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ast-utils.js
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ast-utils.js
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/**
* @fileoverview Common utils for AST.
* @author Gyandeep Singh
* @copyright jQuery Foundation and other contributors, https://jquery.org/
* MIT License
*/
"use strict";
//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------
var esutils = require("esutils");
//------------------------------------------------------------------------------
// Helpers
//------------------------------------------------------------------------------
var anyFunctionPattern = /^(?:Function(?:Declaration|Expression)|ArrowFunctionExpression)$/;
var arrayOrTypedArrayPattern = /Array$/;
var arrayMethodPattern = /^(?:every|filter|find|findIndex|forEach|map|some)$/;
var bindOrCallOrApplyPattern = /^(?:bind|call|apply)$/;
var breakableTypePattern = /^(?:(?:Do)?While|For(?:In|Of)?|Switch)Statement$/;
var thisTagPattern = /^[\s\*]*@this/m;
/**
* Checks reference if is non initializer and writable.
* @param {Reference} reference - A reference to check.
* @param {int} index - The index of the reference in the references.
* @param {Reference[]} references - The array that the reference belongs to.
* @returns {boolean} Success/Failure
* @private
*/
function isModifyingReference(reference, index, references) {
var identifier = reference.identifier,
modifyingDifferentIdentifier;
/*
* Destructuring assignments can have multiple default value, so
* possibly there are multiple writeable references for the same
* identifier.
*/
modifyingDifferentIdentifier = index === 0 ||
references[index - 1].identifier !== identifier;
return (identifier &&
reference.init === false &&
reference.isWrite() &&
modifyingDifferentIdentifier
);
}
/**
* Checks whether or not a node is a constructor.
* @param {ASTNode} node - A function node to check.
* @returns {boolean} Wehether or not a node is a constructor.
*/
function isES5Constructor(node) {
return (
node.id &&
node.id.name[0] === node.id.name[0].toLocaleUpperCase()
);
}
/**
* Finds a function node from ancestors of a node.
* @param {ASTNode} node - A start node to find.
* @returns {Node|null} A found function node.
*/
function getUpperFunction(node) {
while (node) {
if (anyFunctionPattern.test(node.type)) {
return node;
}
node = node.parent;
}
return null;
}
/**
* Checks whether or not a node is `null` or `undefined`.
* @param {ASTNode} node - A node to check.
* @returns {boolean} Whether or not the node is a `null` or `undefined`.
* @public
*/
function isNullOrUndefined(node) {
return (
(node.type === "Literal" && node.value === null) ||
(node.type === "Identifier" && node.name === "undefined") ||
(node.type === "UnaryExpression" && node.operator === "void")
);
}
/**
* Checks whether or not a node is callee.
* @param {ASTNode} node - A node to check.
* @returns {boolean} Whether or not the node is callee.
*/
function isCallee(node) {
return node.parent.type === "CallExpression" && node.parent.callee === node;
}
/**
* Checks whether or not a node is `Reclect.apply`.
* @param {ASTNode} node - A node to check.
* @returns {boolean} Whether or not the node is a `Reclect.apply`.
*/
function isReflectApply(node) {
return (
node.type === "MemberExpression" &&
node.object.type === "Identifier" &&
node.object.name === "Reflect" &&
node.property.type === "Identifier" &&
node.property.name === "apply" &&
node.computed === false
);
}
/**
* Checks whether or not a node is `Array.from`.
* @param {ASTNode} node - A node to check.
* @returns {boolean} Whether or not the node is a `Array.from`.
*/
function isArrayFromMethod(node) {
return (
node.type === "MemberExpression" &&
node.object.type === "Identifier" &&
arrayOrTypedArrayPattern.test(node.object.name) &&
node.property.type === "Identifier" &&
node.property.name === "from" &&
node.computed === false
);
}
/**
* Checks whether or not a node is a method which has `thisArg`.
* @param {ASTNode} node - A node to check.
* @returns {boolean} Whether or not the node is a method which has `thisArg`.
*/
function isMethodWhichHasThisArg(node) {
while (node) {
if (node.type === "Identifier") {
return arrayMethodPattern.test(node.name);
}
if (node.type === "MemberExpression" && !node.computed) {
node = node.property;
continue;
}
break;
}
return false;
}
/**
* Checks whether or not a node has a `@this` tag in its comments.
