var types = require("./types");
var n = types.namedTypes;
var b = types.builders;
var isNumber = types.builtInTypes.number;
var isArray = types.builtInTypes.array;
var Path = require("./path");
var Scope = require("./scope");
function NodePath(value, parentPath, name) {
if (!(this instanceof NodePath)) {
throw new Error("NodePath constructor cannot be invoked without 'new'");
}
Path.call(this, value, parentPath, name);
}
var NPp = NodePath.prototype = Object.create(Path.prototype, {
constructor: {
value: NodePath,
enumerable: false,
writable: true,
configurable: true
}
});
Object.defineProperties(NPp, {
node: {
get: function() {
Object.defineProperty(this, "node", {
configurable: true, // Enable deletion.
value: this._computeNode()
});
return this.node;
}
},
parent: {
get: function() {
Object.defineProperty(this, "parent", {
configurable: true, // Enable deletion.
value: this._computeParent()
});
return this.parent;
}
},
scope: {
get: function() {
Object.defineProperty(this, "scope", {
configurable: true, // Enable deletion.
value: this._computeScope()
});
return this.scope;
}
}
});
NPp.replace = function() {
delete this.node;
delete this.parent;
delete this.scope;
return Path.prototype.replace.apply(this, arguments);
};
NPp.prune = function() {
var remainingNodePath = this.parent;
this.replace();
return cleanUpNodesAfterPrune(remainingNodePath);
};
// The value of the first ancestor Path whose value is a Node.
NPp._computeNode = function() {
var value = this.value;
if (n.Node.check(value)) {
return value;
}
var pp = this.parentPath;
return pp && pp.node || null;
};
// The first ancestor Path whose value is a Node distinct from this.node.
NPp._computeParent = function() {
var value = this.value;
var pp = this.parentPath;
if (!n.Node.check(value)) {
while (pp && !n.Node.check(pp.value)) {
pp = pp.parentPath;
}
if (pp) {
pp = pp.parentPath;
}
}
while (pp && !n.Node.check(pp.value)) {
pp = pp.parentPath;
}
return pp || null;
};
// The closest enclosing scope that governs this node.
NPp._computeScope = function() {
var value = this.value;
var pp = this.parentPath;
var scope = pp && pp.scope;
if (n.Node.check(value) &&
Scope.isEstablishedBy(value)) {
scope = new Scope(this, scope);
}
return scope || null;
};
NPp.getValueProperty = function(name) {
return types.getFieldValue(this.value, name);
};
/**
* Determine whether this.node needs to be wrapped in parentheses in order
* for a parser to reproduce the same local AST structure.
*
* For instance, in the expression `(1 + 2) * 3`, the BinaryExpression
* whose operator is "+" needs parentheses, because `1 + 2 * 3` would
* parse differently.
*
* If assumeExpressionContext === true, we don't worry about edge cases
* like an anonymous FunctionExpression appearing lexically first in its
* enclosing statement and thus needing parentheses to avoid being parsed
* as a FunctionDeclaration with a missing name.
*/
NPp.needsParens = function(assumeExpressionContext) {
var pp = this.parentPath;
if (!pp) {
return false;
}
var node = this.value;
// Only expressions need parentheses.
if (!n.Expression.check(node)) {
return false;
}
// Identifiers never need parentheses.
if (node.type === "Identifier") {
return false;
}
while (!n.Node.check(pp.value)) {
pp = pp.parentPath;
if (!pp) {
return false;
}
}
var parent = pp.value;
switch (node.type) {
case "UnaryExpression":
case "SpreadElement":
case "SpreadProperty":
return parent.type === "MemberExpression"
&& this.name === "object"
&& parent.object === node;
case "BinaryExpression":
case "LogicalExpression":
switch (parent.type) {
case "CallExpression":
return this.name === "callee"
&& parent.callee === node;
case "UnaryExpression":
case "SpreadElement":
case "SpreadProperty":
return true;
case "MemberExpression":
return this.name === "object"
&& parent.object === node;
case "BinaryExpression":
case "LogicalExpression":
var po = parent.operator;
var pp = PRECEDENCE[po];
var no = node.operator;
var np = PRECEDENCE[no];
if (pp > np) {
return true;
}
if (pp === np && this.name === "right") {
if (parent.right !== node) {
throw new Error("Nodes must be equal");
}
return true;
}
default:
return false;
}
case "SequenceExpression":
switch (parent.type) {
case "ForStatement":
// Although parentheses wouldn't hurt around sequence
// expressions in the head of for loops, traditional style
// dictates that e.g. i++, j++ should not be wrapped with
// parentheses.
return false;
case "ExpressionStatement":
return this.name !== "expression";
default:
// Otherwise err on the side of overparenthesization, adding
// explicit exceptions above if this proves overzealous.
