support export statements (#4650)

lib/parse.js

@@ -844,6 +844,9 @@ function parse($TEXT, options) {
               case "await":
                 if (S.in_async) return simple_statement();
                 break;
+              case "export":
+                next();
+                return export_();
               case "import":
                 next();
                 return import_();
@@ -1275,6 +1278,115 @@ function parse($TEXT, options) {
         });
     }
 
+    function is_alias() {
+        return is("name") || is_identifier_string(S.token.value);
+    }
+
+    function export_() {
+        if (is("operator", "*")) {
+            next();
+            var alias = "*";
+            if (is("name", "as")) {
+                next();
+                if (!is_alias()) expect_token("name");
+                alias = S.token.value;
+                next();
+            }
+            expect_token("name", "from");
+            var path = S.token;
+            expect_token("string");
+            semicolon();
+            return new AST_ExportForeign({
+                aliases: [ alias ],
+                keys: [ "*" ],
+                path: path.value,
+                quote: path.quote,
+            });
+        }
+        if (is("punc", "{")) {
+            next();
+            var aliases = [];
+            var keys = [];
+            while (is_alias()) {
+                var key = S.token;
+                next();
+                keys.push(key);
+                if (is("name", "as")) {
+                    next();
+                    if (!is_alias()) expect_token("name");
+                    aliases.push(S.token.value);
+                    next();
+                } else {
+                    aliases.push(key.value);
+                }
+                if (!is("punc", "}")) expect(",");
+            }
+            expect("}");
+            if (is("name", "from")) {
+                next();
+                var path = S.token;
+                expect_token("string");
+                semicolon();
+                return new AST_ExportForeign({
+                    aliases: aliases,
+                    keys: keys.map(function(token) {
+                        return token.value;
+                    }),
+                    path: path.value,
+                    quote: path.quote,
+                });
+            }
+            semicolon();
+            return new AST_ExportReferences({
+                properties: keys.map(function(token, index) {
+                    if (!is_token(token, "name")) token_error(token, "Name expected");
+                    var sym = _make_symbol(AST_SymbolExport, token);
+                    sym.alias = aliases[index];
+                    return sym;
+                }),
+            });
+        }
+        if (is("keyword", "default")) {
+            next();
+            var body = expression();
+            semicolon();
+            return new AST_ExportDefault({ body: body });
+        }
+        return new AST_ExportDeclaration({ body: export_decl() });
+    }
+
+    var export_decl = embed_tokens(function() {
+        switch (S.token.value) {
+          case "async":
+            next();
+            expect_token("keyword", "function");
+            if (!is("operator", "*")) return function_(AST_AsyncDefun);
+            next();
+            return function_(AST_AsyncGeneratorDefun);
+          case "const":
+            next();
+            var node = const_();
+            semicolon();
+            return node;
+          case "function":
+            next();
+            if (!is("operator", "*")) return function_(AST_Defun);
+            next();
+            return function_(AST_GeneratorDefun);
+          case "let":
+            next();
+            var node = let_();
+            semicolon();
+            return node;
+          case "var":
+            next();
+            var node = var_();
+            semicolon();
+            return node;
+        }
+        unexpected();
+    });
+
     function import_() {
         var all = null;
         var def = as_symbol(AST_SymbolImport, true);
@@ -1288,7 +1400,7 @@ function parse($TEXT, options) {
             } else {
                 expect("{");
                 props = [];
-                while (is("name") || is_identifier_string(S.token.value)) {
+                while (is_alias()) {
                     var alias;
                     if (is_token(peek(), "name", "as")) {
                         var key = S.token.value;
@@ -1307,9 +1419,8 @@ function parse($TEXT, options) {
             }
         }
         if (all || def || props) expect_token("name", "from");
-        if (!is("string")) unexpected();
         var path = S.token;
-        next();
+        expect_token("string");
         semicolon();
         return new AST_Import({
             all: all,