* @param {ASTNode} node - A node to check.
* @param {SourceCode} sourceCode - A SourceCode instance to get comments.
* @returns {boolean} Whether or not the node has a `@this` tag in its comments.
*/
function hasJSDocThisTag(node, sourceCode) {
var jsdocComment = sourceCode.getJSDocComment(node);
if (jsdocComment && thisTagPattern.test(jsdocComment.value)) {
return true;
}
// Checks `@this` in its leading comments for callbacks,
// because callbacks don't have its JSDoc comment.
// e.g.
// sinon.test(/* @this sinon.Sandbox */function() { this.spy(); });
return sourceCode.getComments(node).leading.some(function(comment) {
return thisTagPattern.test(comment.value);
});
}
/**
* Determines if a node is surrounded by parentheses.
* @param {RuleContext} context The context object passed to the rule
* @param {ASTNode} node The node to be checked.
* @returns {boolean} True if the node is parenthesised.
* @private
*/
function isParenthesised(context, node) {
var previousToken = context.getTokenBefore(node),
nextToken = context.getTokenAfter(node);
return Boolean(previousToken && nextToken) &&
previousToken.value === "(" && previousToken.range[1] <= node.range[0] &&
nextToken.value === ")" && nextToken.range[0] >= node.range[1];
}
//------------------------------------------------------------------------------
// Public Interface
//------------------------------------------------------------------------------
module.exports = {
/**
* Determines whether two adjacent tokens are on the same line.
* @param {Object} left - The left token object.
* @param {Object} right - The right token object.
* @returns {boolean} Whether or not the tokens are on the same line.
* @public
*/
isTokenOnSameLine: function(left, right) {
return left.loc.end.line === right.loc.start.line;
},
isNullOrUndefined: isNullOrUndefined,
isCallee: isCallee,
isES5Constructor: isES5Constructor,
getUpperFunction: getUpperFunction,
isArrayFromMethod: isArrayFromMethod,
isParenthesised: isParenthesised,
/**
* Checks whether or not a given node is a string literal.
* @param {ASTNode} node - A node to check.
* @returns {boolean} `true` if the node is a string literal.
*/
isStringLiteral: function(node) {
return (
(node.type === "Literal" && typeof node.value === "string") ||
node.type === "TemplateLiteral"
);
},
/**
* Checks whether a given node is a breakable statement or not.
* The node is breakable if the node is one of the following type:
*
* - DoWhileStatement
* - ForInStatement
* - ForOfStatement
* - ForStatement
* - SwitchStatement
* - WhileStatement
*
* @param {ASTNode} node - A node to check.
* @returns {boolean} `true` if the node is breakable.
*/
isBreakableStatement: function(node) {
return breakableTypePattern.test(node.type);
},
/**
* Gets the label if the parent node of a given node is a LabeledStatement.
*
* @param {ASTNode} node - A node to get.
* @returns {string|null} The label or `null`.
*/
getLabel: function(node) {
if (node.parent.type === "LabeledStatement") {
return node.parent.label.name;
}
return null;
},
/**
* Gets references which are non initializer and writable.
* @param {Reference[]} references - An array of references.
* @returns {Reference[]} An array of only references which are non initializer and writable.
* @public
*/
getModifyingReferences: function(references) {
return references.filter(isModifyingReference);
},
/**
* Validate that a string passed in is surrounded by the specified character
* @param {string} val The text to check.
* @param {string} character The character to see if it's surrounded by.
* @returns {boolean} True if the text is surrounded by the character, false if not.
* @private
*/
isSurroundedBy: function(val, character) {
return val[0] === character && val[val.length - 1] === character;
},
/**
* Returns whether the provided node is an ESLint directive comment or not
* @param {LineComment|BlockComment} node The node to be checked
* @returns {boolean} `true` if the node is an ESLint directive comment
*/
isDirectiveComment: function(node) {
var comment = node.value.trim();
return (
node.type === "Line" && comment.indexOf("eslint-") === 0 ||
node.type === "Block" && (
comment.indexOf("global ") === 0 ||
comment.indexOf("eslint ") === 0 ||
comment.indexOf("eslint-") === 0
)
);
},
/**
* Gets the trailing statement of a given node.
