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"use strict";
const evaluate = require("babel-helper-evaluate-path");
function isPureAndUndefined(rval, {
tdz,
scope = {
hasBinding: () => false
}
} = {}) {
if (rval.isIdentifier() && rval.node.name === "undefined") {
// deopt right away if undefined is a local binding
if (scope.hasBinding(rval.node.name, true
/* no globals */
)) {
return false;
}
return true;
}
if (!rval.isPure()) {
return false;
}
const evaluation = evaluate(rval, {
tdz
});
return evaluation.confident === true && evaluation.value === undefined;
}
function getLoopParent(path, scopeParent) {
const parent = path.findParent(p => p.isLoop() || p === scopeParent); // don't traverse higher than the function the var is defined in.
return parent === scopeParent ? null : parent;
}
function getFunctionParent(path, scopeParent) {
const parent = path.findParent(p => p.isFunction()); // don't traverse higher than the function the var is defined in.
return parent === scopeParent ? null : parent;
}
function getFunctionReferences(path, scopeParent, references = new Set()) {
for (let func = getFunctionParent(path, scopeParent); func; func = getFunctionParent(func, scopeParent)) {
const id = func.node.id;
const binding = id && func.scope.getBinding(id.name);
if (!binding) {
continue;
}
binding.referencePaths.forEach(path => {
if (!references.has(path)) {
references.add(path);
getFunctionReferences(path, scopeParent, references);
}
});
}
return references;
}
function hasViolation(declarator, scope, start) {
const binding = scope.getBinding(declarator.node.id.name);
if (!binding) {
return true;
}
const scopeParent = declarator.getFunctionParent();
const violation = binding.constantViolations.some(v => {
// https://github.com/babel/minify/issues/630
if (!v.node) {
return false;
} // return 'true' if we cannot guarantee the violation references
// the initialized identifier after
const violationStart = v.node.start;
if (violationStart === undefined || violationStart < start) {
return true;
}
const references = getFunctionReferences(v, scopeParent);
var _iteratorNormalCompletion = true;
var _didIteratorError = false;
var _iteratorError = undefined;
try {
for (var _iterator = references[Symbol.iterator](), _step; !(_iteratorNormalCompletion = (_step = _iterator.next()).done); _iteratorNormalCompletion = true) {
const ref = _step.value;
if (ref.node.start === undefined || ref.node.start < start) {
return true;
}
}
} catch (err) {
_didIteratorError = true;
_iteratorError = err;
} finally {
try {
if (!_iteratorNormalCompletion && _iterator.return != null) {
_iterator.return();
}
} finally {
if (_didIteratorError) {
throw _iteratorError;
}
}
}
for (let loop = getLoopParent(declarator, scopeParent); loop; loop = getLoopParent(loop, scopeParent)) {
if (loop.node.end === undefined || loop.node.end > violationStart) {
return true;
}
}
});
return violation;
}
module.exports = function () {
return {
name: "transform-remove-undefined",
visitor: {
SequenceExpression(path, {
opts: {
tdz
} = {}
}) {
const expressions = path.get("expressions");
for (let i = 0; i < expressions.length; i++) {
const expr = expressions[i];
if (!isPureAndUndefined(expr, {
tdz,
scope: path.scope
})) continue; // last value
if (i === expressions.length - 1) {
if (path.parentPath.isExpressionStatement()) {
expr.remove();
}
} else {
expr.remove();
}
}
},
ReturnStatement(path, {
opts: {
tdz
} = {}
}) {
if (path.node.argument !== null) {
if (isPureAndUndefined(path.get("argument"), {
tdz,
scope: path.scope
})) {
path.node.argument = null;
}
}
},
VariableDeclaration(path, {
opts: {
tdz
} = {}
}) {
switch (path.node.kind) {
case "const":
break;
case "let":
var _iteratorNormalCompletion2 = true;
var _didIteratorError2 = false;
var _iteratorError2 = undefined;
try {
for (var _iterator2 = path.get("declarations")[Symbol.iterator](), _step2; !(_iteratorNormalCompletion2 = (_step2 = _iterator2.next()).done); _iteratorNormalCompletion2 = true) {
const declarator = _step2.value;
if (isPureAndUndefined(declarator.get("init"), {
tdz
})) {
declarator.node.init = null;
}
}
} catch (err) {
_didIteratorError2 = true;
_iteratorError2 = err;
} finally {
try {
if (!_iteratorNormalCompletion2 && _iterator2.return != null) {
_iterator2.return();
}
} finally {
if (_didIteratorError2) {
throw _iteratorError2;
}
}
}
break;
case "var":
const start = path.node.start;
if (start === undefined) {
// This is common for plugin-generated nodes
break;
}
const scope = path.scope;
var _iteratorNormalCompletion3 = true;
var _didIteratorError3 = false;
var _iteratorError3 = undefined;
try {
for (var _iterator3 = path.get("declarations")[Symbol.iterator](), _step3; !(_iteratorNormalCompletion3 = (_step3 = _iterator3.next()).done); _iteratorNormalCompletion3 = true) {
const declarator = _step3.value;
if (isPureAndUndefined(declarator.get("init")) && !hasViolation(declarator, scope, start)) {
declarator.node.init = null;
}
}
} catch (err) {
_didIteratorError3 = true;
_iteratorError3 = err;
} finally {
try {
if (!_iteratorNormalCompletion3 && _iterator3.return != null) {
_iterator3.return();
}
} finally {
if (_didIteratorError3) {
throw _iteratorError3;
}
}
}
break;
}
}
}
};
};
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