267 lines
8.6 KiB
JavaScript
267 lines
8.6 KiB
JavaScript
/**
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* @fileoverview Rule to flag use of variables before they are defined
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* @author Ilya Volodin
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*/
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"use strict";
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//------------------------------------------------------------------------------
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// Helpers
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//------------------------------------------------------------------------------
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const SENTINEL_TYPE = /^(?:(?:Function|Class)(?:Declaration|Expression)|ArrowFunctionExpression|CatchClause|ImportDeclaration|ExportNamedDeclaration)$/;
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const FOR_IN_OF_TYPE = /^For(?:In|Of)Statement$/;
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/**
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* Parses a given value as options.
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*
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* @param {any} options - A value to parse.
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* @returns {Object} The parsed options.
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*/
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function parseOptions(options) {
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let functions = true;
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let classes = true;
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let variables = true;
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if (typeof options === "string") {
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functions = (options !== "nofunc");
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} else if (typeof options === "object" && options !== null) {
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functions = options.functions !== false;
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classes = options.classes !== false;
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variables = options.variables !== false;
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}
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return { functions, classes, variables };
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}
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/**
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* Checks whether or not a given variable is a function declaration.
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*
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* @param {eslint-scope.Variable} variable - A variable to check.
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* @returns {boolean} `true` if the variable is a function declaration.
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*/
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function isFunction(variable) {
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return variable.defs[0].type === "FunctionName";
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}
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/**
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* Checks whether or not a given variable is a class declaration in an upper function scope.
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*
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* @param {eslint-scope.Variable} variable - A variable to check.
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* @param {eslint-scope.Reference} reference - A reference to check.
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* @returns {boolean} `true` if the variable is a class declaration.
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*/
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function isOuterClass(variable, reference) {
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return (
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variable.defs[0].type === "ClassName" &&
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variable.scope.variableScope !== reference.from.variableScope
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);
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}
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/**
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* Checks whether or not a given variable is a variable declaration in an upper function scope.
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* @param {eslint-scope.Variable} variable - A variable to check.
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* @param {eslint-scope.Reference} reference - A reference to check.
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* @returns {boolean} `true` if the variable is a variable declaration.
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*/
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function isOuterVariable(variable, reference) {
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return (
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variable.defs[0].type === "Variable" &&
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variable.scope.variableScope !== reference.from.variableScope
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);
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}
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/**
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* Checks whether or not a given location is inside of the range of a given node.
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*
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* @param {ASTNode} node - An node to check.
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* @param {number} location - A location to check.
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* @returns {boolean} `true` if the location is inside of the range of the node.
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*/
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function isInRange(node, location) {
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return node && node.range[0] <= location && location <= node.range[1];
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}
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/**
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* Checks whether or not a given reference is inside of the initializers of a given variable.
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*
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* This returns `true` in the following cases:
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*
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* var a = a
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* var [a = a] = list
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* var {a = a} = obj
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* for (var a in a) {}
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* for (var a of a) {}
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*
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* @param {Variable} variable - A variable to check.
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* @param {Reference} reference - A reference to check.
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* @returns {boolean} `true` if the reference is inside of the initializers.
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*/
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function isInInitializer(variable, reference) {
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if (variable.scope !== reference.from) {
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return false;
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}
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let node = variable.identifiers[0].parent;
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const location = reference.identifier.range[1];
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while (node) {
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if (node.type === "VariableDeclarator") {
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if (isInRange(node.init, location)) {
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return true;
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}
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if (FOR_IN_OF_TYPE.test(node.parent.parent.type) &&
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isInRange(node.parent.parent.right, location)
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) {
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return true;
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}
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break;
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} else if (node.type === "AssignmentPattern") {
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if (isInRange(node.right, location)) {
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return true;
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}
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} else if (SENTINEL_TYPE.test(node.type)) {
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break;
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}
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node = node.parent;
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}
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return false;
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}
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//------------------------------------------------------------------------------
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// Rule Definition
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//------------------------------------------------------------------------------
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module.exports = {
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meta: {
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docs: {
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description: "disallow the use of variables before they are defined",
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category: "Variables",
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recommended: false
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},
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schema: [
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{
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oneOf: [
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{
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enum: ["nofunc"]
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},
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{
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type: "object",
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properties: {
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functions: { type: "boolean" },
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classes: { type: "boolean" },
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variables: { type: "boolean" }
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},
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additionalProperties: false
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}
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]
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}
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]
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},
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create(context) {
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const options = parseOptions(context.options[0]);
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/**
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* Determines whether a given use-before-define case should be reported according to the options.
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* @param {eslint-scope.Variable} variable The variable that gets used before being defined
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* @param {eslint-scope.Reference} reference The reference to the variable
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* @returns {boolean} `true` if the usage should be reported
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*/
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function isForbidden(variable, reference) {
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if (isFunction(variable)) {
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return options.functions;
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}
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if (isOuterClass(variable, reference)) {
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return options.classes;
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}
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if (isOuterVariable(variable, reference)) {
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return options.variables;
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}
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return true;
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}
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/**
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* Finds and validates all variables in a given scope.
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* @param {Scope} scope The scope object.
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* @returns {void}
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* @private
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*/
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function findVariablesInScope(scope) {
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scope.references.forEach(reference => {
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const variable = reference.resolved;
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/*
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* Skips when the reference is:
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* - initialization's.
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* - referring to an undefined variable.
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* - referring to a global environment variable (there're no identifiers).
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* - located preceded by the variable (except in initializers).
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* - allowed by options.
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*/
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if (reference.init ||
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!variable ||
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variable.identifiers.length === 0 ||
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(variable.identifiers[0].range[1] < reference.identifier.range[1] && !isInInitializer(variable, reference)) ||
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!isForbidden(variable, reference)
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) {
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return;
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}
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// Reports.
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context.report({
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node: reference.identifier,
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message: "'{{name}}' was used before it was defined.",
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data: reference.identifier
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});
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});
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}
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/**
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* Validates variables inside of a node's scope.
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* @param {ASTNode} node The node to check.
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* @returns {void}
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* @private
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*/
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function findVariables() {
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const scope = context.getScope();
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findVariablesInScope(scope);
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}
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const ruleDefinition = {
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"Program:exit"(node) {
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const scope = context.getScope(),
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ecmaFeatures = context.parserOptions.ecmaFeatures || {};
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findVariablesInScope(scope);
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// both Node.js and Modules have an extra scope
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if (ecmaFeatures.globalReturn || node.sourceType === "module") {
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findVariablesInScope(scope.childScopes[0]);
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}
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}
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};
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if (context.parserOptions.ecmaVersion >= 6) {
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ruleDefinition["BlockStatement:exit"] =
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ruleDefinition["SwitchStatement:exit"] = findVariables;
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ruleDefinition["ArrowFunctionExpression:exit"] = function(node) {
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if (node.body.type !== "BlockStatement") {
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findVariables();
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}
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};
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} else {
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ruleDefinition["FunctionExpression:exit"] =
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ruleDefinition["FunctionDeclaration:exit"] =
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ruleDefinition["ArrowFunctionExpression:exit"] = findVariables;
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}
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return ruleDefinition;
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}
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};
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