v2.8.24

fixes #1922

README.md

@@ -11,9 +11,10 @@ There's also an
 Chrome and probably Safari).
 
 #### Note:
-- release versions of `uglify-js` only support ECMAScript 5 (ES5). If you wish to minify
-ES2015+ (ES6+) code then please use the [harmony](#harmony) development branch.
-- Node 7 has a known performance regression and runs `uglify-js` twice as slow.
+- `uglify-js` only supports ECMAScript 5 (ES5).
+- Support for `const` is [present but incomplete](#support-for-const), and may not be
+  transformed properly.
+- Those wishing to minify ES2015+ (ES6+) should use the `npm` package [**uglify-es**](https://github.com/mishoo/UglifyJS2/tree/harmony).
 
 Install
 -------
@@ -29,12 +30,6 @@ From NPM for programmatic use:
 
     npm install uglify-js
 
-From Git:
-
-    git clone git://github.com/mishoo/UglifyJS2.git
-    cd UglifyJS2
-    npm link .
-
 Usage
 -----
 
@@ -448,6 +443,11 @@ to set `true`; it's effectively a shortcut for `foo=true`).
 - `keep_infinity` -- default `false`. Pass `true` to prevent `Infinity` from
   being compressed into `1/0`, which may cause performance issues on Chrome.
 
+- `side_effects` -- default `false`. Pass `true` to potentially drop functions
+marked as "pure".  (A function is marked as "pure" via the comment annotation
+`/* @__PURE__ */` or `/* #__PURE__ */`)
+
+
 ### The `unsafe` option
 
 It enables some transformations that *might* break code logic in certain
@@ -983,19 +983,9 @@ The `source_map_options` (optional) can contain the following properties:
   [compressor]: http://lisperator.net/uglifyjs/compress
   [parser]: http://lisperator.net/uglifyjs/parser
 
-#### Harmony
+#### Support for `const`
 
-If you wish to use the experimental [harmony](https://github.com/mishoo/UglifyJS2/commits/harmony)
-branch to minify ES2015+ (ES6+) code please use the following in your `package.json` file:
-
-```
-"uglify-js": "git+https://github.com/mishoo/UglifyJS2.git#harmony"
-```
-
-or to directly install the experimental harmony version of uglify:
-
-```
-npm install --save-dev uglify-js@github:mishoo/UglifyJS2#harmony
-```
-
-See [#448](https://github.com/mishoo/UglifyJS2/issues/448) for additional details.
+`const` in `uglify-js@2.x` has function scope and as such behaves much like
+`var` - unlike `const` in ES2015 (ES6) which has block scope. It is recommended
+to avoid using `const` for this reason as it will have undefined behavior when
+run on an ES2015 compatible browser.

lib/compress.js

@@ -326,10 +326,14 @@ merge(Compressor.prototype, {
                     // So existing transformation rules can work on them.
                     node.argnames.forEach(function(arg, i) {
                         var d = arg.definition();
-                        d.fixed = function() {
-                            return iife.args[i] || make_node(AST_Undefined, iife);
-                        };
-                        mark(d, true);
+                        if (!node.uses_arguments && d.fixed === undefined) {
+                            d.fixed = function() {
+                                return iife.args[i] || make_node(AST_Undefined, iife);
+                            };
+                            mark(d, true);
+                        } else {
+                            d.fixed = false;
+                        }
                     });
                 }
                 if (node instanceof AST_If || node instanceof AST_DWLoop) {
@@ -414,7 +418,9 @@ merge(Compressor.prototype, {
 
         function reset_def(def) {
             def.escaped = false;
-            if (toplevel || !def.global || def.orig[0] instanceof AST_SymbolConst) {
+            if (def.scope.uses_eval) {
+                def.fixed = false;
+            } else if (toplevel || !def.global || def.orig[0] instanceof AST_SymbolConst) {
                 def.fixed = undefined;
             } else {
                 def.fixed = false;
@@ -440,6 +446,14 @@ merge(Compressor.prototype, {
         return fixed();
     });
 
