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Keep unused function arguments by default

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Discarding unused function arguments affects function.length, which can lead
to some hard to debug issues.  This optimization is now done only in "unsafe
mode".

Fix #121
This commit is contained in:
Mihai Bazon
2015-03-20 10:28:51 +02:00
parent d36faffeca
commit ecfd881ac6
3 changed files with 8 additions and 7 deletions
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5
README.md
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@@ -272,14 +272,15 @@ contrived cases, but should be fine for most code. You might want to try it
on your own code, it should reduce the minified size. Here's what happens on your own code, it should reduce the minified size. Here's what happens
when this flag is on: when this flag is on:
- `new Array(1, 2, 3)` or `Array(1, 2, 3)` → `[1, 2, 3 ]` - `new Array(1, 2, 3)` or `Array(1, 2, 3)` → `[ 1, 2, 3 ]`
- `new Object()` → `{}` - `new Object()` → `{}`
- `String(exp)` or `exp.toString()` → `"" + exp` - `String(exp)` or `exp.toString()` → `"" + exp`
- `new Object/RegExp/Function/Error/Array (...)` → we discard the `new` - `new Object/RegExp/Function/Error/Array (...)` → we discard the `new`
- `typeof foo == "undefined"` → `foo === void 0` - `typeof foo == "undefined"` → `foo === void 0`
- `void 0` → `undefined` (if there is a variable named "undefined" in - `void 0` → `undefined` (if there is a variable named "undefined" in
scope; we do it because the variable name will be mangled, typically scope; we do it because the variable name will be mangled, typically
reduced to a single character). reduced to a single character)
- discards unused function arguments (affects `function.length`)
### Conditional compilation ### Conditional compilation

2
lib/compress.js
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@@ -1086,7 +1086,7 @@ merge(Compressor.prototype, {
var tt = new TreeTransformer( var tt = new TreeTransformer(
function before(node, descend, in_list) { function before(node, descend, in_list) {
if (node instanceof AST_Lambda && !(node instanceof AST_Accessor)) { if (node instanceof AST_Lambda && !(node instanceof AST_Accessor)) {
if (!compressor.option("keep_fargs")) { if (compressor.option("unsafe") && !compressor.option("keep_fargs")) {
for (var a = node.argnames, i = a.length; --i >= 0;) { for (var a = node.argnames, i = a.length; --i >= 0;) {
var sym = a[i]; var sym = a[i];
if (sym.unreferenced()) { if (sym.unreferenced()) {

6
test/compress/drop-unused.js
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@@ -1,5 +1,5 @@
unused_funarg_1: { unused_funarg_1: {
options = { unused: true }; options = { unused: true, unsafe: true };
input: { input: {
function f(a, b, c, d, e) { function f(a, b, c, d, e) {
return a + b; return a + b;
@@ -13,7 +13,7 @@ unused_funarg_1: {
} }
unused_funarg_2: { unused_funarg_2: {
options = { unused: true }; options = { unused: true, unsafe: true };
input: { input: {
function f(a, b, c, d, e) { function f(a, b, c, d, e) {
return a + c; return a + c;
@@ -165,7 +165,7 @@ used_var_in_catch: {
} }
keep_fnames: { keep_fnames: {
options = { unused: true, keep_fnames: true }; options = { unused: true, keep_fnames: true, unsafe: true };
input: { input: {
function foo() { function foo() {
return function bar(baz) {}; return function bar(baz) {};