278 lines
10 KiB
JavaScript
278 lines
10 KiB
JavaScript
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/**
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* @fileoverview Rule to control usage of strict mode directives.
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* @author Brandon Mills
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*/
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"use strict";
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//------------------------------------------------------------------------------
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// Requirements
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//------------------------------------------------------------------------------
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const astUtils = require("../ast-utils");
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//------------------------------------------------------------------------------
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// Helpers
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//------------------------------------------------------------------------------
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const messages = {
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function: "Use the function form of 'use strict'.",
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global: "Use the global form of 'use strict'.",
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multiple: "Multiple 'use strict' directives.",
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never: "Strict mode is not permitted.",
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unnecessary: "Unnecessary 'use strict' directive.",
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module: "'use strict' is unnecessary inside of modules.",
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implied: "'use strict' is unnecessary when implied strict mode is enabled.",
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unnecessaryInClasses: "'use strict' is unnecessary inside of classes.",
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nonSimpleParameterList: "'use strict' directive inside a function with non-simple parameter list throws a syntax error since ES2016.",
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wrap: "Wrap {{name}} in a function with 'use strict' directive."
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};
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/**
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* Gets all of the Use Strict Directives in the Directive Prologue of a group of
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* statements.
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* @param {ASTNode[]} statements Statements in the program or function body.
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* @returns {ASTNode[]} All of the Use Strict Directives.
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*/
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function getUseStrictDirectives(statements) {
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const directives = [];
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for (let i = 0; i < statements.length; i++) {
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const statement = statements[i];
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if (
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statement.type === "ExpressionStatement" &&
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statement.expression.type === "Literal" &&
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statement.expression.value === "use strict"
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) {
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directives[i] = statement;
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} else {
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break;
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}
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}
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return directives;
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}
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/**
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* Checks whether a given parameter is a simple parameter.
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*
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* @param {ASTNode} node - A pattern node to check.
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* @returns {boolean} `true` if the node is an Identifier node.
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*/
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function isSimpleParameter(node) {
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return node.type === "Identifier";
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}
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/**
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* Checks whether a given parameter list is a simple parameter list.
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*
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* @param {ASTNode[]} params - A parameter list to check.
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* @returns {boolean} `true` if the every parameter is an Identifier node.
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*/
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function isSimpleParameterList(params) {
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return params.every(isSimpleParameter);
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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: "require or disallow strict mode directives",
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category: "Strict Mode",
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recommended: false
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},
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schema: [
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{
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enum: ["never", "global", "function", "safe"]
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}
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],
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fixable: "code"
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},
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create(context) {
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const ecmaFeatures = context.parserOptions.ecmaFeatures || {},
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scopes = [],
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classScopes = [];
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let mode = context.options[0] || "safe";
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if (ecmaFeatures.impliedStrict) {
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mode = "implied";
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} else if (mode === "safe") {
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mode = ecmaFeatures.globalReturn ? "global" : "function";
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}
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/**
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* Determines whether a reported error should be fixed, depending on the error type.
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* @param {string} errorType The type of error
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* @returns {boolean} `true` if the reported error should be fixed
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*/
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function shouldFix(errorType) {
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return errorType === "multiple" || errorType === "unnecessary" || errorType === "module" || errorType === "implied" || errorType === "unnecessaryInClasses";
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}
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/**
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* Gets a fixer function to remove a given 'use strict' directive.
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* @param {ASTNode} node The directive that should be removed
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* @returns {Function} A fixer function
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*/
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function getFixFunction(node) {
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return fixer => fixer.remove(node);
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}
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/**
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* Report a slice of an array of nodes with a given message.
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* @param {ASTNode[]} nodes Nodes.
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* @param {string} start Index to start from.
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* @param {string} end Index to end before.
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* @param {string} message Message to display.
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* @param {boolean} fix `true` if the directive should be fixed (i.e. removed)
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* @returns {void}
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*/
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function reportSlice(nodes, start, end, message, fix) {
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nodes.slice(start, end).forEach(node => {
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context.report({ node, message, fix: fix ? getFixFunction(node) : null });
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});
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}
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/**
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* Report all nodes in an array with a given message.
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* @param {ASTNode[]} nodes Nodes.
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* @param {string} message Message to display.
