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enhance assignments, booleans & conditionals (#5691)
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@alexlamsl
alexlamsl authored Oct 3, 2022
1 parent 6cdc035 commit 80fc862
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Showing 6 changed files with 164 additions and 58 deletions.
94 changes: 56 additions & 38 deletions lib/compress.js
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Original file line number Diff line number Diff line change
Expand Up @@ -11589,12 +11589,18 @@ Compressor.prototype.compress = function(node) {
if (node instanceof AST_Unary) return true;
}

function extract_lhs(node) {
if (node instanceof AST_Assign) return node.left;
if (node instanceof AST_Sequence) return extract_lhs(node.tail_node());
if (node instanceof AST_UnaryPrefix && UNARY_POSTFIX[node.operator]) return node.expression;
return node;
}

function repeatable(compressor, node) {
if (node instanceof AST_Dot) return repeatable(compressor, node.expression);
if (node instanceof AST_Sub) {
return repeatable(compressor, node.expression) && repeatable(compressor, node.property);
}
if (node instanceof AST_Symbol) return true;
return !node.has_side_effects(compressor);
}

Expand Down Expand Up @@ -11631,31 +11637,32 @@ Compressor.prototype.compress = function(node) {
if (seq !== self) return seq.optimize(compressor);
}
if (compressor.option("assignments") && lazy_op[self.operator]) {
var lhs = extract_lhs(self.left);
var right = self.right;
// a || (a = x) ---> a = a || x
// a && (a = x) ---> a = a && x
if (self.left instanceof AST_SymbolRef
// (a = x) && (a = y) ---> a = (a = x) && y
if (lhs instanceof AST_SymbolRef
&& right instanceof AST_Assign
&& right.operator == "="
&& self.left.equals(right.left)) {
var left = right.left.clone();
&& lhs.equals(right.left)) {
lhs = lhs.clone();
var assign = make_node(AST_Assign, self, {
operator: "=",
left: left,
left: lhs,
right: make_node(AST_Binary, self, {
operator: self.operator,
left: self.left,
right: right.right,
}),
});
if (left.fixed) {
left.fixed = function() {
if (lhs.fixed) {
lhs.fixed = function() {
return assign.right;
};
left.fixed.assigns = [ assign ];
lhs.fixed.assigns = [ assign ];
}
var def = left.definition();
def.references.push(left);
var def = lhs.definition();
def.references.push(lhs);
def.replaced++;
return assign.optimize(compressor);
}
Expand Down Expand Up @@ -11710,31 +11717,32 @@ Compressor.prototype.compress = function(node) {
case "||":
// void 0 !== x && null !== x ---> null != x
// void 0 === x || null === x ---> null == x
var lhs = self.left;
if (lhs.operator == self.operator) lhs = lhs.right;
var expr = lhs.right;
if (expr instanceof AST_Assign && expr.operator == "=") expr = expr.left;
if (lhs instanceof AST_Binary
&& lhs.operator == (self.operator == "&&" ? "!==" : "===")
&& self.right instanceof AST_Binary
&& lhs.operator == self.right.operator
&& (is_undefined(lhs.left, compressor) && self.right.left instanceof AST_Null
|| lhs.left instanceof AST_Null && is_undefined(self.right.left, compressor))
&& !expr.has_side_effects(compressor)
&& expr.equals(self.right.right)) {
lhs.operator = lhs.operator.slice(0, -1);
lhs.left = make_node(AST_Null, self);
return self.left;
var left = self.left;
if (!(left instanceof AST_Binary)) break;
if (left.operator != (self.operator == "&&" ? "!==" : "===")) break;
if (!(self.right instanceof AST_Binary)) break;
if (left.operator != self.right.operator) break;
if (is_undefined(left.left, compressor) && self.right.left instanceof AST_Null
|| left.left instanceof AST_Null && is_undefined(self.right.left, compressor)) {
var expr = left.right;
if (expr instanceof AST_Assign && expr.operator == "=") expr = expr.left;
if (expr.has_side_effects(compressor)) break;
if (!expr.equals(self.right.right)) break;
left.operator = left.operator.slice(0, -1);
left.left = make_node(AST_Null, self);
return left;
}
break;
}
var in_bool = false;
var parent = compressor.parent();
if (compressor.option("booleans")) {
var lhs = self.left;
var lhs = extract_lhs(self.left);
if (lazy_op[self.operator] && !lhs.has_side_effects(compressor)) {
// a || a ---> a
// (a = x) && a --> a = x
if (lhs.equals(self.right)) {
return maintain_this_binding(parent, compressor.self(), lhs).optimize(compressor);
return maintain_this_binding(parent, compressor.self(), self.left).optimize(compressor);
}
mark_duplicate_condition(compressor, lhs);
}
Expand Down Expand Up @@ -11782,13 +11790,22 @@ Compressor.prototype.compress = function(node) {
case ">=": reverse("<="); break;
}
}
// 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(self, compressor);
if (compressor.option("conditionals") && lazy_op[self.operator]) {
if (self.left instanceof AST_Binary && self.operator == self.left.operator) {
var before = make_node(AST_Binary, self, {
operator: self.operator,
left: self.left.right,
right: self.right,
});
var after = before.optimize(compressor);
if (before !== after) {
self.left = self.left.left;
self.right = after;
}
}
// x && (y && z) ---> x && y && z
// x || (y || z) ---> x || y || z
if (self.right instanceof AST_Binary && self.operator == self.right.operator) swap_chain(self, compressor);
}
if (compressor.option("strings") && self.operator == "+") {
// "foo" + 42 + "" ---> "foo" + 42
Expand Down Expand Up @@ -12881,15 +12898,16 @@ Compressor.prototype.compress = function(node) {
}
var consequent = self.consequent;
var alternative = self.alternative;
if (repeatable(compressor, condition)) {
var cond_lhs = extract_lhs(condition);
if (repeatable(compressor, cond_lhs)) {
// x ? x : y ---> x || y
if (condition.equals(consequent)) return make_node(AST_Binary, self, {
if (cond_lhs.equals(consequent)) return make_node(AST_Binary, self, {
operator: "||",
left: condition,
right: alternative,
}).optimize(compressor);
// x ? y : x ---> x && y
if (condition.equals(alternative)) return make_node(AST_Binary, self, {
if (cond_lhs.equals(alternative)) return make_node(AST_Binary, self, {
operator: "&&",
left: condition,
right: consequent,
Expand Down
39 changes: 39 additions & 0 deletions test/compress/assignments.js
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Original file line number Diff line number Diff line change
Expand Up @@ -290,6 +290,45 @@ increment_decrement_2: {
expect_stdout: "42"
}

