v3.0.4

- preserve (re)assignment to `const` for runtime error
- suppress `cascade` on `const`, as runtime behaviour is ill-defined

README.md

@@ -7,7 +7,7 @@ UglifyJS is a JavaScript parser, minifier, compressor and beautifier toolkit.
 #### Note:
 - **`uglify-js@3.x` has a new API and CLI and is not backwards compatible with [`uglify-js@2.x`](https://github.com/mishoo/UglifyJS2/tree/v2.x)**.
 - **Documentation for UglifyJS `2.x` releases can be found [here](https://github.com/mishoo/UglifyJS2/tree/v2.x)**.
-- Release versions of `uglify-js` only support ECMAScript 5 (ES5). 
+- `uglify-js` only supports ECMAScript 5 (ES5).
 - Those wishing to minify
 ES2015+ (ES6+) should use the `npm` package [**uglify-es**](https://github.com/mishoo/UglifyJS2/tree/harmony).
 
@@ -149,16 +149,21 @@ debugging your compressed JavaScript.  To get a source map, pass
 `--source-map --output output.js` (source map will be written out to
 `output.js.map`).
 
-Additionally you might need `--source-map root=<URL>` to pass the URL where
-the original files can be found.  Use `--source-map url=<URL>` to specify
-the URL where the source map can be found.
+Additional options:
+
+- `--source-map filename=<NAME>` to specify the name of the source map.
+
+- `--source-map root=<URL>` to pass the URL where the original files can be found.
+  Otherwise UglifyJS assumes HTTP `X-SourceMap` is being used and will omit the
+  `//# sourceMappingURL=` directive.
+
+- `--source-map url=<URL>` to specify the URL where the source map can be found.
 
 For example:
 
-    uglifyjs /home/doe/work/foo/src/js/file1.js \
-             /home/doe/work/foo/src/js/file2.js \
+    uglifyjs js/file1.js js/file2.js \
              -o foo.min.js -c -m \
-             --source-map base="/home/doe/work/foo/src",root="http://foo.com/src"
+             --source-map root="http://foo.com/src",url=foo.min.js.map
 
 The above will compress and mangle `file1.js` and `file2.js`, will drop the
 output in `foo.min.js` and the source map in `foo.min.js.map`.  The source
@@ -177,11 +182,9 @@ CoffeeScript → compiled JS, UglifyJS can generate a map from CoffeeScript →
 compressed JS by mapping every token in the compiled JS to its original
 location.
 
-To use this feature you need to pass `--in-source-map
-/path/to/input/source.map` or `--in-source-map inline` if the source map is
-included inline with the sources. Normally the input source map should also
-point to the file containing the generated JS, so if that's correct you can
-omit input files from the command line.
+To use this feature pass `--source-map content="/path/to/input/source.map"`
+or `--source-map content=inline` if the source map is included inline with
+the sources.
 
 ## Mangler options
 
@@ -464,7 +467,7 @@ You can also use conditional compilation via the programmatic API. With the diff
 property name is `global_defs` and is a compressor property:
 
 ```js
-uglifyJS.minify([ "input.js"], {
+uglifyJS.minify(fs.readFileSync("input.js", "utf8"), {
     compress: {
         dead_code: true,
         global_defs: {
@@ -670,44 +673,47 @@ Other options:
 
 ##### mangle
 
- - `reserved` - pass an array of identifiers that should be excluded from mangling
+- `reserved` - pass an array of identifiers that should be excluded from mangling
 
- - `toplevel` — mangle names declared in the toplevel scope (disabled by
-  default).
+- `toplevel` — mangle names declared in the toplevel scope (disabled by
+default).
 
- - `eval` — mangle names visible in scopes where eval or with are used
-  (disabled by default).
+- `eval` — mangle names visible in scopes where eval or with are used
+(disabled by default).
 
- - `keep_fnames` -- default `false`.  Pass `true` to not mangle
-  function names.  Useful for code relying on `Function.prototype.name`.
-  See also: the `keep_fnames` [compress option](#compressor-options).
+- `keep_fnames` -- default `false`.  Pass `true` to not mangle
+function names.  Useful for code relying on `Function.prototype.name`.
+See also: the `keep_fnames` [compress option](#compressor-options).
 
-  Examples:
+Examples:
 
