fast-path.js

"use strict";
Object.defineProperty(exports, "__esModule", { value: true });
var tslib_1 = require("tslib");
var assert_1 = tslib_1.__importDefault(require("assert"));
var types = tslib_1.__importStar(require("ast-types"));
var util = tslib_1.__importStar(require("./util"));
var n = types.namedTypes;
var isArray = types.builtInTypes.array;
var isNumber = types.builtInTypes.number;
var PRECEDENCE = {};
[
    ["??"],
    ["||"],
    ["&&"],
    ["|"],
    ["^"],
    ["&"],
    ["==", "===", "!=", "!=="],
    ["<", ">", "<=", ">=", "in", "instanceof"],
    [">>", "<<", ">>>"],
    ["+", "-"],
    ["*", "/", "%"],
    ["**"],
].forEach(function (tier, i) {
    tier.forEach(function (op) {
        PRECEDENCE[op] = i;
    });
});
var FastPath = function FastPath(value) {
    assert_1.default.ok(this instanceof FastPath);
    this.stack = [value];
};
var FPp = FastPath.prototype;
// Static convenience function for coercing a value to a FastPath.
FastPath.from = function (obj) {
    if (obj instanceof FastPath) {
        // Return a defensive copy of any existing FastPath instances.
        return obj.copy();
    }
    if (obj instanceof types.NodePath) {
        // For backwards compatibility, unroll NodePath instances into
        // lightweight FastPath [..., name, value] stacks.
        var copy = Object.create(FastPath.prototype);
        var stack = [obj.value];
        for (var pp = void 0; (pp = obj.parentPath); obj = pp)
            stack.push(obj.name, pp.value);
        copy.stack = stack.reverse();
        return copy;
    }
    // Otherwise use obj as the value of the new FastPath instance.
    return new FastPath(obj);
};
FPp.copy = function copy() {
    var copy = Object.create(FastPath.prototype);
    copy.stack = this.stack.slice(0);
    return copy;
};
// The name of the current property is always the penultimate element of
// this.stack, and always a String.
FPp.getName = function getName() {
    var s = this.stack;
    var len = s.length;
    if (len > 1) {
        return s[len - 2];
    }
    // Since the name is always a string, null is a safe sentinel value to
    // return if we do not know the name of the (root) value.
    return null;
};
// The value of the current property is always the final element of
// this.stack.
FPp.getValue = function getValue() {
    var s = this.stack;
    return s[s.length - 1];
};
FPp.valueIsDuplicate = function () {
    var s = this.stack;
    var valueIndex = s.length - 1;
    return s.lastIndexOf(s[valueIndex], valueIndex - 1) >= 0;
};
function getNodeHelper(path, count) {
    var s = path.stack;
    for (var i = s.length - 1; i >= 0; i -= 2) {
        var value = s[i];
        if (n.Node.check(value) && --count < 0) {
            return value;
        }
    }
    return null;
}
FPp.getNode = function getNode(count) {
    if (count === void 0) { count = 0; }
    return getNodeHelper(this, ~~count);
};
FPp.getParentNode = function getParentNode(count) {
    if (count === void 0) { count = 0; }
    return getNodeHelper(this, ~~count + 1);
};
// The length of the stack can be either even or odd, depending on whether
// or not we have a name for the root value. The difference between the
// index of the root value and the index of the final value is always
// even, though, which allows us to return the root value in constant time
// (i.e. without iterating backwards through the stack).
FPp.getRootValue = function getRootValue() {
    var s = this.stack;
    if (s.length % 2 === 0) {
        return s[1];
    }
    return s[0];
};
// Temporarily push properties named by string arguments given after the
// callback function onto this.stack, then call the callback with a
// reference to this (modified) FastPath object. Note that the stack will
// be restored to its original state after the callback is finished, so it
// is probably a mistake to retain a reference to the path.
FPp.call = function call(callback /*, name1, name2, ... */) {
    var s = this.stack;
    var origLen = s.length;
    var value = s[origLen - 1];
    var argc = arguments.length;
    for (var i = 1; i < argc; ++i) {
        var name = arguments[i];
        value = value[name];
        s.push(name, value);
    }
    var result = callback(this);
    s.length = origLen;
    return result;
};
// Similar to FastPath.prototype.call, except that the value obtained by
// accessing this.getValue()[name1][name2]... should be array-like. The
// callback will be called with a reference to this path object for each
// element of the array.
FPp.each = function each(callback /*, name1, name2, ... */) {
    var s = this.stack;
    var origLen = s.length;
    var value = s[origLen - 1];
    var argc = arguments.length;
    for (var i = 1; i < argc; ++i) {
        var name = arguments[i];
        value = value[name];
        s.push(name, value);
    }
    for (var i = 0; i < value.length; ++i) {
        if (i in value) {
            s.push(i, value[i]);
            // If the callback needs to know the value of i, call
            // path.getName(), assuming path is the parameter name.
            callback(this);
            s.length -= 2;
        }
    }
    s.length = origLen;
};
// Similar to FastPath.prototype.each, except that the results of the
// callback function invocations are stored in an array and returned at
// the end of the iteration.