+    function is_reference_const(ref) {
+        if (!(ref instanceof AST_SymbolRef)) return false;
+        var orig = ref.definition().orig;
+        for (var i = orig.length; --i >= 0;) {
+            if (orig[i] instanceof AST_SymbolConst) return true;
+        }
+    }
+
     function find_variable(compressor, name) {
         var scope, i = 0;
         while (scope = compressor.parent(i++)) {
@@ -1909,6 +1923,7 @@ merge(Compressor.prototype, {
                         && node instanceof AST_Assign
                         && node.operator == "="
                         && node.left instanceof AST_SymbolRef
+                        && !is_reference_const(node.left)
                         && scope === self) {
                         node.right.walk(tw);
                         return true;
@@ -3066,7 +3081,8 @@ merge(Compressor.prototype, {
             }
             if (left
                 && !(left instanceof AST_SymbolRef
-                    && left.definition().orig[0] instanceof AST_SymbolLambda)) {
+                    && (left.definition().orig[0] instanceof AST_SymbolLambda
+                        || is_reference_const(left)))) {
                 var parent, field;
                 var cdr = self.cdr;
                 while (true) {

package.json

@@ -4,7 +4,7 @@
   "homepage": "http://lisperator.net/uglifyjs",
   "author": "Mihai Bazon <mihai.bazon@gmail.com> (http://lisperator.net/)",
   "license": "BSD-2-Clause",
-  "version": "2.8.23",
+  "version": "2.8.24",
   "engines": {
     "node": ">=0.8.0"
   },

test/compress/collapse_vars.js

@@ -1592,3 +1592,49 @@ var_side_effects_3: {
     }
     expect_stdout: true
 }
+
+reassign_const_1: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        function f() {
+            const a = 1;
+            a = 2;
+            return a;
+        }
+        console.log(f());
+    }
+    expect: {
+        function f() {
+            const a = 1;
+            a = 2;
+            return a;
+        }
+        console.log(f());
+    }
+    expect_stdout: true
+}
+
+reassign_const_2: {
+    options = {
+        collapse_vars: true,
+    }
+    input: {
+        function f() {
+            const a = 1;
+            ++a;
+            return a;
+        }
+        console.log(f());
+    }
+    expect: {
+        function f() {
+            const a = 1;
+            ++a;
+            return a;
+        }
+        console.log(f());
+    }
+    expect_stdout: true
+}

test/compress/drop-unused.js

@@ -1064,3 +1064,28 @@ issue_1830_2: {
     }
     expect_stdout: "1"
 }
+
+reassign_const: {
+    options = {
+        cascade: true,
+        sequences: true,
+        side_effects: true,
+        unused: true,
+    }
+    input: {
+        function f() {
+            const a = 1;
+            a = 2;
+            return a;
+        }
+        console.log(f());
+    }
+    expect: {
+        function f() {
+            const a = 1;
+            return a = 2, a;
+        }
+        console.log(f());
+    }
+    expect_stdout: true
+}

test/compress/reduce_vars.js

@@ -41,22 +41,22 @@ reduce_vars: {
         var A = 1;
         (function() {
             console.log(-3);
-            console.log(-4);
+            console.log(A - 5);
         })();
         (function f1() {
             var a = 2;
-            console.log(-3);
+            console.log(a - 5);
             eval("console.log(a);");
         })();
         (function f2(eval) {
             var a = 2;
-            console.log(-3);
+            console.log(a - 5);
             eval("console.log(a);");
         })(eval);
         (function() {
             return "yes";
         })();
-        console.log(2);
+        console.log(A + 1);
     }
     expect_stdout: true
 }
@@ -1732,7 +1732,10 @@ redefine_arguments_3: {
         console.log(function() {
             var arguments;
             return typeof arguments;
-        }(), "number", "undefined");
+        }(), "number", function(x) {
+            var arguments = x;
+            return typeof arguments;
+        }());
     }
     expect_stdout: "object number undefined"
 }
@@ -2122,3 +2125,47 @@ issue_1865: {
     }
     expect_stdout: true
 }
+
+issue_1922_1: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        console.log(function(a) {
+            arguments[0] = 2;
+            return a;
+        }(1));
+    }
+    expect: {
+        console.log(function(a) {
+            arguments[0] = 2;
+            return a;
+        }(1));
+    }
+    expect_stdout: "2"
+}
+
+issue_1922_2: {
+    options = {
+        evaluate: true,
+        reduce_vars: true,
+        unused: true,
+    }
+    input: {
+        console.log(function() {
+            var a;
+            eval("a = 1");
+            return a;
+        }(1));
+    }
+    expect: {
+        console.log(function() {
+            var a;
+            eval("a = 1");
+            return a;
+        }(1));
+    }
+    expect_stdout: "1"
+}

test/compress/sequences.js

@@ -610,3 +610,27 @@ delete_seq_6: {
     }
     expect_stdout: true
 }
+
+reassign_const: {
+    options = {
+        cascade: true,
+        sequences: true,
+        side_effects: true,
+    }
+    input: {
+        function f() {
+            const a = 1;
+            a++;
+            return a;
+        }
+        console.log(f());
+    }
+    expect: {
+        function f() {
+            const a = 1;
+            return a++, a;
+        }
+        console.log(f());
+    }
+    expect_stdout: true
+}