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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 }
+ });
+ }
+ }
+ }
+ };
+ }
+};