*
* if (code)
* consequent;
*
* When taking this `IfStatement`, returns `consequent;` statement.
*
* @param {ASTNode} A node to get.
* @returns {ASTNode|null} The trailing statement's node.
*/
getTrailingStatement: esutils.ast.trailingStatement,
/**
* Finds the variable by a given name in a given scope and its upper scopes.
*
* @param {escope.Scope} initScope - A scope to start find.
* @param {string} name - A variable name to find.
* @returns {escope.Variable|null} A found variable or `null`.
*/
getVariableByName: function(initScope, name) {
var scope = initScope;
while (scope) {
var variable = scope.set.get(name);
if (variable) {
return variable;
}
scope = scope.upper;
}
return null;
},
/**
* Checks whether or not a given function node is the default `this` binding.
*
* First, this checks the node:
*
* - The function name does not start with uppercase (it's a constructor).
* - The function does not have a JSDoc comment that has a @this tag.
*
* Next, this checks the location of the node.
* If the location is below, this judges `this` is valid.
*
* - The location is not on an object literal.
* - The location does not assign to a property.
* - The location is not on an ES2015 class.
* - The location does not call its `bind`/`call`/`apply` method directly.
* - The function is not a callback of array methods (such as `.forEach()`) if `thisArg` is given.
*
* @param {ASTNode} node - A function node to check.
* @param {SourceCode} sourceCode - A SourceCode instance to get comments.
* @returns {boolean} The function node is the default `this` binding.
*/
isDefaultThisBinding: function(node, sourceCode) {
if (isES5Constructor(node) || hasJSDocThisTag(node, sourceCode)) {
return false;
}
while (node) {
var parent = node.parent;
switch (parent.type) {
/*
* Looks up the destination.
* e.g., obj.foo = nativeFoo || function foo() { ... };
*/
case "LogicalExpression":
case "ConditionalExpression":
node = parent;
break;
// If the upper function is IIFE, checks the destination of the return value.
// e.g.
// obj.foo = (function() {
// // setup...
// return function foo() { ... };
// })();
case "ReturnStatement":
var func = getUpperFunction(parent);
if (func === null || !isCallee(func)) {
return true;
}
node = func.parent;
break;
// e.g.
// var obj = { foo() { ... } };
// var obj = { foo: function() { ... } };
case "Property":
return false;
// e.g.
// obj.foo = foo() { ... };
case "AssignmentExpression":
return (
parent.right !== node ||
parent.left.type !== "MemberExpression"
);
// e.g.
// class A { constructor() { ... } }
// class A { foo() { ... } }
// class A { get foo() { ... } }
// class A { set foo() { ... } }
// class A { static foo() { ... } }
case "MethodDefinition":
return false;
// e.g.
// var foo = function foo() { ... }.bind(obj);
// (function foo() { ... }).call(obj);
// (function foo() { ... }).apply(obj, []);
case "MemberExpression":
return (
parent.object !== node ||
parent.property.type !== "Identifier" ||
!bindOrCallOrApplyPattern.test(parent.property.name) ||
!isCallee(parent) ||
parent.parent.arguments.length === 0 ||
isNullOrUndefined(parent.parent.arguments[0])
);
// e.g.
// Reflect.apply(function() {}, obj, []);
// Array.from([], function() {}, obj);
// list.forEach(function() {}, obj);
case "CallExpression":
if (isReflectApply(parent.callee)) {
return (
parent.arguments.length !== 3 ||
parent.arguments[0] !== node ||
isNullOrUndefined(parent.arguments[1])
);
}
if (isArrayFromMethod(parent.callee)) {
return (
parent.arguments.length !== 3 ||
parent.arguments[1] !== node ||
isNullOrUndefined(parent.arguments[2])
);
}
if (isMethodWhichHasThisArg(parent.callee)) {
return (
parent.arguments.length !== 2 ||
parent.arguments[0] !== node ||
isNullOrUndefined(parent.arguments[1])
);
}
return true;
// Otherwise `this` is default.
default:
return true;
}
}
/* istanbul ignore next */
return true;
}
};