feat: implement harmony generators and yield

Uses #716's implementation and adds tests.

Fixes #716.

lib/ast.js

@@ -437,9 +437,10 @@ var AST_ArrowParametersOrSeq = DEFNODE("ArrowParametersOrSeq", "expressions", {
     }
 });
 
-var AST_Lambda = DEFNODE("Lambda", "name argnames uses_arguments", {
+var AST_Lambda = DEFNODE("Lambda", "name argnames uses_arguments isgenerator", {
     $documentation: "Base class for functions",
     $propdoc: {
+        isgenerator: "is generatorFn or not",
         name: "[AST_SymbolDeclaration?] the name of this function",
         argnames: "[AST_SymbolFunarg|AST_Destructuring|AST_Expansion*] array of function arguments, destructurings, or expanding arguments",
         uses_arguments: "[boolean/S] tells whether this function accesses the arguments array"

lib/output.js

@@ -226,6 +226,10 @@ function OutputStream(options) {
         OUTPUT += str;
     };
 
+    var star = function(){
+        print("*");
+    }
+
     var space = options.beautify ? function() {
         print(" ");
     } : function() {
@@ -343,6 +347,7 @@ function OutputStream(options) {
         should_break    : function() { return options.width && this.current_width() >= options.width },
         newline         : newline,
         print           : print,
+        star            : star,
         space           : space,
         comma           : comma,
         colon           : colon,
@@ -783,6 +788,9 @@ function OutputStream(options) {
         var self = this;
         if (!nokeyword) {
             output.print("function");
+            if (this.isgenerator) {
+                output.star();
+            }
             if (self.name) {
                 output.space();
             }
@@ -1141,8 +1149,13 @@ function OutputStream(options) {
         output.print(self.operator);
     });
     DEFPRINT(AST_Binary, function(self, output){
+        var isYield = (self.left.operator == "yield" || self.left.operator === "yield*");
         var op = self.operator;
+
+        isYield && output.print("(");
         self.left.print(output);
+        isYield && output.print(")");
+
         if (op[0] == ">" /* ">>" ">>>" ">" ">=" */
             && self.left instanceof AST_UnaryPostfix
             && self.left.operator == "--") {
@@ -1152,7 +1165,12 @@ function OutputStream(options) {
             // the space is optional depending on "beautify"
             output.space();
         }
+
+        isYield = (self.right.operator == "yield" || self.right.operator === "yield*");
+        isYield && output.print("(");
         output.print(op);
+        isYield && output.print(")");
+
         if ((op == "<" || op == "<<")
             && self.right instanceof AST_UnaryPrefix
             && self.right.operator == "!"

lib/parse.js

@@ -44,7 +44,7 @@
 
 "use strict";
 
-var KEYWORDS = 'break case catch class const continue debugger default delete do else extends finally for function if in instanceof new return switch throw try typeof var let void while with';
+var KEYWORDS = 'break case catch class const continue debugger default delete do else extends finally for function if in instanceof new return yield switch throw try typeof var let void while with';
 var KEYWORDS_ATOM = 'false null true';
 var RESERVED_WORDS = 'abstract boolean byte char double enum export final float goto implements import int interface long native package private protected public short static super synchronized this throws transient volatile yield'
     + " " + KEYWORDS_ATOM + " " + KEYWORDS;
@@ -68,6 +68,7 @@ var OPERATORS = makePredicate([
     "instanceof",
     "typeof",
     "new",
+    "yield",
     "void",
     "delete",
     "++",
@@ -627,6 +628,7 @@ var UNARY_PREFIX = makePredicate([
     "typeof",
     "void",
     "delete",
+    "yield",
     "--",
     "++",
     "!",
@@ -1050,6 +1052,11 @@ function parse($TEXT, options) {
         var start = S.token
 
         var in_statement = ctor === AST_Defun;
+        var isgenerator = is("operator", "*");
+        if (isgenerator) {
+          next();
+        }
+
         var name = is("name") ? as_symbol(in_statement ? AST_SymbolDefun : AST_SymbolLambda) : null;
         if (in_statement && !name)
             unexpected();
@@ -1059,6 +1066,7 @@ function parse($TEXT, options) {
         return new ctor({
             start : args.start,
             end   : body.end,
+            isgenerator: isgenerator,
             name  : name,
             argnames: args,
             body  : body
@@ -1716,6 +1724,10 @@ function parse($TEXT, options) {
         var start = S.token;
         if (is("operator") && UNARY_PREFIX(start.value)) {
             next();
+            if  (start.type === "operator" && start.value === "yield" && is("operator", "*")) {
+                start.value = "yield*";
+                next();
+            }
             handle_regexp();
             var ex = make_unary(AST_UnaryPrefix, start.value, maybe_unary(allow_calls));
             ex.start = start;

test/compress/harmony.js

@@ -321,3 +321,19 @@ regression_cannot_use_of: {
         foo();  /* Label statement missing? No prob. */
     }
 }
+
+generators: {
+    input: {
+        function* fn() {};
+    }
+    expect_exact: "function*fn(){}"
+}
+
+generators_yield: {
+    input: {
+      function* fn() {
+        yield remote();
+      }
+    }
+    expect_exact: "function*fn(){yield remote()}"
+}

test/parser.js

@@ -118,6 +118,17 @@ module.exports = function () {
     ok.equal(expanding_def.name.names[0].TYPE, 'SymbolVar');
     ok.equal(expanding_def.name.names[1].TYPE, 'Expansion');
     ok.equal(expanding_def.name.names[1].symbol.TYPE, 'SymbolVar');
+
+    // generators
+    var generators_def = UglifyJS.parse('function* fn() {}').body[0];
+    ok.equal(generators_def.isgenerator, true);
+
+    ok.throws(function () {
+        UglifyJS.parse('function* (){ }');
+    });
+
+    var generators_yield_def = UglifyJS.parse('function* fn() {\nyield remote();\}').body[0].body[0];
+    ok.equal(generators_yield_def.body.operator, 'yield');
 }
 
 // Run standalone