FPp.map = function map(callback /*, name1, name2, ... */) {
    var s = this.stack;
    var origLen = s.length;
    var value = s[origLen - 1];
    var argc = arguments.length;
    for (var i = 1; i < argc; ++i) {
        var name = arguments[i];
        value = value[name];
        s.push(name, value);
    }
    var result = new Array(value.length);
    for (var i = 0; i < value.length; ++i) {
        if (i in value) {
            s.push(i, value[i]);
            result[i] = callback(this, i);
            s.length -= 2;
        }
    }
    s.length = origLen;
    return result;
};
// Returns true if the node at the tip of the path is wrapped with
// parentheses, OR if the only reason the node needed parentheses was that
// it couldn't be the first expression in the enclosing statement (see
// FastPath#canBeFirstInStatement), and it has an opening `(` character.
// For example, the FunctionExpression in `(function(){}())` appears to
// need parentheses only because it's the first expression in the AST, but
// since it happens to be preceded by a `(` (which is not apparent from
// the AST but can be determined using FastPath#getPrevToken), there is no
// ambiguity about how to parse it, so it counts as having parentheses,
// even though it is not immediately followed by a `)`.
FPp.hasParens = function () {
    var node = this.getNode();
    var prevToken = this.getPrevToken(node);
    if (!prevToken) {
        return false;
    }
    var nextToken = this.getNextToken(node);
    if (!nextToken) {
        return false;
    }
    if (prevToken.value === "(") {
        if (nextToken.value === ")") {
            // If the node preceded by a `(` token and followed by a `)` token,
            // then of course it has parentheses.
            return true;
        }
        // If this is one of the few Expression types that can't come first in
        // the enclosing statement because of parsing ambiguities (namely,
        // FunctionExpression, ObjectExpression, and ClassExpression) and
        // this.firstInStatement() returns true, and the node would not need
        // parentheses in an expression context because this.needsParens(true)
        // returns false, then it just needs an opening parenthesis to resolve
        // the parsing ambiguity that made it appear to need parentheses.
        var justNeedsOpeningParen = !this.canBeFirstInStatement() &&
            this.firstInStatement() &&
            !this.needsParens(true);
        if (justNeedsOpeningParen) {
            return true;
        }
    }
    return false;
};
FPp.getPrevToken = function (node) {
    node = node || this.getNode();
    var loc = node && node.loc;
    var tokens = loc && loc.tokens;
    if (tokens && loc.start.token > 0) {
        var token = tokens[loc.start.token - 1];
        if (token) {
            // Do not return tokens that fall outside the root subtree.
            var rootLoc = this.getRootValue().loc;
            if (util.comparePos(rootLoc.start, token.loc.start) <= 0) {
                return token;
            }
        }
    }
    return null;
};
FPp.getNextToken = function (node) {
    node = node || this.getNode();
    var loc = node && node.loc;
    var tokens = loc && loc.tokens;
    if (tokens && loc.end.token < tokens.length) {
        var token = tokens[loc.end.token];
        if (token) {
            // Do not return tokens that fall outside the root subtree.
            var rootLoc = this.getRootValue().loc;
            if (util.comparePos(token.loc.end, rootLoc.end) <= 0) {
                return token;
            }
        }
    }
    return null;
};
// Inspired by require("ast-types").NodePath.prototype.needsParens, but
// more efficient because we're iterating backwards through a stack.
FPp.needsParens = function (assumeExpressionContext) {
    var node = this.getNode();
    // This needs to come before `if (!parent) { return false }` because
    // an object destructuring assignment requires parens for
    // correctness even when it's the topmost expression.
    if (node.type === "AssignmentExpression" &&
        node.left.type === "ObjectPattern") {
        return true;
    }
    var parent = this.getParentNode();
    var name = this.getName();
    // If the value of this path is some child of a Node and not a Node
    // itself, then it doesn't need parentheses. Only Node objects (in fact,
    // only Expression nodes) need parentheses.
    if (this.getValue() !== node) {
        return false;
    }
    // Only statements don't need parentheses.
    if (n.Statement.check(node)) {
        return false;
    }
    // Identifiers never need parentheses.
    if (node.type === "Identifier") {
        return false;
    }
    if (parent && parent.type === "ParenthesizedExpression") {
        return false;
    }
    if (node.extra && node.extra.parenthesized) {
        return true;
    }
    if (!parent)
        return false;
    switch (node.type) {
        case "UnaryExpression":
        case "SpreadElement":
        case "SpreadProperty":
            return (parent.type === "MemberExpression" &&
                name === "object" &&
                parent.object === node);
        case "BinaryExpression":
        case "LogicalExpression":
            switch (parent.type) {
                case "CallExpression":
                    return name === "callee" && parent.callee === node;
                case "UnaryExpression":
                case "SpreadElement":
                case "SpreadProperty":
                    return true;
                case "MemberExpression":
                    return 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 && name === "right") {
                        assert_1.default.strictEqual(parent.right, node);
                        return true;
                    }
                    break;
                }
                default:
                    return false;
            }
            break;
        case "SequenceExpression":
            switch (parent.type) {
                case "ReturnStatement":
                    return false;
                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 name !== "expression";
                default:
                    // Otherwise err on the side of overparenthesization, adding
                    // explicit exceptions above if this proves overzealous.
