eslint/lib/rules/no-inner-declarations.js

   1 /**
   2  * @fileoverview Rule to enforce declarations in program or function body root.
   3  * @author Brandon Mills
   4  */
   5
   6 "use strict";
   7
   8 //------------------------------------------------------------------------------
   9 // Requirements
  10 //------------------------------------------------------------------------------
  11
  12 const astUtils = require("./utils/ast-utils");
  13
  14 //------------------------------------------------------------------------------
  15 // Rule Definition
  16 //------------------------------------------------------------------------------
  17
  18 const validParent = new Set(["Program", "StaticBlock", "ExportNamedDeclaration", "ExportDefaultDeclaration"]);
  19 const validBlockStatementParent = new Set(["FunctionDeclaration", "FunctionExpression", "ArrowFunctionExpression"]);
  20
  21 /**
  22  * Finds the nearest enclosing context where this rule allows declarations and returns its description.
  23  * @param {ASTNode} node Node to search from.
  24  * @returns {string} Description. One of "program", "function body", "class static block body".
  25  */
  26 function getAllowedBodyDescription(node) {
  27     let { parent } = node;
  28
  29     while (parent) {
  30
  31         if (parent.type === "StaticBlock") {
  32             return "class static block body";
  33         }
  34
  35         if (astUtils.isFunction(parent)) {
  36             return "function body";
  37         }
  38
  39         ({ parent } = parent);
  40     }
  41
  42     return "program";
  43 }
  44
  45 /** @type {import('../shared/types').Rule} */
  46 module.exports = {
  47     meta: {
  48         type: "problem",
  49
  50         docs: {
  51             description: "disallow variable or `function` declarations in nested blocks",
  52             recommended: true,
  53             url: "https://eslint.org/docs/rules/no-inner-declarations"
  54         },
  55
  56         schema: [
  57             {
  58                 enum: ["functions", "both"]
  59             }
  60         ],
  61
  62         messages: {
  63             moveDeclToRoot: "Move {{type}} declaration to {{body}} root."
  64         }
  65     },
  66
  67     create(context) {
  68
  69         /**
  70          * Ensure that a given node is at a program or function body's root.
  71          * @param {ASTNode} node Declaration node to check.
  72          * @returns {void}
  73          */
  74         function check(node) {
  75             const parent = node.parent;
  76
  77             if (
  78                 parent.type === "BlockStatement" && validBlockStatementParent.has(parent.parent.type)
  79             ) {
  80                 return;
  81             }
  82
  83             if (validParent.has(parent.type)) {
  84                 return;
  85             }
  86
  87             context.report({
  88                 node,
  89                 messageId: "moveDeclToRoot",
  90                 data: {
  91                     type: (node.type === "FunctionDeclaration" ? "function" : "variable"),
  92                     body: getAllowedBodyDescription(node)
  93                 }
  94             });
  95         }
  96
  97
  98         return {
  99
 100             FunctionDeclaration: check,
 101             VariableDeclaration(node) {
 102                 if (context.options[0] === "both" && node.kind === "var") {
 103                     check(node);
 104                 }
 105             }
 106
 107         };
 108
 109     }
 110 };