resolve sebastian comments

Author: Brian Chen

packages/firestore/src/lite-api/types.ts

@@ -34,7 +34,7 @@ export type Primitive = string | number | boolean | undefined | null;
 export type NestedUpdateFields<T extends Record<string, unknown>> =
   UnionToIntersection<
     {
-      [K in keyof T & string]: ChildUpdateFields<T[K], K>;
+      [K in keyof T & string]: ChildUpdateFields<K, T[K]>;
     }[keyof T & string] // Also include the generated prefix-string keys.
   >;
 
@@ -43,17 +43,17 @@ export type NestedUpdateFields<T extends Record<string, unknown>> =
  * to distribute union types such as `undefined | {...}` (happens for optional
  * props) or `{a: A} | {b: B}`.
  *
- * In this use case, `T1` is used to distribute the union types of `T[K]` on
+ * In this use case, `V` is used to distribute the union types of `T[K]` on
  * `Record`, since `T[K]` is evaluated as an expression and not distributed.
  *
  * See https://www.typescriptlang.org/docs/handbook/advanced-types.html#distributive-conditional-types
  */
-export type ChildUpdateFields<T1, K extends string> =
+export type ChildUpdateFields<K extends string, V> =
   // Only allow nesting for map values
-  T1 extends Record<string, unknown>
+  V extends Record<string, unknown>
     ? // Recurse into the map and add the prefix in front of each key
       // (e.g. Prefix 'bar.' to create: 'bar.baz' and 'bar.qux'.
-      AddPrefixToKeys<K, UpdateData<T1>>
+      AddPrefixToKeys<K, UpdateData<V>>
     : // UpdateData is always a map of values.
       never;
 

packages/firestore/test/lite/integration.test.ts

@@ -1585,6 +1585,42 @@ describe('withConverter() support', () => {
         });
       });
 
+      it('supports null fields', () => {
+        interface TestObjectOptional {
+          optionalStr?: string;
+          nested?: {
+            strOrNull: string | null;
+          };
+        }
+
+        const testConverterOptional = {
+          toFirestore(testObj: WithFieldValue<TestObjectOptional>) {
+            return { ...testObj };
+          },
+          fromFirestore(snapshot: QueryDocumentSnapshot): TestObjectOptional {
+            const data = snapshot.data();
+            return {
+              optionalStr: data.optionalStr,
+              nested: data.nested
+            };
+          }
+        };
+
+        return withTestDocAndInitialData(initialData, async docRef => {
+          const testDocRef: DocumentReference<TestObjectOptional> =
+            docRef.withConverter(testConverterOptional);
+
+          await updateDoc(testDocRef, {
+            nested: {
+              strOrNull: null
+            }
+          });
+          await updateDoc(testDocRef, {
+            'nested.strOrNull': null
+          });
+        });
+      });
+
       it('supports union fields', () => {
         interface TestObjectUnion {
           optionalStr?: string;
@@ -1612,13 +1648,6 @@ describe('withConverter() support', () => {
           const testDocRef: DocumentReference<TestObjectUnion> =
             docRef.withConverter(testConverterUnion);
 
-          await updateDoc(testDocRef, {
-            optionalStr: 'foo'
-          });
-          await updateDoc(testDocRef, {
-            'optionalStr': 'foo'
-          });
-
           await updateDoc(testDocRef, {
             nested: {
               requiredStr: 'foo'
@@ -1641,6 +1670,10 @@ describe('withConverter() support', () => {
             // @ts-expect-error
             'nested.requiredNumber': 'foo'
           });
+          await updateDoc(testDocRef, {
+            // @ts-expect-error
+            'nested.requiredNumber': null
+          });
         });
       });