return true;
}
case "YieldExpression":
switch (parent.type) {
case "BinaryExpression":
case "LogicalExpression":
case "UnaryExpression":
case "SpreadElement":
case "SpreadProperty":
case "CallExpression":
case "MemberExpression":
case "NewExpression":
case "ConditionalExpression":
case "YieldExpression":
return true;
default:
return false;
}
case "Literal":
return parent.type === "MemberExpression"
&& isNumber.check(node.value)
&& this.name === "object"
&& parent.object === node;
case "AssignmentExpression":
case "ConditionalExpression":
switch (parent.type) {
case "UnaryExpression":
case "SpreadElement":
case "SpreadProperty":
case "BinaryExpression":
case "LogicalExpression":
return true;
case "CallExpression":
return this.name === "callee"
&& parent.callee === node;
case "ConditionalExpression":
return this.name === "test"
&& parent.test === node;
case "MemberExpression":
return this.name === "object"
&& parent.object === node;
default:
return false;
}
default:
if (parent.type === "NewExpression" &&
this.name === "callee" &&
parent.callee === node) {
return containsCallExpression(node);
}
}
if (assumeExpressionContext !== true &&
!this.canBeFirstInStatement() &&
this.firstInStatement())
return true;
return false;
};
function isBinary(node) {
return n.BinaryExpression.check(node)
|| n.LogicalExpression.check(node);
}
function isUnaryLike(node) {
return n.UnaryExpression.check(node)
// I considered making SpreadElement and SpreadProperty subtypes
// of UnaryExpression, but they're not really Expression nodes.
|| (n.SpreadElement && n.SpreadElement.check(node))
|| (n.SpreadProperty && n.SpreadProperty.check(node));
}
var PRECEDENCE = {};
[["||"],
["&&"],
["|"],
["^"],
["&"],
["==", "===", "!=", "!=="],
["<", ">", "<=", ">=", "in", "instanceof"],
[">>", "<<", ">>>"],
["+", "-"],
["*", "/", "%"]
].forEach(function(tier, i) {
tier.forEach(function(op) {
PRECEDENCE[op] = i;
});
});
function containsCallExpression(node) {
if (n.CallExpression.check(node)) {
return true;
}
if (isArray.check(node)) {
return node.some(containsCallExpression);
}
if (n.Node.check(node)) {
return types.someField(node, function(name, child) {
return containsCallExpression(child);
});
}
return false;
}
NPp.canBeFirstInStatement = function() {
var node = this.node;
return !n.FunctionExpression.check(node)
&& !n.ObjectExpression.check(node);
};
NPp.firstInStatement = function() {
return firstInStatement(this);
};
function firstInStatement(path) {
for (var node, parent; path.parent; path = path.parent) {
node = path.node;
parent = path.parent.node;
if (n.BlockStatement.check(parent) &&
path.parent.name === "body" &&
path.name === 0) {
if (parent.body[0] !== node) {
throw new Error("Nodes must be equal");
}
return true;
}
if (n.ExpressionStatement.check(parent) &&
path.name === "expression") {
if (parent.expression !== node) {
throw new Error("Nodes must be equal");
}
return true;
}
if (n.SequenceExpression.check(parent) &&
path.parent.name === "expressions" &&
path.name === 0) {
if (parent.expressions[0] !== node) {
throw new Error("Nodes must be equal");
}
continue;
}
if (n.CallExpression.check(parent) &&
path.name === "callee") {
if (parent.callee !== node) {
throw new Error("Nodes must be equal");
}
continue;
}
if (n.MemberExpression.check(parent) &&
path.name === "object") {
if (parent.object !== node) {
throw new Error("Nodes must be equal");
}
continue;
}
if (n.ConditionalExpression.check(parent) &&
path.name === "test") {
if (parent.test !== node) {
throw new Error("Nodes must be equal");
}
continue;
}
if (isBinary(parent) &&
path.name === "left") {
if (parent.left !== node) {
throw new Error("Nodes must be equal");
}
continue;
}
if (n.UnaryExpression.check(parent) &&
!parent.prefix &&
path.name === "argument") {
if (parent.argument !== node) {
throw new Error("Nodes must be equal");
}
continue;
}
return false;
}
return true;
}
/**
* Pruning certain nodes will result in empty or incomplete nodes, here we clean those nodes up.
*/
function cleanUpNodesAfterPrune(remainingNodePath) {
if (n.VariableDeclaration.check(remainingNodePath.node)) {
var declarations = remainingNodePath.get('declarations').value;
if (!declarations || declarations.length === 0) {
return remainingNodePath.prune();
}
} else if (n.ExpressionStatement.check(remainingNodePath.node)) {
if (!remainingNodePath.get('expression').value) {
return remainingNodePath.prune();
}
} else if (n.IfStatement.check(remainingNodePath.node)) {
cleanUpIfStatementAfterPrune(remainingNodePath);
}
return remainingNodePath;
}
function cleanUpIfStatementAfterPrune(ifStatement) {
var testExpression = ifStatement.get('test').value;
var alternate = ifStatement.get('alternate').value;
var consequent = ifStatement.get('consequent').value;
if (!consequent && !alternate) {
var testExpressionStatement = b.expressionStatement(testExpression);
ifStatement.replace(testExpressionStatement);
} else if (!consequent && alternate) {
var negatedTestExpression = b.unaryExpression('!', testExpression, true);
if (n.UnaryExpression.check(testExpression) && testExpression.operator === '!') {
negatedTestExpression = testExpression.argument;
}
ifStatement.get("test").replace(negatedTestExpression);
ifStatement.get("consequent").replace(alternate);
ifStatement.get("alternate").replace();
}
}
module.exports = NodePath;