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fix corner case in string concatenations (#3692)

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- migrate de-facto compression to `conditionals` & `strings`

fixes #3689
This commit is contained in:
Alex Lam S.L
2020-01-28 07:33:11 +08:00
committed by GitHub
parent 0dcedad2d5
commit e9e76dcf04
6 changed files with 164 additions and 98 deletions
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54
lib/compress.js
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@@ -83,6 +83,7 @@ function Compressor(options, false_by_default) {
reduce_vars : !false_by_default,
sequences : !false_by_default,
side_effects : !false_by_default,
strings : !false_by_default,
switches : !false_by_default,
top_retain : null,
toplevel : !!(options && options["top_retain"]),
@@ -6188,6 +6189,18 @@ merge(Compressor.prototype, {
self.right = tmp;
}
}
function swap_chain() {
var rhs = self.right;
self.left = make_node(AST_Binary, self, {
operator: self.operator,
left: self.left,
right: rhs.left,
start: self.left.start,
end: rhs.left.end
});
self.right = rhs.right;
self.left = self.left.transform(compressor);
}
if (commutativeOperators[self.operator]
&& self.right.is_constant()
&& !self.left.is_constant()
@@ -6338,17 +6351,28 @@ merge(Compressor.prototype, {
case ">=": reverse("<="); break;
}
}
if (self.operator == "+") {
// x && (y && z) => x && y && z
// x || (y || z) => x || y || z
if (compressor.option("conditionals")
&& lazy_op[self.operator]
&& self.right instanceof AST_Binary
&& self.operator == self.right.operator) {
swap_chain();
}
if (compressor.option("strings") && self.operator == "+") {
// "foo" + 42 + "" => "foo" + 42
if (self.right instanceof AST_String
&& self.right.value == ""
&& self.left.is_string(compressor)) {
return self.left.optimize(compressor);
}
// "" + ("foo" + 42) => "foo" + 42
if (self.left instanceof AST_String
&& self.left.value == ""
&& self.right.is_string(compressor)) {
return self.right.optimize(compressor);
}
// "" + 42 + "foo" => 42 + "foo"
if (self.left instanceof AST_Binary
&& self.left.operator == "+"
&& self.left.left instanceof AST_String
@@ -6357,6 +6381,14 @@ merge(Compressor.prototype, {
self.left = self.left.right;
return self.optimize(compressor);
}
// "x" + (y + "z") => "x" + y + "z"
// x + ("y" + z) => x + "y" + z
if (self.right instanceof AST_Binary
&& self.operator == self.right.operator
&& (self.left.is_string(compressor) && self.right.is_string(compressor)
|| self.right.left.is_string(compressor) && !self.right.right.has_side_effects(compressor))) {
swap_chain();
}
}
if (compressor.option("evaluate")) {
var associative = true;
@@ -6727,26 +6759,6 @@ merge(Compressor.prototype, {
return node.optimize(compressor);
}
}
// x && (y && z) => x && y && z
// x || (y || z) => x || y || z
// x + ("y" + z) => x + "y" + z
// "x" + (y + "z") => "x" + y + "z"
if (self.right instanceof AST_Binary
&& self.right.operator == self.operator
&& (lazy_op[self.operator]
|| (self.operator == "+"
&& (self.right.left.is_string(compressor)
|| (self.left.is_string(compressor)
&& self.right.right.is_string(compressor))))))
{
self.left = make_node(AST_Binary, self.left, {
operator : self.operator,
left : self.left,
right : self.right.left
});
self.right = self.right.right;
return self.transform(compressor);
}
return try_evaluate(compressor, self);
function align(ref, op) {