From b8194f90e534fcff25fc35956df424aa464c9df6 Mon Sep 17 00:00:00 2001
From: Samuel Hellawell <sshellawell@gmail.com>
Date: Tue, 4 Apr 2023 04:14:21 +0100
Subject: [PATCH] Fix empty objects in credential throws error

Signed-off-by: Samuel Hellawell <sshellawell@gmail.com>
---
 package.json                                  |  2 +-
 src/anonymous-credentials/schema.ts           | 30 ++++++++++++-------
 src/anonymous-credentials/util.ts             |  4 ++-
 src/util.ts                                   |  7 ++++-
 .../anonymous-credentials/credential.spec.ts  | 13 ++++++++
 5 files changed, 42 insertions(+), 14 deletions(-)

diff --git a/package.json b/package.json
index d21bcbfa..774ac106 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@docknetwork/crypto-wasm-ts",
-  "version": "0.31.2",
+  "version": "0.31.3",
   "description": "Typescript abstractions over Dock's Rust crypto library's WASM wrapper",
   "homepage": "https://github.com/docknetwork/crypto-wasm-ts",
   "main": "lib/index.js",
diff --git a/src/anonymous-credentials/schema.ts b/src/anonymous-credentials/schema.ts
index cdbebe5f..7b675831 100644
--- a/src/anonymous-credentials/schema.ts
+++ b/src/anonymous-credentials/schema.ts
@@ -544,6 +544,7 @@ export class CredentialSchema extends Versioned {
 
   static validateGeneric(schema: object, ignoreKeys: Set<string> = new Set()) {
     const [names, values] = this.flattenSchemaObj(schema);
+
     for (let i = 0; i < names.length; i++) {
       if (ignoreKeys.has(names[i])) {
         continue;
@@ -644,16 +645,16 @@ export class CredentialSchema extends Versioned {
           properties: {
             id: {
               type: 'string'
-            },
-          },
+            }
+          }
         },
         proof: {
           type: 'object',
           properties: {
             type: {
               type: 'string'
-            },
-          },
+            }
+          }
         }
       }
     };
@@ -1101,13 +1102,20 @@ export class CredentialSchema extends Versioned {
         } else if (schemaProps[key]['type'] == 'object' && typ == 'object') {
           const schemaKeys = new Set([...Object.keys(schemaProps[key]['properties'])]);
           const valKeys = new Set([...Object.keys(value)]);
-          for (const vk of valKeys) {
-            CredentialSchema.generateFromCredential(value, schemaProps[key]['properties']);
-          }
-          // Delete extra keys not in cred
-          for (const sk of schemaKeys) {
-            if (value[sk] === undefined) {
-              delete schemaKeys[sk];
+
+          // If empty object, skip it here otherwise causes problems downstream
+          if (schemaKeys.size === 0) {
+            delete schemaProps[key];
+          } else {
+            for (const vk of valKeys) {
+              // TODO: why this loop? seems useless?
+              CredentialSchema.generateFromCredential(value, schemaProps[key]['properties']);
+            }
+            // Delete extra keys not in cred
+            for (const sk of schemaKeys) {
+              if (value[sk] === undefined) {
+                delete schemaKeys[sk];
+              }
             }
           }
         } else {
diff --git a/src/anonymous-credentials/util.ts b/src/anonymous-credentials/util.ts
index a4ae2b27..1d3c1e48 100644
--- a/src/anonymous-credentials/util.ts
+++ b/src/anonymous-credentials/util.ts
@@ -32,6 +32,7 @@ import { ValueType, ValueTypes } from './schema';
 import { Encoder } from '../bbs-plus';
 import { SetupParam, Statement, WitnessEqualityMetaStatement } from '../composite-proof';
 import { SetupParamsTracker } from './setup-params-tracker';
+import { isEmptyObject } from '../util';
 
 export function dockAccumulatorParams(): AccumulatorParams {
   return Accumulator.generateParams(ACCUMULATOR_PARAMS_LABEL_BYTES);
@@ -56,7 +57,8 @@ export function dockSaverEncryptionGensUncompressed(): SaverEncryptionGensUncomp
 export function flattenTill2ndLastKey(obj: object): [string[], object[]] {
   const flattened = {};
   const temp = flatten(obj) as object;
-  for (const k of Object.keys(temp)) {
+  const tempKeys = Object.keys(temp).filter((key) => typeof temp[key] !== 'object' || !isEmptyObject(temp[key]));
+  for (const k of tempKeys) {
     // taken from https://stackoverflow.com/a/5555607
     const pos = k.lastIndexOf('.');
     const name = k.substring(0, pos);
diff --git a/src/util.ts b/src/util.ts
index 1a5d6c3f..474d2f5a 100644
--- a/src/util.ts
+++ b/src/util.ts
@@ -69,7 +69,12 @@ export function randomFieldElement(seed?: Uint8Array): Uint8Array {
  */
 export function flattenObjectToKeyValuesList(obj: object, flattenOptions = undefined): [string[], unknown[]] {
   const flattened = flatten(obj, flattenOptions) as object;
-  const keys = Object.keys(flattened).sort();
+
+  // Sort and filter keys to remove empty objects
+  // this is done because schema generation removes empty objects + nothing to encode
+  const keys = Object.keys(flattened)
+    .sort()
+    .filter((k) => typeof flattened[k] !== 'object' || !isEmptyObject(flattened[k]));
   // @ts-ignore
   const values = keys.map((k) => flattened[k]);
   return [keys, values];
diff --git a/tests/anonymous-credentials/credential.spec.ts b/tests/anonymous-credentials/credential.spec.ts
index 5ee25394..4e763f79 100644
--- a/tests/anonymous-credentials/credential.spec.ts
+++ b/tests/anonymous-credentials/credential.spec.ts
@@ -871,4 +871,17 @@ describe('Credential signing and verification', () => {
       checkResult(recreatedCred.verify(pk));
     }
   });
+
+  it('for credential with auto-generated schema and empty objects', () => {
+    const builder = new CredentialBuilder();
+    builder.schema = new CredentialSchema(CredentialSchema.essential());
+    builder.subject = {
+      fname: 'John',
+      emptyObject: {},
+      lname: 'Smith',
+    };
+
+    const cred = builder.sign(sk, undefined, {requireSameFieldsAsSchema: false});
+    checkResult(cred.verify(pk));
+  });
 });