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enhance booleans (#5022)

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closes #5021
This commit is contained in:
Alex Lam S.L
2021-06-22 17:35:50 +01:00
committed by GitHub
parent e9c902b044
commit 7c5b6f349e
7 changed files with 639 additions and 30 deletions
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107
lib/compress.js
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@@ -8223,35 +8223,86 @@ merge(Compressor.prototype, {
}
}
function fuzzy_eval(compressor, node, nullish) {
if (node.truthy) return true;
if (node.falsy && !nullish) return false;
if (node.is_truthy()) return true;
return node.evaluate(compressor, true);
}
function mark_duplicate_condition(compressor, node) {
for (var level = 0, child = compressor.self(), parent; ; child = parent) {
parent = compressor.parent(level++);
if (parent instanceof AST_Binary) {
var op = parent.operator;
if (!lazy_op[op]) return;
var left = parent.left;
if (left === child) continue;
if (node.equivalent_to(left)) node[op == "&&" ? "truthy" : "falsy"] = true;
} else if (parent instanceof AST_Conditional) {
var cond = parent.condition;
if (cond === child) continue;
if (node.equivalent_to(cond)) switch (child) {
case parent.consequent:
node.truthy = true;
break;
case parent.alternative:
node.falsy = true;
break;
}
} else if (parent instanceof AST_Exit) {
break;
} else if (parent instanceof AST_If) {
break;
} else if (parent instanceof AST_Sequence) {
if (parent.expressions[0] === child) continue;
} else if (parent instanceof AST_SimpleStatement) {
break;
}
return;
}
while (true) {
child = parent;
parent = compressor.parent(level++);
if (parent instanceof AST_BlockStatement) {
if (parent.body[0] === child) continue;
} else if (parent instanceof AST_If) {
var cond = parent.condition;
if (cond === child) continue;
if (node.equivalent_to(cond)) switch (child) {
case parent.body:
node.truthy = true;
break;
case parent.alternative:
node.falsy = true;
break;
}
}
return;
}
}
OPT(AST_If, function(self, compressor) {
if (is_empty(self.alternative)) self.alternative = null;
if (!compressor.option("conditionals")) return self;
if (compressor.option("booleans")) mark_duplicate_condition(compressor, self.condition);
// if condition can be statically determined, warn and drop
// one of the blocks. note, statically determined implies
// “has no side effects”; also it doesn't work for cases like
// `x && true`, though it probably should.
if (compressor.option("dead_code")) {
var cond = self.condition.evaluate(compressor);
if (cond instanceof AST_Node) {
cond = self.condition.is_truthy() || self.condition.evaluate(compressor, true);
}
var cond = fuzzy_eval(compressor, self.condition);
if (!cond) {
AST_Node.warn("Condition always false [{file}:{line},{col}]", self.condition.start);
var body = [
make_node(AST_SimpleStatement, self.condition, {
body: self.condition
}),
];
var body = [ make_node(AST_SimpleStatement, self.condition, { body: self.condition }) ];
extract_declarations_from_unreachable_code(compressor, self.body, body);
if (self.alternative) body.push(self.alternative);
return make_node(AST_BlockStatement, self, { body: body }).optimize(compressor);
} else if (!(cond instanceof AST_Node)) {
AST_Node.warn("Condition always true [{file}:{line},{col}]", self.condition.start);
var body = [
make_node(AST_SimpleStatement, self.condition, {
body: self.condition
}),
make_node(AST_SimpleStatement, self.condition, { body: self.condition }),
self.body,
];
if (self.alternative) extract_declarations_from_unreachable_code(compressor, self.alternative, body);
@@ -8275,9 +8326,7 @@ merge(Compressor.prototype, {
var body_exprs = sequencesize(self.body, body, var_defs, refs);
var alt_exprs = sequencesize(self.alternative, body, var_defs, refs);
if (body_exprs && alt_exprs) {
if (var_defs.length > 0) body.push(make_node(AST_Var, self, {
definitions: var_defs
}));
if (var_defs.length > 0) body.push(make_node(AST_Var, self, { definitions: var_defs }));
if (body_exprs.length == 0) {
body.push(make_node(AST_SimpleStatement, self.condition, {
body: alt_exprs.length > 0 ? make_node(AST_Binary, self, {
@@ -10221,7 +10270,18 @@ merge(Compressor.prototype, {
}
break;
}
var in_bool = compressor.option("booleans") && compressor.in_boolean_context();
var in_bool = false;
var parent = compressor.parent();
if (compressor.option("booleans")) {
var lhs = self.left;
if (lazy_op[self.operator] && !lhs.has_side_effects(compressor)) {
if (lhs.equivalent_to(self.right)) {
return maintain_this_binding(compressor, parent, compressor.self(), lhs).optimize(compressor);
}
mark_duplicate_condition(compressor, lhs);
}
in_bool = compressor.in_boolean_context();
}
if (in_bool) switch (self.operator) {
case "+":
var ll = self.left.evaluate(compressor);
@@ -10255,7 +10315,6 @@ merge(Compressor.prototype, {
}
break;
}
var parent = compressor.parent();
if (compressor.option("comparisons") && self.is_boolean(compressor)) {
if (!(parent instanceof AST_Binary) || parent instanceof AST_Assign) {
var negated = best_of(compressor, self, make_node(AST_UnaryPrefix, self, {
@@ -10313,7 +10372,7 @@ merge(Compressor.prototype, {
var associative = true;
switch (self.operator) {
case "&&":
var ll = fuzzy_eval(self.left);
var ll = fuzzy_eval(compressor, self.left);
if (!ll) {
AST_Node.warn("Condition left of && always false [{file}:{line},{col}]", self.start);
return maintain_this_binding(compressor, parent, compressor.self(), self.left).optimize(compressor);
@@ -10349,7 +10408,7 @@ merge(Compressor.prototype, {
case "??":
var nullish = true;
case "||":
var ll = fuzzy_eval(self.left, nullish);
var ll = fuzzy_eval(compressor, self.left, nullish);
if (nullish ? ll == null : !ll) {
AST_Node.warn("Condition left of {operator} always {value} [{file}:{line},{col}]", {
operator: self.operator,
@@ -10732,13 +10791,6 @@ merge(Compressor.prototype, {
});
}
function fuzzy_eval(node, nullish) {
if (node.truthy) return true;
if (node.falsy && !nullish) return false;
if (node.is_truthy()) return true;
return node.evaluate(compressor, true);
}
function is_indexFn(node) {
return node.TYPE == "Call"
&& node.expression instanceof AST_Dot
@@ -11286,7 +11338,8 @@ merge(Compressor.prototype, {
return make_sequence(self, expressions);
}
if (!compressor.option("conditionals")) return self;
var condition = self.condition.is_truthy() || self.condition.evaluate(compressor, true);
if (compressor.option("booleans")) mark_duplicate_condition(compressor, self.condition);
var condition = fuzzy_eval(compressor, self.condition);
if (!condition) {
AST_Node.warn("Condition always false [{file}:{line},{col}]", self.start);
return make_sequence(self, [ self.condition, self.alternative ]).optimize(compressor);