fix(eslint-plugin): [explicit-module-boundary-types] cyclical referen…

…ce infinite recursion crash (#2482)

Co-authored-by: Tadhg McDonald-Jensen <tadhg.mcdonaldjensen@carleton.ca>

packages/eslint-plugin/src/rules/explicit-module-boundary-types.ts

@@ -96,6 +96,10 @@ export default util.createRule<Options, MessageIds>({
     // tracks functions that were found whilst traversing
     const foundFunctions: FunctionNode[] = [];
 
+    // all nodes visited, avoids infinite recursion for cyclic references
+    // (such as class member referring to itself)
+    const alreadyVisited = new Set<TSESTree.Node>();
+
     /*
     # How the rule works:
 
@@ -311,9 +315,10 @@ export default util.createRule<Options, MessageIds>({
     }
 
     function checkNode(node: TSESTree.Node | null): void {
-      if (node == null) {
+      if (node == null || alreadyVisited.has(node)) {
         return;
       }
+      alreadyVisited.add(node);
 
       switch (node.type) {
         case AST_NODE_TYPES.ArrowFunctionExpression:

packages/eslint-plugin/tests/rules/explicit-module-boundary-types.test.ts

@@ -654,6 +654,11 @@ export abstract class Foo<T> {
     `
 export declare class Foo {
   set time(seconds: number);
+}
+    `,
+    `
+export class A {
+  b = A;
 }
     `,
   ],