Fixes encoding of circular referenced object / complex object

spec/common/providers/https.spec.ts

@@ -869,6 +869,21 @@ describe("encoding/decoding", () => {
     });
   });
 
+  it("Throws object with self reference", () => {
+    class TestClass {
+      foo: string;
+      bar: number;
+      self: TestClass;
+      constructor(foo: string, bar: number) {
+        this.foo = foo;
+        this.bar = bar;
+        this.self = this;
+      }
+    }
+    const testObject = new TestClass("hello", 1);
+    expect(()=>https.encode(testObject)).to.throw(`Data cannot be encoded in JSON: ${testObject}`);
+  });
+
   it("encodes function as an empty object", () => {
     expect(https.encode(() => "foo")).to.deep.equal({});
   });

src/common/providers/https.ts

@@ -395,12 +395,14 @@ const LONG_TYPE = "type.googleapis.com/google.protobuf.Int64Value";
 /** @hidden */
 const UNSIGNED_LONG_TYPE = "type.googleapis.com/google.protobuf.UInt64Value";
 
+/** @hidden */
+const SELF_REFERENCE_WEAKSET = new WeakSet<object|((...args:any[])=>any)>();
 /**
  * Encodes arbitrary data in our special format for JSON.
  * This is exposed only for testing.
  */
 /** @hidden */
-export function encode(data: any): any {
+export function encode(data: unknown): any {
   if (data === null || typeof data === "undefined") {
     return null;
   }
@@ -421,18 +423,36 @@ export function encode(data: any): any {
   if (Array.isArray(data)) {
     return data.map(encode);
   }
-  if (typeof data === "object" || typeof data === "function") {
-    // Sadly we don't have Object.fromEntries in Node 10, so we can't use a single
-    // list comprehension
-    const obj: Record<string, any> = {};
-    for (const [k, v] of Object.entries(data)) {
-      obj[k] = encode(v);
-    }
-    return obj;
+  if(!isFunctionOrObject(data)||SELF_REFERENCE_WEAKSET.has(data)) {
+    logger.error("Data cannot be encoded in JSON.", data);
+    throw new Error(`Data cannot be encoded in JSON: ${data}`);
+  }
+
+  // Sadly we don't have Object.fromEntries in Node 10, so we can't use a single
+  // list comprehension
+  const obj: Record<string, any> = {};
+
+  SELF_REFERENCE_WEAKSET.add(data);
+
+  for (const [k, v] of Object.entries(data)) {
+    obj[k] = encode(v);
   }
-  // If we got this far, the data is not encodable.
-  logger.error("Data cannot be encoded in JSON.", data);
-  throw new Error(`Data cannot be encoded in JSON: ${data}`);
+
+  // clean after recursive call -
+  // we don't want to keep references to objects that are not part of the current object
+  SELF_REFERENCE_WEAKSET.delete(data);
+
+  return obj;
+}
+
+function isFunctionOrObject(data: unknown): data is object|((...args:any[])=>any) {
+  const isObjectOrFunction = typeof data === "object" || typeof data === "function";
+
+  if (!isObjectOrFunction) {
+    // If we got this far, the data is not encodable.
+    return false;
+  }
+  return true;
 }
 
 /**