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transform String.charAt() to index access (#1620)

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Guarded by `unsafe` as `charAt()` can be overridden.
This commit is contained in:
Alex Lam S.L
2017-03-19 02:17:15 +08:00
committed by GitHub
parent 0489d6de64
commit 274331d0ea
2 changed files with 94 additions and 6 deletions
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22
lib/compress.js
View File

@@ -2656,7 +2656,7 @@ merge(Compressor.prototype, {
if (self.args.length != 1) {
return make_node(AST_Array, self, {
elements: self.args
}).transform(compressor);
}).optimize(compressor);
}
break;
case "Object":
@@ -2674,7 +2674,7 @@ merge(Compressor.prototype, {
left: self.args[0],
operator: "+",
right: make_node(AST_String, self, { value: "" })
}).transform(compressor);
}).optimize(compressor);
break;
case "Number":
if (self.args.length == 0) return make_node(AST_Number, self, {
@@ -2683,7 +2683,7 @@ merge(Compressor.prototype, {
if (self.args.length == 1) return make_node(AST_UnaryPrefix, self, {
expression: self.args[0],
operator: "+"
}).transform(compressor);
}).optimize(compressor);
case "Boolean":
if (self.args.length == 0) return make_node(AST_False, self);
if (self.args.length == 1) return make_node(AST_UnaryPrefix, self, {
@@ -2692,7 +2692,7 @@ merge(Compressor.prototype, {
operator: "!"
}),
operator: "!"
}).transform(compressor);
}).optimize(compressor);
break;
case "Function":
// new Function() => function(){}
@@ -2757,7 +2757,7 @@ merge(Compressor.prototype, {
left: make_node(AST_String, self, { value: "" }),
operator: "+",
right: exp.expression
}).transform(compressor);
}).optimize(compressor);
}
else if (exp instanceof AST_Dot && exp.expression instanceof AST_Array && exp.property == "join") EXIT: {
var separator;
@@ -2811,7 +2811,7 @@ merge(Compressor.prototype, {
left : prev,
right : el
});
}, first).transform(compressor);
}, first).optimize(compressor);
}
// need this awkward cloning to not affect original element
// best_of will decide which one to get through.
@@ -2821,6 +2821,16 @@ merge(Compressor.prototype, {
node.expression.expression.elements = elements;
return best_of(compressor, self, node);
}
else if (exp instanceof AST_Dot && exp.expression.is_string(compressor) && exp.property == "charAt") {
var arg = self.args[0];
var index = arg ? arg.evaluate(compressor) : 0;
if (index !== arg) {
return make_node(AST_Sub, exp, {
expression: exp.expression,
property: make_node_from_constant(index | 0, arg || exp)
}).optimize(compressor);
}
}
}
if (exp instanceof AST_Function) {
if (exp.body[0] instanceof AST_Return) {

78
test/compress/evaluate.js
View File

@@ -200,6 +200,7 @@ negative_zero: {
1 / (-0)
);
}
expect_stdout: true
}
positive_zero: {
@@ -220,6 +221,7 @@ positive_zero: {
1 / (0)
);
}
expect_stdout: true
}
unsafe_constant: {
@@ -411,6 +413,7 @@ unsafe_integer_key: {
1["1"] + 1
);
}
expect_stdout: true
}
unsafe_integer_key_complex: {
@@ -438,6 +441,7 @@ unsafe_integer_key_complex: {
2
);
}
expect_stdout: true
}
unsafe_float_key: {
@@ -465,6 +469,7 @@ unsafe_float_key: {
1["3.14"] + 1
);
}
expect_stdout: true
}
unsafe_float_key_complex: {
@@ -492,6 +497,7 @@ unsafe_float_key_complex: {
2
);
}
expect_stdout: true
}
unsafe_array: {
@@ -554,6 +560,7 @@ unsafe_string: {
"11"
);
}
expect_stdout: true
}
unsafe_array_bad_index: {
@@ -575,6 +582,7 @@ unsafe_array_bad_index: {
[1, 2, 3, 4][3.14] + 1
);
}
expect_stdout: true
}
unsafe_string_bad_index: {
@@ -596,6 +604,7 @@ unsafe_string_bad_index: {
"1234"[3.14] + 1
);
}
expect_stdout: true
}
unsafe_prototype_function: {
@@ -701,3 +710,72 @@ in_boolean_context: {
);
}
}
unsafe_charAt: {
options = {
evaluate : true,
unsafe : true
}
input: {
console.log(
"1234" + 1,
"1234".charAt(0) + 1,
"1234".charAt(6 - 5) + 1,
("12" + "34").charAt(0) + 1,
("12" + "34").charAt(6 - 5) + 1,
[1, 2, 3, 4].join("").charAt(0) + 1
);
}
expect: {
console.log(
"12341",
"11",
"21",
"11",
"21",
"11"
);
}
expect_stdout: true
}
unsafe_charAt_bad_index: {
options = {
evaluate : true,
unsafe : true
}
input: {
console.log(
"1234".charAt() + 1,
"1234".charAt("a") + 1,
"1234".charAt(3.14) + 1
);
}
expect: {
console.log(
"11",
"11",
"41"
);
}
expect_stdout: true
}
unsafe_charAt_noop: {
options = {
evaluate : true,
unsafe : true
}
input: {
console.log(
s.charAt(0),
"string".charAt(x)
);
}
expect: {
console.log(
s.charAt(0),
"string".charAt(x)
);
}
}