--- /dev/null
+/**
+ * @fileoverview Enforce return after a callback.
+ * @author Jamund Ferguson
+ */
+"use strict";
+
+//------------------------------------------------------------------------------
+// Rule Definition
+//------------------------------------------------------------------------------
+
+module.exports = {
+ meta: {
+ type: "suggestion",
+
+ docs: {
+ description: "require `return` statements after callbacks",
+ category: "Node.js and CommonJS",
+ recommended: false,
+ url: "https://eslint.org/docs/rules/callback-return"
+ },
+
+ schema: [{
+ type: "array",
+ items: { type: "string" }
+ }],
+
+ messages: {
+ missingReturn: "Expected return with your callback function."
+ }
+ },
+
+ create(context) {
+
+ const callbacks = context.options[0] || ["callback", "cb", "next"],
+ sourceCode = context.getSourceCode();
+
+ //--------------------------------------------------------------------------
+ // Helpers
+ //--------------------------------------------------------------------------
+
+ /**
+ * Find the closest parent matching a list of types.
+ * @param {ASTNode} node The node whose parents we are searching
+ * @param {Array} types The node types to match
+ * @returns {ASTNode} The matched node or undefined.
+ */
+ function findClosestParentOfType(node, types) {
+ if (!node.parent) {
+ return null;
+ }
+ if (types.indexOf(node.parent.type) === -1) {
+ return findClosestParentOfType(node.parent, types);
+ }
+ return node.parent;
+ }
+
+ /**
+ * Check to see if a node contains only identifers
+ * @param {ASTNode} node The node to check
+ * @returns {boolean} Whether or not the node contains only identifers
+ */
+ function containsOnlyIdentifiers(node) {
+ if (node.type === "Identifier") {
+ return true;
+ }
+
+ if (node.type === "MemberExpression") {
+ if (node.object.type === "Identifier") {
+ return true;
+ }
+ if (node.object.type === "MemberExpression") {
+ return containsOnlyIdentifiers(node.object);
+ }
+ }
+
+ return false;
+ }
+
+ /**
+ * Check to see if a CallExpression is in our callback list.
+ * @param {ASTNode} node The node to check against our callback names list.
+ * @returns {boolean} Whether or not this function matches our callback name.
+ */
+ function isCallback(node) {
+ return containsOnlyIdentifiers(node.callee) && callbacks.indexOf(sourceCode.getText(node.callee)) > -1;
+ }
+
+ /**
+ * Determines whether or not the callback is part of a callback expression.
+ * @param {ASTNode} node The callback node
+ * @param {ASTNode} parentNode The expression node
+ * @returns {boolean} Whether or not this is part of a callback expression
+ */
+ function isCallbackExpression(node, parentNode) {
+
+ // ensure the parent node exists and is an expression
+ if (!parentNode || parentNode.type !== "ExpressionStatement") {
+ return false;
+ }
+
+ // cb()
+ if (parentNode.expression === node) {
+ return true;
+ }
+
+ // special case for cb && cb() and similar
+ if (parentNode.expression.type === "BinaryExpression" || parentNode.expression.type === "LogicalExpression") {
+ if (parentNode.expression.right === node) {
+ return true;
+ }
+ }
+
+ return false;
+ }
+
+ //--------------------------------------------------------------------------
+ // Public
+ //--------------------------------------------------------------------------
+
+ return {
+ CallExpression(node) {
+
+ // if we're not a callback we can return
+ if (!isCallback(node)) {
+ return;
+ }
+
+ // find the closest block, return or loop
+ const closestBlock = findClosestParentOfType(node, ["BlockStatement", "ReturnStatement", "ArrowFunctionExpression"]) || {};
+
+ // if our parent is a return we know we're ok
+ if (closestBlock.type === "ReturnStatement") {
+ return;
+ }
+
+ // arrow functions don't always have blocks and implicitly return
+ if (closestBlock.type === "ArrowFunctionExpression") {
+ return;
+ }
+
+ // block statements are part of functions and most if statements
+ if (closestBlock.type === "BlockStatement") {
+
+ // find the last item in the block
+ const lastItem = closestBlock.body[closestBlock.body.length - 1];
+
+ // if the callback is the last thing in a block that might be ok
+ if (isCallbackExpression(node, lastItem)) {
+
+ const parentType = closestBlock.parent.type;
+
+ // but only if the block is part of a function
+ if (parentType === "FunctionExpression" ||
+ parentType === "FunctionDeclaration" ||
+ parentType === "ArrowFunctionExpression"
+ ) {
+ return;
+ }
+
+ }
+
+ // ending a block with a return is also ok
+ if (lastItem.type === "ReturnStatement") {
+
+ // but only if the callback is immediately before
+ if (isCallbackExpression(node, closestBlock.body[closestBlock.body.length - 2])) {
+ return;
+ }
+ }
+
+ }
+
+ // as long as you're the child of a function at this point you should be asked to return
+ if (findClosestParentOfType(node, ["FunctionDeclaration", "FunctionExpression", "ArrowFunctionExpression"])) {
+ context.report({ node, messageId: "missingReturn" });
+ }
+
+ }
+
+ };
+ }
+};