                    return true;
            }
        case "OptionalIndexedAccessType":
            return node.optional && parent.type === "IndexedAccessType";
        case "IntersectionTypeAnnotation":
        case "UnionTypeAnnotation":
            return parent.type === "NullableTypeAnnotation";
        case "Literal":
            return (parent.type === "MemberExpression" &&
                isNumber.check(node.value) &&
                name === "object" &&
                parent.object === node);
        // Babel 6 Literal split
        case "NumericLiteral":
            return (parent.type === "MemberExpression" &&
                name === "object" &&
                parent.object === node);
        case "YieldExpression":
        case "AwaitExpression":
        case "AssignmentExpression":
        case "ConditionalExpression":
            switch (parent.type) {
                case "UnaryExpression":
                case "SpreadElement":
                case "SpreadProperty":
                case "BinaryExpression":
                case "LogicalExpression":
                    return true;
                case "CallExpression":
                case "NewExpression":
                    return name === "callee" && parent.callee === node;
                case "ConditionalExpression":
                    return name === "test" && parent.test === node;
                case "MemberExpression":
                    return name === "object" && parent.object === node;
                default:
                    return false;
            }
        case "ArrowFunctionExpression":
            if (n.CallExpression.check(parent) &&
                name === "callee" &&
                parent.callee === node) {
                return true;
            }
            if (n.MemberExpression.check(parent) &&
                name === "object" &&
                parent.object === node) {
                return true;
            }
            if (n.TSAsExpression &&
                n.TSAsExpression.check(parent) &&
                name === "expression" &&
                parent.expression === node) {
                return true;
            }
            return isBinary(parent);
        case "ObjectExpression":
            if (parent.type === "ArrowFunctionExpression" &&
                name === "body" &&
                parent.body === node) {
                return true;
            }
            break;
        case "TSAsExpression":
            if (parent.type === "ArrowFunctionExpression" &&
                name === "body" &&
                parent.body === node &&
                node.expression.type === "ObjectExpression") {
                return true;
            }
            break;
        case "CallExpression":
            if (name === "declaration" &&
                n.ExportDefaultDeclaration.check(parent) &&
                n.FunctionExpression.check(node.callee)) {
                return true;
            }
    }
    if (parent.type === "NewExpression" &&
        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);
}
// @ts-ignore 'isUnaryLike' is declared but its value is never read. [6133]
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)));
}
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;
}
FPp.canBeFirstInStatement = function () {
    var node = this.getNode();
    if (n.FunctionExpression.check(node)) {
        return false;
    }
    if (n.ObjectExpression.check(node)) {
        return false;
    }
    if (n.ClassExpression.check(node)) {
        return false;
    }
    return true;
};
FPp.firstInStatement = function () {
    var s = this.stack;
    var parentName, parent;
    var childName, child;
    for (var i = s.length - 1; i >= 0; i -= 2) {
        if (n.Node.check(s[i])) {
            childName = parentName;
            child = parent;
            parentName = s[i - 1];
            parent = s[i];
        }
        if (!parent || !child) {
            continue;
        }
        if (n.BlockStatement.check(parent) &&
            parentName === "body" &&
            childName === 0) {
            assert_1.default.strictEqual(parent.body[0], child);
            return true;
        }
        if (n.ExpressionStatement.check(parent) && childName === "expression") {
            assert_1.default.strictEqual(parent.expression, child);
            return true;
        }
        if (n.AssignmentExpression.check(parent) && childName === "left") {
            assert_1.default.strictEqual(parent.left, child);
            return true;
        }
        if (n.ArrowFunctionExpression.check(parent) && childName === "body") {
            assert_1.default.strictEqual(parent.body, child);
            return true;
        }
        // s[i + 1] and s[i + 2] represent the array between the parent
        // SequenceExpression node and its child nodes
        if (n.SequenceExpression.check(parent) &&
            s[i + 1] === "expressions" &&
            childName === 0) {
            assert_1.default.strictEqual(parent.expressions[0], child);
            continue;
        }
        if (n.CallExpression.check(parent) && childName === "callee") {
            assert_1.default.strictEqual(parent.callee, child);
            continue;
        }
        if (n.MemberExpression.check(parent) && childName === "object") {
            assert_1.default.strictEqual(parent.object, child);
            continue;
        }
        if (n.ConditionalExpression.check(parent) && childName === "test") {
            assert_1.default.strictEqual(parent.test, child);
            continue;
        }
        if (isBinary(parent) && childName === "left") {
            assert_1.default.strictEqual(parent.left, child);
            continue;
        }
        if (n.UnaryExpression.check(parent) &&
            !parent.prefix &&
            childName === "argument") {
            assert_1.default.strictEqual(parent.argument, child);
            continue;
        }
        return false;
    }
    return true;
};
exports.default = FastPath;