lazily_chained_assignments: {
options = {
assignments: true,
collapse_vars: true,
conditionals: true,
unused: true,
}
input: {
function f(a) {
if (a = console.log("foo"))
a = console.log("bar");
return a;
}
function g(b) {
if (b = console.log("baz"))
;
else
b = console.log("moo");
return b;
}
console.log(f(), g());
}
expect: {
function f(a) {
return console.log("foo") && console.log("bar");
}
function g(b) {
return console.log("baz") || console.log("moo");
}
console.log(f(), g());
}
expect_stdout: [
"foo",
"baz",
"moo",
"undefined undefined",
]
}

issue_3375_1: {
options = {
assignments: true,
Expand Down
44 changes: 44 additions & 0 deletions test/compress/booleans.js
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Original file line number Diff line number Diff line change
Expand Up @@ -80,6 +80,25 @@ de_morgan_1c: {
expect_stdout: "true"
}

de_morgan_1d: {
options = {
booleans: true,
}
input: {
function f(a) {
return (a = false) || a;
}
console.log(f(null), f(42));
}
expect: {
function f(a) {
return a = !1;
}
console.log(f(null), f(42));
}
expect_stdout: "false false"
}

de_morgan_2a: {
options = {
booleans: true,
Expand Down Expand Up @@ -181,6 +200,31 @@ de_morgan_2d: {
]
}

de_morgan_2e: {
options = {
booleans: true,
conditionals: true,
}
input: {
function f(a, b) {
return (a && b) && b;
}
console.log(f(null), f(null, {}));
console.log(f(42), f(42, {}));
}
expect: {
function f(a, b) {
return a && b;
}
console.log(f(null), f(null, {}));
console.log(f(42), f(42, {}));
}
expect_stdout: [
"null null",
"undefined {}",
]
}

de_morgan_3a: {
options = {
booleans: true,
Expand Down
5 changes: 5 additions & 0 deletions test/compress/comparisons.js
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Original file line number Diff line number Diff line change
Expand Up @@ -76,12 +76,14 @@ self_comparison_1: {
comparisons: true,
}
input: {
var a, b;
a === a;
a !== b;
b.c === a.c;
b.c !== b.c;
}
expect: {
var a, b;
a == a;
a !== b;
b.c === a.c;
Expand Down Expand Up @@ -275,6 +277,7 @@ issue_2857_3: {
issue_2857_4: {
options = {
comparisons: true,
conditionals: true,
}
input: {
function f(a, p) {
Expand Down Expand Up @@ -305,6 +308,7 @@ issue_2857_4: {
issue_2857_5: {
options = {
comparisons: true,
conditionals: true,
}
input: {
function f(a, p) {
Expand Down Expand Up @@ -528,6 +532,7 @@ nullish_assign: {
nullish_chain: {
options = {
comparisons: true,
conditionals: true,
}
input: {
var a;
Expand Down
2 changes: 1 addition & 1 deletion test/compress/conditionals.js
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Original file line number Diff line number Diff line change
Expand Up @@ -3028,7 +3028,7 @@ issue_5673_2: {
expect: {
var a = "PASS";
console.log(function(b) {
return ((b = a) || (b = a)) && b;
return a || (b = a) && b;
}());
}
expect_stdout: "PASS"
Expand Down
38 changes: 19 additions & 19 deletions test/compress/if_return.js
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Original file line number Diff line number Diff line change
Expand Up @@ -976,33 +976,33 @@ nested_if_return: {
if_return: true,
}
input: {
function f() {
if (A) {
if (B)
return B;
if (C)
return D;
if (E)
return F;
if (G)
return H;
if (I) {
if (J)
return K;
function f(a, b, c, d, e, f, g, h, i, j, k, l, m, n) {
if (a) {
if (b)
return b;
if (c)
return d;
if (e)
return f;
if (g)
return h;
if (i) {
if (j)
return k;
return;
}
if (L) {
if (M)
if (l) {
if (m)
return;
return N;
return n;
}
}
}
}
expect: {
function f() {
if (A)
return B || (C ? D : E ? F : G ? H : I ? J ? K : void 0 : L && !M ? N : void 0);
function f(a, b, c, d, e, f, g, h, i, j, k, l, m, n) {
if (a)
return b || (c ? d : e ? f : g ? h : i ? j ? k : void 0 : l && !m ? n : void 0);
}
}
}
Expand Down

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