diff options
Diffstat (limited to 'tools/node_modules/eslint/lib/rules/no-useless-call.js')
-rw-r--r-- | tools/node_modules/eslint/lib/rules/no-useless-call.js | 80 |
1 files changed, 80 insertions, 0 deletions
diff --git a/tools/node_modules/eslint/lib/rules/no-useless-call.js b/tools/node_modules/eslint/lib/rules/no-useless-call.js new file mode 100644 index 0000000000..e4820ac248 --- /dev/null +++ b/tools/node_modules/eslint/lib/rules/no-useless-call.js @@ -0,0 +1,80 @@ +/** + * @fileoverview A rule to disallow unnecessary `.call()` and `.apply()`. + * @author Toru Nagashima + */ + +"use strict"; + +const astUtils = require("../ast-utils"); + +//------------------------------------------------------------------------------ +// Helpers +//------------------------------------------------------------------------------ + +/** + * Checks whether or not a node is a `.call()`/`.apply()`. + * @param {ASTNode} node - A CallExpression node to check. + * @returns {boolean} Whether or not the node is a `.call()`/`.apply()`. + */ +function isCallOrNonVariadicApply(node) { + return ( + node.callee.type === "MemberExpression" && + node.callee.property.type === "Identifier" && + node.callee.computed === false && + ( + (node.callee.property.name === "call" && node.arguments.length >= 1) || + (node.callee.property.name === "apply" && node.arguments.length === 2 && node.arguments[1].type === "ArrayExpression") + ) + ); +} + + +/** + * Checks whether or not `thisArg` is not changed by `.call()`/`.apply()`. + * @param {ASTNode|null} expectedThis - The node that is the owner of the applied function. + * @param {ASTNode} thisArg - The node that is given to the first argument of the `.call()`/`.apply()`. + * @param {SourceCode} sourceCode - The ESLint source code object. + * @returns {boolean} Whether or not `thisArg` is not changed by `.call()`/`.apply()`. + */ +function isValidThisArg(expectedThis, thisArg, sourceCode) { + if (!expectedThis) { + return astUtils.isNullOrUndefined(thisArg); + } + return astUtils.equalTokens(expectedThis, thisArg, sourceCode); +} + +//------------------------------------------------------------------------------ +// Rule Definition +//------------------------------------------------------------------------------ + +module.exports = { + meta: { + docs: { + description: "disallow unnecessary calls to `.call()` and `.apply()`", + category: "Best Practices", + recommended: false + }, + + schema: [] + }, + + create(context) { + const sourceCode = context.getSourceCode(); + + return { + CallExpression(node) { + if (!isCallOrNonVariadicApply(node)) { + return; + } + + const applied = node.callee.object; + const expectedThis = (applied.type === "MemberExpression") ? applied.object : null; + const thisArg = node.arguments[0]; + + if (isValidThisArg(expectedThis, thisArg, sourceCode)) { + context.report({ node, message: "unnecessary '.{{name}}()'.", data: { name: node.callee.property.name } }); + } + } + }; + } +}; |