.config/coc/extensions/node_modules/coc-prettier/node_modules/eslint/lib/rules/no-shadow.js

   1 /**
   2  * @fileoverview Rule to flag on declaring variables already declared in the outer scope
   3  * @author Ilya Volodin
   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 module.exports = {
  19     meta: {
  20         type: "suggestion",
  21
  22         docs: {
  23             description: "disallow variable declarations from shadowing variables declared in the outer scope",
  24             category: "Variables",
  25             recommended: false,
  26             url: "https://eslint.org/docs/rules/no-shadow"
  27         },
  28
  29         schema: [
  30             {
  31                 type: "object",
  32                 properties: {
  33                     builtinGlobals: { type: "boolean", default: false },
  34                     hoist: { enum: ["all", "functions", "never"], default: "functions" },
  35                     allow: {
  36                         type: "array",
  37                         items: {
  38                             type: "string"
  39                         }
  40                     }
  41                 },
  42                 additionalProperties: false
  43             }
  44         ],
  45
  46         messages: {
  47             noShadow: "'{{name}}' is already declared in the upper scope on line {{shadowedLine}} column {{shadowedColumn}}.",
  48             noShadowGlobal: "'{{name}}' is already a global variable."
  49         }
  50     },
  51
  52     create(context) {
  53
  54         const options = {
  55             builtinGlobals: context.options[0] && context.options[0].builtinGlobals,
  56             hoist: (context.options[0] && context.options[0].hoist) || "functions",
  57             allow: (context.options[0] && context.options[0].allow) || []
  58         };
  59
  60         /**
  61          * Check if variable name is allowed.
  62          * @param  {ASTNode} variable The variable to check.
  63          * @returns {boolean} Whether or not the variable name is allowed.
  64          */
  65         function isAllowed(variable) {
  66             return options.allow.indexOf(variable.name) !== -1;
  67         }
  68
  69         /**
  70          * Checks if a variable of the class name in the class scope of ClassDeclaration.
  71          *
  72          * ClassDeclaration creates two variables of its name into its outer scope and its class scope.
  73          * So we should ignore the variable in the class scope.
  74          * @param {Object} variable The variable to check.
  75          * @returns {boolean} Whether or not the variable of the class name in the class scope of ClassDeclaration.
  76          */
  77         function isDuplicatedClassNameVariable(variable) {
  78             const block = variable.scope.block;
  79
  80             return block.type === "ClassDeclaration" && block.id === variable.identifiers[0];
  81         }
  82
  83         /**
  84          * Checks if a variable is inside the initializer of scopeVar.
  85          *
  86          * To avoid reporting at declarations such as `var a = function a() {};`.
  87          * But it should report `var a = function(a) {};` or `var a = function() { function a() {} };`.
  88          * @param {Object} variable The variable to check.
  89          * @param {Object} scopeVar The scope variable to look for.
  90          * @returns {boolean} Whether or not the variable is inside initializer of scopeVar.
  91          */
  92         function isOnInitializer(variable, scopeVar) {
  93             const outerScope = scopeVar.scope;
  94             const outerDef = scopeVar.defs[0];
  95             const outer = outerDef && outerDef.parent && outerDef.parent.range;
  96             const innerScope = variable.scope;
  97             const innerDef = variable.defs[0];
  98             const inner = innerDef && innerDef.name.range;
  99
 100             return (
 101                 outer &&
 102                 inner &&
 103                 outer[0] < inner[0] &&
 104                 inner[1] < outer[1] &&
 105                 ((innerDef.type === "FunctionName" && innerDef.node.type === "FunctionExpression") || innerDef.node.type === "ClassExpression") &&
 106                 outerScope === innerScope.upper
 107             );
 108         }
 109
 110         /**
 111          * Get a range of a variable's identifier node.
 112          * @param {Object} variable The variable to get.
 113          * @returns {Array|undefined} The range of the variable's identifier node.
 114          */
 115         function getNameRange(variable) {
 116             const def = variable.defs[0];
 117
 118             return def && def.name.range;
 119         }
 120
 121         /**
 122          * Get declared line and column of a variable.
 123          * @param {eslint-scope.Variable} variable The variable to get.
 124          * @returns {Object} The declared line and column of the variable.
 125          */
 126         function getDeclaredLocation(variable) {
 127             const identifier = variable.identifiers[0];
 128             let obj;
 129
 130             if (identifier) {
 131                 obj = {
 132                     global: false,
 133                     line: identifier.loc.start.line,
 134                     column: identifier.loc.start.column + 1
 135                 };
 136             } else {
 137                 obj = {
 138                     global: true
 139                 };
 140             }
 141             return obj;
 142         }
 143
 144         /**
 145          * Checks if a variable is in TDZ of scopeVar.
 146          * @param {Object} variable The variable to check.
 147          * @param {Object} scopeVar The variable of TDZ.
 148          * @returns {boolean} Whether or not the variable is in TDZ of scopeVar.
 149          */
 150         function isInTdz(variable, scopeVar) {
 151             const outerDef = scopeVar.defs[0];
 152             const inner = getNameRange(variable);
 153             const outer = getNameRange(scopeVar);
 154
 155             return (
 156                 inner &&
 157                 outer &&
 158                 inner[1] < outer[0] &&
 159
 160                 // Excepts FunctionDeclaration if is {"hoist":"function"}.
 161                 (options.hoist !== "functions" || !outerDef || outerDef.node.type !== "FunctionDeclaration")
 162             );
 163         }
 164
 165         /**
 166          * Checks the current context for shadowed variables.
 167          * @param {Scope} scope Fixme
 168          * @returns {void}
 169          */
 170         function checkForShadows(scope) {
 171             const variables = scope.variables;
 172
 173             for (let i = 0; i < variables.length; ++i) {
 174                 const variable = variables[i];
 175
 176                 // Skips "arguments" or variables of a class name in the class scope of ClassDeclaration.
 177                 if (variable.identifiers.length === 0 ||
 178                     isDuplicatedClassNameVariable(variable) ||
 179                     isAllowed(variable)
 180                 ) {
 181                     continue;
 182                 }
 183
 184                 // Gets shadowed variable.
 185                 const shadowed = astUtils.getVariableByName(scope.upper, variable.name);
 186
 187                 if (shadowed &&
 188                     (shadowed.identifiers.length > 0 || (options.builtinGlobals && "writeable" in shadowed)) &&
 189                     !isOnInitializer(variable, shadowed) &&
 190                     !(options.hoist !== "all" && isInTdz(variable, shadowed))
 191                 ) {
 192                     const location = getDeclaredLocation(shadowed);
 193                     const messageId = location.global ? "noShadowGlobal" : "noShadow";
 194                     const data = { name: variable.name };
 195
 196                     if (!location.global) {
 197                         data.shadowedLine = location.line;
 198                         data.shadowedColumn = location.column;
 199                     }
 200                     context.report({
 201                         node: variable.identifiers[0],
 202                         messageId,
 203                         data
 204                     });
 205                 }
 206             }
 207         }
 208
 209         return {
 210             "Program:exit"() {
 211                 const globalScope = context.getScope();
 212                 const stack = globalScope.childScopes.slice();
 213
 214                 while (stack.length) {
 215                     const scope = stack.pop();
 216
 217                     stack.push(...scope.childScopes);
 218                     checkForShadows(scope);
 219                 }
 220             }
 221         };
 222
 223     }
 224 };