-  ```javascript
-  //tst.js
-  var globalVar;
-  function funcName(firstLongName, anotherLongName)
-  {
+```javascript
+// test.js
+var globalVar;
+function funcName(firstLongName, anotherLongName)
+{
     var myVariable = firstLongName +  anotherLongName;
-  }
+}
+```
+```javascript
+var code = fs.readFileSync("test.js", "utf8");
 
-  UglifyJS.minify("tst.js").code;
-  // 'function funcName(a,n){}var globalVar;'
+UglifyJS.minify(code).code;
+// 'function funcName(a,n){}var globalVar;'
 
-  UglifyJS.minify("tst.js", { mangle: { reserved: ['firstLongName'] } }).code;
-  // 'function funcName(firstLongName,a){}var globalVar;'
+UglifyJS.minify(code, { mangle: { reserved: ['firstLongName'] } }).code;
+// 'function funcName(firstLongName,a){}var globalVar;'
 
-  UglifyJS.minify("tst.js", { mangle: { toplevel: true } }).code;
-  // 'function n(n,a){}var a;'
-  ```
+UglifyJS.minify(code, { mangle: { toplevel: true } }).code;
+// 'function n(n,a){}var a;'
+```
 
 ##### mangle.properties options
 
- - `regex` — Pass a RegExp to only mangle certain names
- - `keep_quoted` — Only mangle unquoted property names
- - `debug` — Mangle names with the original name still present. Defaults to `false`.
-   Pass an empty string to enable, or a non-empty string to set the suffix.
+- `regex` — Pass a RegExp to only mangle certain names
+- `keep_quoted` — Only mangle unquoted property names
+- `debug` — Mangle names with the original name still present. Defaults to `false`.
+  Pass an empty string to enable, or a non-empty string to set the suffix.
 
-  [acorn]: https://github.com/ternjs/acorn
-  [sm-spec]: https://docs.google.com/document/d/1U1RGAehQwRypUTovF1KRlpiOFze0b-_2gc6fAH0KY0k
+[acorn]: https://github.com/ternjs/acorn
+[sm-spec]: https://docs.google.com/document/d/1U1RGAehQwRypUTovF1KRlpiOFze0b-_2gc6fAH0KY0k

lib/compress.js

@@ -525,6 +525,14 @@ merge(Compressor.prototype, {
         return lhs instanceof AST_SymbolRef && lhs.definition().orig[0] instanceof AST_SymbolLambda;
     }
 
+    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++)) {
@@ -790,7 +798,8 @@ merge(Compressor.prototype, {
                         return make_node(AST_SymbolRef, expr.name, expr.name);
                     }
                 } else {
-                    return expr[expr instanceof AST_Assign ? "left" : "expression"];
+                    var lhs = expr[expr instanceof AST_Assign ? "left" : "expression"];
+                    return !is_reference_const(lhs) && lhs;
                 }
             }
 
@@ -1973,6 +1982,7 @@ 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;
@@ -3178,7 +3188,7 @@ merge(Compressor.prototype, {
                     && (left.operator == "++" || left.operator == "--")) {
                     left = left.expression;
                 } else left = null;
-                if (!left || is_lhs_read_only(left)) {
+                if (!left || is_lhs_read_only(left) || is_reference_const(left)) {
                     expressions[++i] = cdr;
                     continue;
                 }

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": "3.0.3",
+  "version": "3.0.4",
   "engines": {
     "node": ">=0.8.0"
   },

test/compress/collapse_vars.js

@@ -2186,3 +2186,49 @@ compound_assignment: {
     }
     expect_stdout: "4"
 }
+
+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

@@ -1147,3 +1147,28 @@ var_catch_toplevel: {
         }();
     }
 }
+
+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/sequences.js

@@ -710,3 +710,27 @@ issue_27: {
         })(jQuery);
     }
 }
+
+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
+}