support export statements properly (#2126)

- mangle & compress correctly with `toplevel`
- retain non-toplevel import/export
- parse & output `export { variable as name }`
- remove extraneous spaces from `beautify`


fixes #2038
fixes #2124

test/compress/export.js

@@ -0,0 +1,97 @@
+issue_2038_1: {
+    options = {
+        toplevel: true,
+        unused: true,
+    }
+    mangle = {
+        toplevel: true,
+    }
+    input: {
+        export var V = 1;
+        export let L = 2;
+        export const C = 3;
+    }
+    expect: {
+        export var V = 1;
+        export let L = 2;
+        export const C = 3;
+    }
+}
+
+issue_2038_2: {
+    options = {
+        toplevel: true,
+        unused: true,
+    }
+    mangle = {
+        toplevel: true,
+    }
+    input: {
+        let LET = 1;
+        const CONST = 2;
+        var VAR = 3;
+        export { LET, CONST, VAR };
+    }
+    expect: {
+        let a = 1;
+        const c = 2;
+        var n = 3;
+        export { a as LET, c as CONST, n as VAR };
+    }
+}
+
+issue_2124: {
+    options = {
+        unused: true,
+    }
+    input: {
+        {
+            export var V = 1;
+        }
+        {
+            export let L = 2;
+        }
+        {
+            export const C = 3;
+        }
+    }
+    expect: {
+        {
+            export var V = 1;
+        }
+        {
+            export let L = 2;
+        }
+        {
+            export const C = 3;
+        }
+    }
+}
+
+issue_2126: {
+    mangle = {
+        toplevel: true,
+    }
+    input: {
+        import { foo as bar, cat as dog } from "stuff";
+        console.log(bar, dog);
+        export { bar as qux };
+        export { dog };
+    }
+    expect: {
+        import { foo as o, cat as f } from "stuff";
+        console.log(o, f);
+        export { o as qux };
+        export { f as dog };
+    }
+}
+
+beautify: {
+    beautify = {
+        beautify: true,
+    }
+    input: {
+        export { A as B, C as D };
+    }
+    expect_exact: "export { A as B, C as D };"
+}

test/mocha/export.js

@@ -2,8 +2,7 @@ var assert = require("assert");
 var uglify = require("../node");
 
 describe("Export", function() {
-    it ("Should parse export directives", function() {
-
+    it("Should parse export directives", function() {
         var inputs = [
             ['export * from "a.js"', ['*'], "a.js"],
             ['export {A} from "a.js"', ['A'], "a.js"],
@@ -12,17 +11,17 @@ describe("Export", function() {
             ['export {A, B} from "a.js"', ['A', 'B'], "a.js"],
         ];
 
-        var test = function(code) {
+        function test(code) {
             return uglify.parse(code);
-        };
+        }
 
-        var extractNames = function(symbols) {
+        function extractNames(symbols) {
             var ret = [];
             for (var i = 0; i < symbols.length; i++) {
-                ret.push(symbols[i].name.name)
+                ret.push(symbols[i].foreign_name.name);
             }
             return ret;
-        };
+        }
 
         for (var i = 0; i < inputs.length; i++) {
             var ast = test(inputs[i][0]);
@@ -34,7 +33,7 @@ describe("Export", function() {
             assert(st instanceof uglify.AST_Export);
             var actualNames = extractNames(st.exported_names);
             assert.deepEqual(actualNames, names);
-            assert.equal(st.module_name.value, filename)
+            assert.equal(st.module_name.value, filename);
         }
-    })
-});
+    });
+});