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introduce "strict" to pure_getters (#1795)
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alexlamsl authored Apr 7, 2017
1 parent 281e882 commit 0f4cd73
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Showing 4 changed files with 59 additions and 16 deletions.
2 changes: 2 additions & 0 deletions README.md
Original file line number Diff line number Diff line change
Expand Up @@ -411,6 +411,8 @@ to set `true`; it's effectively a shortcut for `foo=true`).
- `pure_getters` -- the default is `false`. If you pass `true` for
this, UglifyJS will assume that object property access
(e.g. `foo.bar` or `foo["bar"]`) doesn't have any side effects.
Specify `"strict"` to treat `foo.bar` as side-effect-free only when
`foo` is certain to not throw, i.e. not `null` or `undefined`.

- `pure_funcs` -- default `null`. You can pass an array of names and
UglifyJS will assume that those functions do not produce side
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15 changes: 9 additions & 6 deletions lib/compress.js
Original file line number Diff line number Diff line change
Expand Up @@ -71,7 +71,7 @@ function Compressor(options, false_by_default) {
negate_iife : !false_by_default,
passes : 1,
properties : !false_by_default,
pure_getters : false,
pure_getters : !false_by_default && "strict",
pure_funcs : null,
reduce_vars : !false_by_default,
screw_ie8 : true,
Expand Down Expand Up @@ -1165,7 +1165,13 @@ merge(Compressor.prototype, {
// may_eq_null()
// returns true if this node may evaluate to null or undefined
(function(def) {
def(AST_Node, return_true);
function is_strict(compressor) {
return /strict/.test(compressor.option("pure_getters"));
}

def(AST_Node, function(compressor) {
return !is_strict(compressor);
});
def(AST_Null, return_true);
def(AST_Undefined, return_true);
def(AST_Constant, return_false);
Expand Down Expand Up @@ -1198,12 +1204,9 @@ merge(Compressor.prototype, {
def(AST_Seq, function(compressor) {
return this.cdr.may_eq_null(compressor);
});
def(AST_PropAccess, function(compressor) {
return !compressor.option("unsafe");
});
def(AST_SymbolRef, function(compressor) {
if (this.is_undefined) return true;
if (compressor.option("unsafe")) return false;
if (!is_strict(compressor)) return false;
var fixed = this.fixed_value();
return !fixed || fixed.may_eq_null(compressor);
});
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39 changes: 31 additions & 8 deletions test/compress/pure_getters.js
Original file line number Diff line number Diff line change
@@ -1,10 +1,9 @@
side_effects: {
strict: {
options = {
pure_getters: true,
pure_getters: "strict",
reduce_vars: false,
side_effects: true,
toplevel: true,
unsafe: false,
}
input: {
var a, b = null, c = {};
Expand All @@ -28,13 +27,12 @@ side_effects: {
}
}

side_effects_reduce_vars: {
strict_reduce_vars: {
options = {
pure_getters: true,
pure_getters: "strict",
reduce_vars: true,
side_effects: true,
toplevel: true,
unsafe: false,
}
input: {
var a, b = null, c = {};
Expand All @@ -57,13 +55,38 @@ side_effects_reduce_vars: {
}
}

side_effects_unsafe: {
unsafe: {
options = {
pure_getters: true,
reduce_vars: false,
side_effects: true,
toplevel: true,
unsafe: true,
}
input: {
var a, b = null, c = {};
a.prop;
b.prop;
c.prop;
d.prop;
null.prop;
(void 0).prop;
undefined.prop;
}
expect: {
var a, b = null, c = {};
d;
null.prop;
(void 0).prop;
(void 0).prop;
}
}

unsafe_reduce_vars: {
options = {
pure_getters: true,
reduce_vars: true,
side_effects: true,
toplevel: true,
}
input: {
var a, b = null, c = {};
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19 changes: 17 additions & 2 deletions test/compress/reduce_vars.js
Original file line number Diff line number Diff line change
Expand Up @@ -1919,7 +1919,7 @@ side_effects_assign: {

pure_getters_1: {
options = {
pure_getters: true,
pure_getters: "strict",
reduce_vars: true,
side_effects: true,
toplevel: true,
Expand All @@ -1941,7 +1941,7 @@ pure_getters_1: {

pure_getters_2: {
options = {
pure_getters: true,
pure_getters: "strict",
reduce_vars: true,
toplevel: true,
unused: true,
Expand All @@ -1956,6 +1956,21 @@ pure_getters_2: {
}
}

pure_getters_3: {
options = {
pure_getters: true,
reduce_vars: true,
toplevel: true,
unused: true,
}
input: {
var a;
var a = a && a.b;
}
expect: {
}
}

catch_var: {
options = {
booleans: true,
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