_size"
+	] );
+
+	grunt.registerTask( "precommit_lint", [
+		"newer:jsonlint",
+		runIfNewNode( "newer:eslint:all" )
+	] );
 };