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Diffstat (limited to 'tools/node_modules/eslint/lib/rules/no-useless-constructor.js')
-rw-r--r-- | tools/node_modules/eslint/lib/rules/no-useless-constructor.js | 182 |
1 files changed, 182 insertions, 0 deletions
diff --git a/tools/node_modules/eslint/lib/rules/no-useless-constructor.js b/tools/node_modules/eslint/lib/rules/no-useless-constructor.js new file mode 100644 index 0000000000..f790c789f5 --- /dev/null +++ b/tools/node_modules/eslint/lib/rules/no-useless-constructor.js @@ -0,0 +1,182 @@ +/** + * @fileoverview Rule to flag the use of redundant constructors in classes. + * @author Alberto RodrÃguez + */ +"use strict"; + +//------------------------------------------------------------------------------ +// Helpers +//------------------------------------------------------------------------------ + +/** + * Checks whether a given array of statements is a single call of `super`. + * + * @param {ASTNode[]} body - An array of statements to check. + * @returns {boolean} `true` if the body is a single call of `super`. + */ +function isSingleSuperCall(body) { + return ( + body.length === 1 && + body[0].type === "ExpressionStatement" && + body[0].expression.type === "CallExpression" && + body[0].expression.callee.type === "Super" + ); +} + +/** + * Checks whether a given node is a pattern which doesn't have any side effects. + * Default parameters and Destructuring parameters can have side effects. + * + * @param {ASTNode} node - A pattern node. + * @returns {boolean} `true` if the node doesn't have any side effects. + */ +function isSimple(node) { + return node.type === "Identifier" || node.type === "RestElement"; +} + +/** + * Checks whether a given array of expressions is `...arguments` or not. + * `super(...arguments)` passes all arguments through. + * + * @param {ASTNode[]} superArgs - An array of expressions to check. + * @returns {boolean} `true` if the superArgs is `...arguments`. + */ +function isSpreadArguments(superArgs) { + return ( + superArgs.length === 1 && + superArgs[0].type === "SpreadElement" && + superArgs[0].argument.type === "Identifier" && + superArgs[0].argument.name === "arguments" + ); +} + +/** + * Checks whether given 2 nodes are identifiers which have the same name or not. + * + * @param {ASTNode} ctorParam - A node to check. + * @param {ASTNode} superArg - A node to check. + * @returns {boolean} `true` if the nodes are identifiers which have the same + * name. + */ +function isValidIdentifierPair(ctorParam, superArg) { + return ( + ctorParam.type === "Identifier" && + superArg.type === "Identifier" && + ctorParam.name === superArg.name + ); +} + +/** + * Checks whether given 2 nodes are a rest/spread pair which has the same values. + * + * @param {ASTNode} ctorParam - A node to check. + * @param {ASTNode} superArg - A node to check. + * @returns {boolean} `true` if the nodes are a rest/spread pair which has the + * same values. + */ +function isValidRestSpreadPair(ctorParam, superArg) { + return ( + ctorParam.type === "RestElement" && + superArg.type === "SpreadElement" && + isValidIdentifierPair(ctorParam.argument, superArg.argument) + ); +} + +/** + * Checks whether given 2 nodes have the same value or not. + * + * @param {ASTNode} ctorParam - A node to check. + * @param {ASTNode} superArg - A node to check. + * @returns {boolean} `true` if the nodes have the same value or not. + */ +function isValidPair(ctorParam, superArg) { + return ( + isValidIdentifierPair(ctorParam, superArg) || + isValidRestSpreadPair(ctorParam, superArg) + ); +} + +/** + * Checks whether the parameters of a constructor and the arguments of `super()` + * have the same values or not. + * + * @param {ASTNode} ctorParams - The parameters of a constructor to check. + * @param {ASTNode} superArgs - The arguments of `super()` to check. + * @returns {boolean} `true` if those have the same values. + */ +function isPassingThrough(ctorParams, superArgs) { + if (ctorParams.length !== superArgs.length) { + return false; + } + + for (let i = 0; i < ctorParams.length; ++i) { + if (!isValidPair(ctorParams[i], superArgs[i])) { + return false; + } + } + + return true; +} + +/** + * Checks whether the constructor body is a redundant super call. + * + * @param {Array} body - constructor body content. + * @param {Array} ctorParams - The params to check against super call. + * @returns {boolean} true if the construtor body is redundant + */ +function isRedundantSuperCall(body, ctorParams) { + return ( + isSingleSuperCall(body) && + ctorParams.every(isSimple) && + ( + isSpreadArguments(body[0].expression.arguments) || + isPassingThrough(ctorParams, body[0].expression.arguments) + ) + ); +} + +//------------------------------------------------------------------------------ +// Rule Definition +//------------------------------------------------------------------------------ + +module.exports = { + meta: { + docs: { + description: "disallow unnecessary constructors", + category: "ECMAScript 6", + recommended: false + }, + + schema: [] + }, + + create(context) { + + /** + * Checks whether a node is a redundant constructor + * @param {ASTNode} node - node to check + * @returns {void} + */ + function checkForConstructor(node) { + if (node.kind !== "constructor") { + return; + } + + const body = node.value.body.body; + const ctorParams = node.value.params; + const superClass = node.parent.parent.superClass; + + if (superClass ? isRedundantSuperCall(body, ctorParams) : (body.length === 0)) { + context.report({ + node, + message: "Useless constructor." + }); + } + } + + return { + MethodDefinition: checkForConstructor + }; + } +}; |