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app_vue/node_modules/eslint/lib/rules/no-shadow.js

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+/**
+ * @fileoverview Rule to flag on declaring variables already declared in the outer scope
+ * @author Ilya Volodin
+ */
+
+"use strict";
+
+//------------------------------------------------------------------------------
+// Requirements
+//------------------------------------------------------------------------------
+
+const astUtils = require("./utils/ast-utils");
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+module.exports = {
+    meta: {
+        type: "suggestion",
+
+        docs: {
+            description: "disallow variable declarations from shadowing variables declared in the outer scope",
+            category: "Variables",
+            recommended: false,
+            url: "https://eslint.org/docs/rules/no-shadow"
+        },
+
+        schema: [
+            {
+                type: "object",
+                properties: {
+                    builtinGlobals: { type: "boolean", default: false },
+                    hoist: { enum: ["all", "functions", "never"], default: "functions" },
+                    allow: {
+                        type: "array",
+                        items: {
+                            type: "string"
+                        }
+                    }
+                },
+                additionalProperties: false
+            }
+        ],
+
+        messages: {
+            noShadow: "'{{name}}' is already declared in the upper scope on line {{shadowedLine}} column {{shadowedColumn}}.",
+            noShadowGlobal: "'{{name}}' is already a global variable."
+        }
+    },
+
+    create(context) {
+
+        const options = {
+            builtinGlobals: context.options[0] && context.options[0].builtinGlobals,
+            hoist: (context.options[0] && context.options[0].hoist) || "functions",
+            allow: (context.options[0] && context.options[0].allow) || []
+        };
+
+        /**
+         * Check if variable name is allowed.
+         * @param  {ASTNode} variable The variable to check.
+         * @returns {boolean} Whether or not the variable name is allowed.
+         */
+        function isAllowed(variable) {
+            return options.allow.indexOf(variable.name) !== -1;
+        }
+
+        /**
+         * Checks if a variable of the class name in the class scope of ClassDeclaration.
+         *
+         * ClassDeclaration creates two variables of its name into its outer scope and its class scope.
+         * So we should ignore the variable in the class scope.
+         * @param {Object} variable The variable to check.
+         * @returns {boolean} Whether or not the variable of the class name in the class scope of ClassDeclaration.
+         */
+        function isDuplicatedClassNameVariable(variable) {
+            const block = variable.scope.block;
+
+            return block.type === "ClassDeclaration" && block.id === variable.identifiers[0];
+        }
+
+        /**
+         * Checks if a variable is inside the initializer of scopeVar.
+         *
+         * To avoid reporting at declarations such as `var a = function a() {};`.
+         * But it should report `var a = function(a) {};` or `var a = function() { function a() {} };`.
+         * @param {Object} variable The variable to check.
+         * @param {Object} scopeVar The scope variable to look for.
+         * @returns {boolean} Whether or not the variable is inside initializer of scopeVar.
+         */
+        function isOnInitializer(variable, scopeVar) {
+            const outerScope = scopeVar.scope;
+            const outerDef = scopeVar.defs[0];
+            const outer = outerDef && outerDef.parent && outerDef.parent.range;
+            const innerScope = variable.scope;
+            const innerDef = variable.defs[0];
+            const inner = innerDef && innerDef.name.range;
+
+            return (
+                outer &&
+                inner &&
+                outer[0] < inner[0] &&
+                inner[1] < outer[1] &&
+                ((innerDef.type === "FunctionName" && innerDef.node.type === "FunctionExpression") || innerDef.node.type === "ClassExpression") &&
+                outerScope === innerScope.upper
+            );
+        }
+
+        /**
+         * Get a range of a variable's identifier node.
+         * @param {Object} variable The variable to get.
+         * @returns {Array|undefined} The range of the variable's identifier node.
+         */
+        function getNameRange(variable) {
+            const def = variable.defs[0];
+
+            return def && def.name.range;
+        }
+
+        /**
+         * Get declared line and column of a variable.
+         * @param {eslint-scope.Variable} variable The variable to get.
+         * @returns {Object} The declared line and column of the variable.
+         */
+        function getDeclaredLocation(variable) {
+            const identifier = variable.identifiers[0];
+            let obj;
+
+            if (identifier) {
+                obj = {
+                    global: false,
+                    line: identifier.loc.start.line,
+                    column: identifier.loc.start.column + 1
+                };
+            } else {
+                obj = {
+                    global: true
+                };
+            }
+            return obj;
+        }
+
+        /**
+         * Checks if a variable is in TDZ of scopeVar.
+         * @param {Object} variable The variable to check.
+         * @param {Object} scopeVar The variable of TDZ.
+         * @returns {boolean} Whether or not the variable is in TDZ of scopeVar.
+         */
+        function isInTdz(variable, scopeVar) {
+            const outerDef = scopeVar.defs[0];
+            const inner = getNameRange(variable);
+            const outer = getNameRange(scopeVar);
+
+            return (
+                inner &&
+                outer &&
+                inner[1] < outer[0] &&
+
+                // Excepts FunctionDeclaration if is {"hoist":"function"}.
+                (options.hoist !== "functions" || !outerDef || outerDef.node.type !== "FunctionDeclaration")
+            );
+        }
+
+        /**
+         * Checks the current context for shadowed variables.
+         * @param {Scope} scope Fixme
+         * @returns {void}
+         */
+        function checkForShadows(scope) {
+            const variables = scope.variables;
+
+            for (let i = 0; i < variables.length; ++i) {
+                const variable = variables[i];
+
+                // Skips "arguments" or variables of a class name in the class scope of ClassDeclaration.
+                if (variable.identifiers.length === 0 ||
+                    isDuplicatedClassNameVariable(variable) ||
+                    isAllowed(variable)
+                ) {
+                    continue;
+                }
+
+                // Gets shadowed variable.
+                const shadowed = astUtils.getVariableByName(scope.upper, variable.name);
+
+                if (shadowed &&
+                    (shadowed.identifiers.length > 0 || (options.builtinGlobals && "writeable" in shadowed)) &&
+                    !isOnInitializer(variable, shadowed) &&
+                    !(options.hoist !== "all" && isInTdz(variable, shadowed))
+                ) {
+                    const location = getDeclaredLocation(shadowed);
+                    const messageId = location.global ? "noShadowGlobal" : "noShadow";
+                    const data = { name: variable.name };
+
+                    if (!location.global) {
+                        data.shadowedLine = location.line;
+                        data.shadowedColumn = location.column;
+                    }
+                    context.report({
+                        node: variable.identifiers[0],
+                        messageId,
+                        data
+                    });
+                }
+            }
+        }
+
+        return {
+            "Program:exit"() {
+                const globalScope = context.getScope();
+                const stack = globalScope.childScopes.slice();
+
+                while (stack.length) {
+                    const scope = stack.pop();
+
+                    stack.push(...scope.childScopes);
+                    checkForShadows(scope);
+                }
+            }
+        };
+
+    }
+};