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* @param {boolean} fix `true` if the directive should be fixed (i.e. removed)
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* @returns {void}
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*/
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function reportAll(nodes, message, fix) {
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reportSlice(nodes, 0, nodes.length, message, fix);
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}
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/**
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* Report all nodes in an array, except the first, with a given message.
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* @param {ASTNode[]} nodes Nodes.
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* @param {string} message Message to display.
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* @param {boolean} fix `true` if the directive should be fixed (i.e. removed)
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* @returns {void}
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*/
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function reportAllExceptFirst(nodes, message, fix) {
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reportSlice(nodes, 1, nodes.length, message, fix);
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}
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/**
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* Entering a function in 'function' mode pushes a new nested scope onto the
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* stack. The new scope is true if the nested function is strict mode code.
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* @param {ASTNode} node The function declaration or expression.
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* @param {ASTNode[]} useStrictDirectives The Use Strict Directives of the node.
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* @returns {void}
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*/
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function enterFunctionInFunctionMode(node, useStrictDirectives) {
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const isInClass = classScopes.length > 0,
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isParentGlobal = scopes.length === 0 && classScopes.length === 0,
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isParentStrict = scopes.length > 0 && scopes[scopes.length - 1],
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isStrict = useStrictDirectives.length > 0;
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if (isStrict) {
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if (!isSimpleParameterList(node.params)) {
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context.report({ node: useStrictDirectives[0], message: messages.nonSimpleParameterList });
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} else if (isParentStrict) {
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context.report({ node: useStrictDirectives[0], message: messages.unnecessary, fix: getFixFunction(useStrictDirectives[0]) });
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} else if (isInClass) {
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context.report({ node: useStrictDirectives[0], message: messages.unnecessaryInClasses, fix: getFixFunction(useStrictDirectives[0]) });
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}
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reportAllExceptFirst(useStrictDirectives, messages.multiple, true);
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} else if (isParentGlobal) {
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if (isSimpleParameterList(node.params)) {
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context.report({ node, message: messages.function });
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} else {
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context.report({
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node,
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message: messages.wrap,
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data: { name: astUtils.getFunctionNameWithKind(node) }
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});
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}
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}
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scopes.push(isParentStrict || isStrict);
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}
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/**
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* Exiting a function in 'function' mode pops its scope off the stack.
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* @returns {void}
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*/
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function exitFunctionInFunctionMode() {
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scopes.pop();
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}
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/**
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* Enter a function and either:
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* - Push a new nested scope onto the stack (in 'function' mode).
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* - Report all the Use Strict Directives (in the other modes).
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* @param {ASTNode} node The function declaration or expression.
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* @returns {void}
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*/
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function enterFunction(node) {
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const isBlock = node.body.type === "BlockStatement",
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useStrictDirectives = isBlock
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? getUseStrictDirectives(node.body.body) : [];
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if (mode === "function") {
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enterFunctionInFunctionMode(node, useStrictDirectives);
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} else if (useStrictDirectives.length > 0) {
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if (isSimpleParameterList(node.params)) {
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reportAll(useStrictDirectives, messages[mode], shouldFix(mode));
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} else {
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context.report({ node: useStrictDirectives[0], message: messages.nonSimpleParameterList });
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reportAllExceptFirst(useStrictDirectives, messages.multiple, true);
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}
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}
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}
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const rule = {
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Program(node) {
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const useStrictDirectives = getUseStrictDirectives(node.body);
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if (node.sourceType === "module") {
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mode = "module";
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}
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if (mode === "global") {
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if (node.body.length > 0 && useStrictDirectives.length === 0) {
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context.report({ node, message: messages.global });
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}
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reportAllExceptFirst(useStrictDirectives, messages.multiple, true);
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} else {
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reportAll(useStrictDirectives, messages[mode], shouldFix(mode));
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}
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},
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FunctionDeclaration: enterFunction,
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FunctionExpression: enterFunction,
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ArrowFunctionExpression: enterFunction
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};
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if (mode === "function") {
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Object.assign(rule, {
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// Inside of class bodies are always strict mode.
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ClassBody() {
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classScopes.push(true);
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},
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"ClassBody:exit"() {
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classScopes.pop();
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},
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"FunctionDeclaration:exit": exitFunctionInFunctionMode,
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"FunctionExpression:exit": exitFunctionInFunctionMode,
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"ArrowFunctionExpression:exit": exitFunctionInFunctionMode
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});
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}
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return rule;
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}
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};
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