2 * @fileoverview Rule to control usage of strict mode directives.
3 * @author Brandon Mills
8 //------------------------------------------------------------------------------
10 //------------------------------------------------------------------------------
12 const astUtils = require("./utils/ast-utils");
14 //------------------------------------------------------------------------------
16 //------------------------------------------------------------------------------
19 * Gets all of the Use Strict Directives in the Directive Prologue of a group of
21 * @param {ASTNode[]} statements Statements in the program or function body.
22 * @returns {ASTNode[]} All of the Use Strict Directives.
24 function getUseStrictDirectives(statements) {
25 const directives = [];
27 for (let i = 0; i < statements.length; i++) {
28 const statement = statements[i];
31 statement.type === "ExpressionStatement" &&
32 statement.expression.type === "Literal" &&
33 statement.expression.value === "use strict"
35 directives[i] = statement;
45 * Checks whether a given parameter is a simple parameter.
46 * @param {ASTNode} node A pattern node to check.
47 * @returns {boolean} `true` if the node is an Identifier node.
49 function isSimpleParameter(node) {
50 return node.type === "Identifier";
54 * Checks whether a given parameter list is a simple parameter list.
55 * @param {ASTNode[]} params A parameter list to check.
56 * @returns {boolean} `true` if the every parameter is an Identifier node.
58 function isSimpleParameterList(params) {
59 return params.every(isSimpleParameter);
62 //------------------------------------------------------------------------------
64 //------------------------------------------------------------------------------
71 description: "require or disallow strict mode directives",
72 category: "Strict Mode",
74 url: "https://eslint.org/docs/rules/strict"
79 enum: ["never", "global", "function", "safe"]
85 function: "Use the function form of 'use strict'.",
86 global: "Use the global form of 'use strict'.",
87 multiple: "Multiple 'use strict' directives.",
88 never: "Strict mode is not permitted.",
89 unnecessary: "Unnecessary 'use strict' directive.",
90 module: "'use strict' is unnecessary inside of modules.",
91 implied: "'use strict' is unnecessary when implied strict mode is enabled.",
92 unnecessaryInClasses: "'use strict' is unnecessary inside of classes.",
93 nonSimpleParameterList: "'use strict' directive inside a function with non-simple parameter list throws a syntax error since ES2016.",
94 wrap: "Wrap {{name}} in a function with 'use strict' directive."
100 const ecmaFeatures = context.parserOptions.ecmaFeatures || {},
103 let mode = context.options[0] || "safe";
105 if (ecmaFeatures.impliedStrict) {
107 } else if (mode === "safe") {
108 mode = ecmaFeatures.globalReturn ? "global" : "function";
112 * Determines whether a reported error should be fixed, depending on the error type.
113 * @param {string} errorType The type of error
114 * @returns {boolean} `true` if the reported error should be fixed
116 function shouldFix(errorType) {
117 return errorType === "multiple" || errorType === "unnecessary" || errorType === "module" || errorType === "implied" || errorType === "unnecessaryInClasses";
121 * Gets a fixer function to remove a given 'use strict' directive.
122 * @param {ASTNode} node The directive that should be removed
123 * @returns {Function} A fixer function
125 function getFixFunction(node) {
126 return fixer => fixer.remove(node);
130 * Report a slice of an array of nodes with a given message.
131 * @param {ASTNode[]} nodes Nodes.
132 * @param {string} start Index to start from.
133 * @param {string} end Index to end before.
134 * @param {string} messageId Message to display.
135 * @param {boolean} fix `true` if the directive should be fixed (i.e. removed)
138 function reportSlice(nodes, start, end, messageId, fix) {
139 nodes.slice(start, end).forEach(node => {
140 context.report({ node, messageId, fix: fix ? getFixFunction(node) : null });
145 * Report all nodes in an array with a given message.
146 * @param {ASTNode[]} nodes Nodes.
147 * @param {string} messageId Message id to display.
