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enhance awaits (#4969)

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This commit is contained in:
Alex Lam S.L
2021-05-27 17:57:14 +01:00
committed by GitHub
parent 362abe0ffb
commit ab42a90edb
2 changed files with 61 additions and 22 deletions
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77
lib/compress.js
View File

@@ -309,18 +309,14 @@ merge(Compressor.prototype, {
var self = this;
var tt = new TreeTransformer(function(node) {
if (insert && node instanceof AST_SimpleStatement) {
return make_node(AST_Return, node, {
value: node.body
});
return transform ? transform(node) : make_node(AST_Return, node, { value: node.body });
}
if (!insert && node instanceof AST_Return) {
return transform ? transform(node) : make_node(AST_SimpleStatement, node, {
body: node.value || make_node(AST_UnaryPrefix, node, {
operator: "void",
expression: make_node(AST_Number, node, {
value: 0
})
})
expression: make_node(AST_Number, node, { value: 0 }),
}),
});
}
if (node instanceof AST_Lambda && node !== self) {
@@ -7533,8 +7529,43 @@ merge(Compressor.prototype, {
node.value = value.drop_side_effect_free(compressor);
}
});
if (async && compressor.option("awaits")) {
exp.process_expression(true, function(node) {
var body = node.body;
if (body instanceof AST_Await) {
if (is_primitive(compressor, body.expression)) {
body = body.expression.drop_side_effect_free(compressor, true);
if (!body) return make_node(AST_EmptyStatement, node);
node.body = body;
}
} else if (body instanceof AST_Sequence) {
var tail = body.tail_node();
if (tail instanceof AST_Await && is_primitive(compressor, tail.expression)) {
tail = tail.expression.drop_side_effect_free(compressor);
body.expressions.pop();
if (tail) body.expressions.push(tail);
}
}
return node;
});
if (all(exp.body, is_empty) && !(is_arrow(exp) && exp.value)) {
var ctor;
switch (exp.CTOR) {
case AST_AsyncArrow:
ctor = AST_Arrow;
break;
case AST_AsyncFunction:
ctor = AST_Function;
break;
case AST_AsyncGeneratorFunction:
ctor = AST_GeneratorFunction;
break;
}
return make_node(ctor, exp, exp);
}
}
return exp.clone();
}
return drop_body;
}
def(AST_Call, function(compressor, first_in_statement) {
var self = this;
@@ -7557,10 +7588,11 @@ merge(Compressor.prototype, {
var opt = call.transform(compressor);
if (opt !== call) return opt.drop_side_effect_free(compressor, first_in_statement);
}
if (drop_returns(compressor, exp)) {
var dropped = drop_returns(compressor, exp);
if (dropped) {
// always shallow clone to ensure stripping of negated IIFEs
self = self.clone();
self.expression = exp.clone();
self.expression = dropped;
// avoid extraneous traversal
if (exp._squeezed) self.expression._squeezed = true;
}
@@ -7759,10 +7791,11 @@ merge(Compressor.prototype, {
return make_sequence(self, expressions).drop_side_effect_free(compressor, first_in_statement);
}
var tag = self.tag;
if (drop_returns(compressor, tag)) {
var dropped = drop_returns(compressor, tag);
if (dropped) {
// always shallow clone to signal internal changes
self = self.clone();
self.tag = tag.clone();
self.tag = dropped;
// avoid extraneous traversal
if (tag._squeezed) self.tag._squeezed = true;
}
@@ -9817,15 +9850,23 @@ merge(Compressor.prototype, {
}
if (compressor.option("side_effects")) {
var exp = self.expression;
if (exp instanceof AST_Await) return exp;
if (exp instanceof AST_Await) return exp.optimize(compressor);
if (exp instanceof AST_UnaryPrefix) {
if (exp.expression instanceof AST_Await) return exp;
if (exp.expression instanceof AST_Await) return exp.optimize(compressor);
if (exp.operator == "void") return make_node(AST_UnaryPrefix, self, {
operator: "void",
expression: make_node(AST_Await, self, {
expression: exp.expression,
}),
});
expression: make_node(AST_Await, self, { expression: exp.expression }),
}).optimize(compressor);
}
for (var level = 0, node = self, parent; parent = compressor.parent(level++); node = parent) {
if (is_arrow(parent)) {
if (parent.value === node) return exp.optimize(compressor);
} else if (parent instanceof AST_Return) {
return exp.optimize(compressor);
} else if (parent instanceof AST_Sequence) {
if (parent.tail_node() === node) continue;
}
break;
}
}
return self;

6
test/compress/awaits.js
View File

@@ -227,9 +227,7 @@ inline_await_1_trim: {
console.log("PASS");
}
expect: {
(async function() {
await 0;
})();
void 0;
console.log("PASS");
}
expect_stdout: "PASS"
@@ -334,7 +332,7 @@ inline_await_3_trim: {
}
expect: {
(async function() {
return a = "PASS", b = console.log, await b(a);
return a = "PASS", b = console.log, b(a);
var a, b;
})();
}