Fix

dev/src/collection-group.ts

@@ -146,7 +146,8 @@ export class CollectionGroup<
    * Applies a custom data converter to this `CollectionGroup`, allowing you
    * to use your own custom model objects with Firestore. When you call get()
    * on the returned `CollectionGroup`, the provided converter will convert
-   * between Firestore data and your custom type U.
+   * between Firestore data of type `NewDbModelType` and your custom type
+   * `NewAppModelType`.
    *
    * Using the converter allows you to specify generic type arguments when
    * storing and retrieving objects from Firestore.

dev/src/document.ts

@@ -151,13 +151,14 @@ export class DocumentSnapshot<
    * @param obj The object to store in the DocumentSnapshot.
    * @return The created DocumentSnapshot.
    */
-  static fromObject<U>(
-    ref: firestore.DocumentReference<U>,
-    obj: firestore.DocumentData
-  ): DocumentSnapshot<U> {
-    const serializer = (ref as DocumentReference<U>).firestore._serializer!;
+  static fromObject<AppModelType, DbModelType>(
+    ref: firestore.DocumentReference<AppModelType, DbModelType>,
+    obj: DbModelType
+  ): DocumentSnapshot<AppModelType, DbModelType> {
+    const serializer = (ref as DocumentReference<AppModelType, DbModelType>)
+      .firestore._serializer!;
     return new DocumentSnapshot(
-      ref as DocumentReference<U>,
+      ref as DocumentReference<AppModelType, DbModelType>,
       serializer.encodeFields(obj)
     );
   }
@@ -173,11 +174,12 @@ export class DocumentSnapshot<
    * @param data The field/value map to expand.
    * @return The created DocumentSnapshot.
    */
-  static fromUpdateMap<U>(
-    ref: firestore.DocumentReference<U>,
+  static fromUpdateMap<AppModelType, DbModelType>(
+    ref: firestore.DocumentReference<AppModelType, DbModelType>,
     data: UpdateMap
-  ): DocumentSnapshot<U> {
-    const serializer = (ref as DocumentReference<U>).firestore._serializer!;
+  ): DocumentSnapshot<AppModelType, DbModelType> {
+    const serializer = (ref as DocumentReference<AppModelType, DbModelType>)
+      .firestore._serializer!;
 
     /**
      * Merges 'value' at the field path specified by the path array into
@@ -247,7 +249,10 @@ export class DocumentSnapshot<
       merge(res, value, path, 0);
     }
 
-    return new DocumentSnapshot(ref as DocumentReference<U>, res);
+    return new DocumentSnapshot(
+      ref as DocumentReference<AppModelType, DbModelType>,
+      res
+    );
   }
 
   /**

dev/src/index.ts

@@ -172,7 +172,8 @@ const MAX_CONCURRENT_REQUESTS_PER_CLIENT = 100;
 