148 * @param {boolean} fix `true` if the directive should be fixed (i.e. removed)
151 function reportAll(nodes, messageId, fix) {
152 reportSlice(nodes, 0, nodes.length, messageId, fix);
156 * Report all nodes in an array, except the first, with a given message.
157 * @param {ASTNode[]} nodes Nodes.
158 * @param {string} messageId Message id to display.
159 * @param {boolean} fix `true` if the directive should be fixed (i.e. removed)
162 function reportAllExceptFirst(nodes, messageId, fix) {
163 reportSlice(nodes, 1, nodes.length, messageId, fix);
167 * Entering a function in 'function' mode pushes a new nested scope onto the
168 * stack. The new scope is true if the nested function is strict mode code.
169 * @param {ASTNode} node The function declaration or expression.
170 * @param {ASTNode[]} useStrictDirectives The Use Strict Directives of the node.
173 function enterFunctionInFunctionMode(node, useStrictDirectives) {
174 const isInClass = classScopes.length > 0,
175 isParentGlobal = scopes.length === 0 && classScopes.length === 0,
176 isParentStrict = scopes.length > 0 && scopes[scopes.length - 1],
177 isStrict = useStrictDirectives.length > 0;
180 if (!isSimpleParameterList(node.params)) {
181 context.report({ node: useStrictDirectives[0], messageId: "nonSimpleParameterList" });
182 } else if (isParentStrict) {
183 context.report({ node: useStrictDirectives[0], messageId: "unnecessary", fix: getFixFunction(useStrictDirectives[0]) });
184 } else if (isInClass) {
185 context.report({ node: useStrictDirectives[0], messageId: "unnecessaryInClasses", fix: getFixFunction(useStrictDirectives[0]) });
188 reportAllExceptFirst(useStrictDirectives, "multiple", true);
189 } else if (isParentGlobal) {
190 if (isSimpleParameterList(node.params)) {
191 context.report({ node, messageId: "function" });
196 data: { name: astUtils.getFunctionNameWithKind(node) }
201 scopes.push(isParentStrict || isStrict);
205 * Exiting a function in 'function' mode pops its scope off the stack.
208 function exitFunctionInFunctionMode() {
213 * Enter a function and either:
214 * - Push a new nested scope onto the stack (in 'function' mode).
215 * - Report all the Use Strict Directives (in the other modes).
216 * @param {ASTNode} node The function declaration or expression.
219 function enterFunction(node) {
220 const isBlock = node.body.type === "BlockStatement",
221 useStrictDirectives = isBlock
222 ? getUseStrictDirectives(node.body.body) : [];
224 if (mode === "function") {
225 enterFunctionInFunctionMode(node, useStrictDirectives);
226 } else if (useStrictDirectives.length > 0) {
227 if (isSimpleParameterList(node.params)) {
228 reportAll(useStrictDirectives, mode, shouldFix(mode));
230 context.report({ node: useStrictDirectives[0], messageId: "nonSimpleParameterList" });
231 reportAllExceptFirst(useStrictDirectives, "multiple", true);
238 const useStrictDirectives = getUseStrictDirectives(node.body);
240 if (node.sourceType === "module") {
244 if (mode === "global") {
245 if (node.body.length > 0 && useStrictDirectives.length === 0) {
246 context.report({ node, messageId: "global" });
248 reportAllExceptFirst(useStrictDirectives, "multiple", true);
250 reportAll(useStrictDirectives, mode, shouldFix(mode));
253 FunctionDeclaration: enterFunction,
254 FunctionExpression: enterFunction,
255 ArrowFunctionExpression: enterFunction
258 if (mode === "function") {
259 Object.assign(rule, {
261 // Inside of class bodies are always strict mode.
263 classScopes.push(true);
269 "FunctionDeclaration:exit": exitFunctionInFunctionMode,
270 "FunctionExpression:exit": exitFunctionInFunctionMode,
271 "ArrowFunctionExpression:exit": exitFunctionInFunctionMode