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/**
* @fileoverview Rule to warn when a function expression does not have a name.
* @author Kyle T. Nunery
*/
"use strict";
//------------------------------------------------------------------------------
// Requirements
//------------------------------------------------------------------------------
const astUtils = require("../ast-utils");
/**
* Checks whether or not a given variable is a function name.
* @param {eslint-scope.Variable} variable - A variable to check.
* @returns {boolean} `true` if the variable is a function name.
*/
function isFunctionName(variable) {
return variable && variable.defs[0].type === "FunctionName";
}
//------------------------------------------------------------------------------
// Rule Definition
//------------------------------------------------------------------------------
module.exports = {
meta: {
docs: {
description: "require or disallow named `function` expressions",
category: "Stylistic Issues",
recommended: false
},
schema: [
{
enum: ["always", "as-needed", "never"]
}
]
},
create(context) {
const never = context.options[0] === "never";
const asNeeded = context.options[0] === "as-needed";
/**
* Determines whether the current FunctionExpression node is a get, set, or
* shorthand method in an object literal or a class.
* @param {ASTNode} node - A node to check.
* @returns {boolean} True if the node is a get, set, or shorthand method.
*/
function isObjectOrClassMethod(node) {
const parent = node.parent;
return (parent.type === "MethodDefinition" || (
parent.type === "Property" && (
parent.method ||
parent.kind === "get" ||
parent.kind === "set"
)
));
}
/**
* Determines whether the current FunctionExpression node has a name that would be
* inferred from context in a conforming ES6 environment.
* @param {ASTNode} node - A node to check.
* @returns {boolean} True if the node would have a name assigned automatically.
*/
function hasInferredName(node) {
const parent = node.parent;
return isObjectOrClassMethod(node) ||
(parent.type === "VariableDeclarator" && parent.id.type === "Identifier" && parent.init === node) ||
(parent.type === "Property" && parent.value === node) ||
(parent.type === "AssignmentExpression" && parent.left.type === "Identifier" && parent.right === node) ||
(parent.type === "ExportDefaultDeclaration" && parent.declaration === node) ||
(parent.type === "AssignmentPattern" && parent.right === node);
}
return {
"FunctionExpression:exit"(node) {
// Skip recursive functions.
const nameVar = context.getDeclaredVariables(node)[0];
if (isFunctionName(nameVar) && nameVar.references.length > 0) {
return;
}
const hasName = Boolean(node.id && node.id.name);
const name = astUtils.getFunctionNameWithKind(node);
if (never) {
if (hasName) {
context.report({
node,
message: "Unexpected named {{name}}.",
data: { name }
});
}
} else {
if (!hasName && (asNeeded ? !hasInferredName(node) : !isObjectOrClassMethod(node))) {
context.report({
node,
message: "Unexpected unnamed {{name}}.",
data: { name }
});
}
}
}
};
}
};
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