 /**
  * Converter used by [withConverter()]{@link Query#withConverter} to transform
- * user objects of type T into Firestore data.
+ * user objects of type `AppModelType` into Firestore data of type
+ * `DbModelType`.
  *
  * Using the converter allows you to specify generic type arguments when storing
  * and retrieving objects from Firestore.
@@ -212,10 +213,10 @@ const MAX_CONCURRENT_REQUESTS_PER_CLIENT = 100;
  *
  * ```
  * @property {Function} toFirestore Called by the Firestore SDK to convert a
- * custom model object of type T into a plain Javascript object (suitable for
- * writing directly to the Firestore database).
+ * custom model object of type `AppModelType` into a plain Javascript object
+ * (suitable for writing directly to the Firestore database).
  * @property {Function} fromFirestore Called by the Firestore SDK to convert
- * Firestore data into an object of type T.
+ * Firestore data into an object of type `AppModelType`.
  * @typedef {Object} FirestoreDataConverter
  */
 

dev/src/reference.ts

@@ -442,7 +442,8 @@ export class DocumentReference<
    * [SetOptions]{@link SetOptions}, the provided data can be merged into an
    * existing document.
    *
-   * @param {T|Partial<T>} data A map of the fields and values for the document.
+   * @param {T|Partial<AppModelType>} data A map of the fields and values for
+   * the document.
    * @param {SetOptions=} options An object to configure the set behavior.
    * @param {boolean=} options.merge If true, set() merges the values specified
    * in its data argument. Fields omitted from this set() call remain untouched.
@@ -630,7 +631,8 @@ export class DocumentReference<
    * Applies a custom data converter to this DocumentReference, allowing you to
    * use your own custom model objects with Firestore. When you call set(),
    * get(), etc. on the returned DocumentReference instance, the provided
-   * converter will convert between Firestore data and your custom type U.
+   * converter will convert between Firestore data of type `NewDbModelType` and
+   * your custom type `NewAppModelType`.
    *
    * Using the converter allows you to specify generic type arguments when
    * storing and retrieving objects from Firestore.
@@ -1678,9 +1680,7 @@ export class Query<
    * });
    * ```
    */
-  select(
-    ...fieldPaths: Array<string | FieldPath>
-  ): Query<firestore.DocumentData> {
+  select(...fieldPaths: Array<string | FieldPath>): Query {
     const fields: api.StructuredQuery.IFieldReference[] = [];
 
     if (fieldPaths.length === 0) {
@@ -2766,8 +2766,7 @@ export class Query<
    * Applies a custom data converter to this Query, allowing you to use your
    * own custom model objects with Firestore. When you call get() on the
    * returned Query, the provided converter will convert between Firestore
-   * data and your custom type of type `NewDbModelType` and your custom type
-   * `NewAppModelType`.
+   * data of type `NewDbModelType` and your custom type `NewAppModelType`.
    *
    * Using the converter allows you to specify generic type arguments when
    * storing and retrieving objects from Firestore.
@@ -3096,7 +3095,8 @@ export class CollectionReference<
    * Applies a custom data converter to this CollectionReference, allowing you
    * to use your own custom model objects with Firestore. When you call add() on
    * the returned CollectionReference instance, the provided converter will
-   * convert between Firestore data and your custom type U.
+   * convert between Firestore data of type `NewDbModelType` and your custom
+   * type `NewAppModelType`.
    *
    * Using the converter allows you to specify generic type arguments when
    * storing and retrieving objects from Firestore.

types/firestore.d.ts

@@ -1377,8 +1377,8 @@ declare namespace FirebaseFirestore {
      * Applies a custom data converter to this DocumentReference, allowing you
      * to use your own custom model objects with Firestore. When you call
      * set(), get(), etc. on the returned DocumentReference instance, the
-     * provided converter will convert between Firestore data and your custom
-     * type U.
+     * provided converter will convert between Firestore data of type
+     * `NewDbModelType` and your custom type `NewAppModelType`.
      *
      * @param converter Converts objects to and from Firestore. Passing in
      * `null` removes the current converter.
@@ -2042,7 +2042,8 @@ declare namespace FirebaseFirestore {
      * Applies a custom data converter to this `CollectionGroup`, allowing you
      * to use your own custom model objects with Firestore. When you call get()
      * on the returned `CollectionGroup`, the provided converter will convert
-     * between Firestore data and your custom type U.
+     * between Firestore data of type `NewDbModelType` and your custom type
+     * `NewAppModelType`.
      *
      * Using the converter allows you to specify generic type arguments when
      * storing and retrieving objects from Firestore.
@@ -2081,10 +2082,12 @@ declare namespace FirebaseFirestore {
      *
      * @param converter Converts objects to and from Firestore. Passing in
      * `null` removes the current converter.
-     * @return A `CollectionGroup<U>` that uses the provided converter.
+     * @return A `CollectionGroup` that uses the provided converter.
      */
-    withConverter<U>(converter: FirestoreDataConverter<U>): CollectionGroup<U>;
-    withConverter(converter: null): CollectionGroup<DocumentData>;
+    withConverter<AppModelType, DbModelType>(
+      converter: FirestoreDataConverter<AppModelType, DbModelType>
+    ): CollectionGroup<AppModelType, DbModelType>;
+    withConverter(converter: null): CollectionGroup;
   }
 
   /**