/** * @fileoverview Rule to check for implicit global variables, functions and classes. * @author Joshua Peek */ "use strict"; //------------------------------------------------------------------------------ // Rule Definition //------------------------------------------------------------------------------ /** @type {import('../types').Rule.RuleModule} */ module.exports = { meta: { type: "suggestion", defaultOptions: [ { lexicalBindings: false, }, ], docs: { description: "Disallow declarations in the global scope", recommended: false, url: "https://eslint.org/docs/latest/rules/no-implicit-globals", }, schema: [ { type: "object", properties: { lexicalBindings: { type: "boolean", }, }, additionalProperties: false, }, ], messages: { globalNonLexicalBinding: "Unexpected {{kind}} declaration in the global scope, wrap in an IIFE for a local variable, assign as global property for a global variable.", globalLexicalBinding: "Unexpected {{kind}} declaration in the global scope, wrap in a block or in an IIFE.", globalVariableLeak: "Global variable leak, declare the variable if it is intended to be local.", assignmentToReadonlyGlobal: "Unexpected assignment to read-only global variable.", redeclarationOfReadonlyGlobal: "Unexpected redeclaration of read-only global variable.", }, }, create(context) { const [{ lexicalBindings: checkLexicalBindings }] = context.options; const sourceCode = context.sourceCode; /** * Reports the node. * @param {ASTNode} node Node to report. * @param {string} messageId Id of the message to report. * @param {string|undefined} kind Declaration kind, can be 'var', 'const', 'let', function or class. * @returns {void} */ function report(node, messageId, kind) { context.report({ node, messageId, data: { kind, }, }); } return { Program(node) { const scope = sourceCode.getScope(node); scope.variables.forEach(variable => { // Only ESLint global variables have the `writable` key. const isReadonlyEslintGlobalVariable = variable.writeable === false; const isWritableEslintGlobalVariable = variable.writeable === true; if (isWritableEslintGlobalVariable) { // Everything is allowed with writable ESLint global variables. return; } // Variables exported by "exported" block comments if (variable.eslintExported) { return; } variable.defs.forEach(def => { const defNode = def.node; if ( def.type === "FunctionName" || (def.type === "Variable" && def.parent.kind === "var") ) { if (isReadonlyEslintGlobalVariable) { report( defNode, "redeclarationOfReadonlyGlobal", ); } else { report( defNode, "globalNonLexicalBinding", def.type === "FunctionName" ? "function" : `'${def.parent.kind}'`, ); } } if (checkLexicalBindings) { if ( def.type === "ClassName" || (def.type === "Variable" && (def.parent.kind === "let" || def.parent.kind === "const")) ) { if (isReadonlyEslintGlobalVariable) { report( defNode, "redeclarationOfReadonlyGlobal", ); } else { report( defNode, "globalLexicalBinding", def.type === "ClassName" ? "class" : `'${def.parent.kind}'`, ); } } } }); }); // Undeclared assigned variables. scope.implicit.variables.forEach(variable => { const scopeVariable = scope.set.get(variable.name); let messageId; if (scopeVariable) { // ESLint global variable if (scopeVariable.writeable) { return; } messageId = "assignmentToReadonlyGlobal"; } else { // Reference to an unknown variable, possible global leak. messageId = "globalVariableLeak"; } // def.node is an AssignmentExpression, ForInStatement or ForOfStatement. variable.defs.forEach(def => { report(def.node, messageId); }); }); }, }; }, };