feat: add AutoInferredSchema to work around schema inference issues in #14954

Author: vkarpov15

lib/mongoose.js

@@ -937,6 +937,15 @@ Mongoose.prototype.Mongoose = Mongoose;
 
 Mongoose.prototype.Schema = Schema;
 
+/**
+ * Identical to `Schema` at runtime. Exists purely to work around some TypeScript compatibility issues.
+ *
+ * @method AutoInferredSchema
+ * @api public
+ */
+
+Mongoose.prototype.AutoInferredSchema = Schema;
+
 /**
  * The Mongoose [SchemaType](https://mongoosejs.com/docs/api/schematype.html#SchemaType()) constructor
  *

test/types/inferrawdoctype.test.ts

@@ -1,4 +1,4 @@
-import { InferRawDocType } from 'mongoose';
+import { InferRawDocType, Schema, AutoInferredSchema } from 'mongoose';
 import { expectType, expectError } from 'tsd';
 
 function gh14839() {
@@ -17,9 +17,22 @@ function gh14839() {
     dateOfBirth: {
       type: Date,
       required: true
-    }
+    },
+    subdoc: new AutoInferredSchema({
+      name: { type: String, required: true },
+      l2: new AutoInferredSchema({
+        myProp: { type: Number, required: true }
+      })
+    }),
+    docArr: [new AutoInferredSchema({ test: { type: String, required: true } })]
   };
 
-  type UserType = InferRawDocType< typeof schemaDefinition>;
-  expectType<{ email: string, password: string, dateOfBirth: Date }>({} as UserType);
+  type UserType = InferRawDocType<typeof schemaDefinition>;
+  expectType<{
+    email: string,
+    password: string,
+    dateOfBirth: Date,
+    subdoc?: { name: string, l2?: { myProp: number } | null } | null,
+    docArr: { test: string }[]
+  }>({} as UserType);
 }

types/index.d.ts

@@ -252,6 +252,29 @@ declare module 'mongoose' {
     TVirtuals,
     TStaticMethods> = (schema: Schema<DocType, M, TInstanceMethods, TQueryHelpers, TVirtuals, TStaticMethods>, opts?: any) => void;
 
+  export class AutoInferredSchema<
+    SchemaDef = unknown,
+    RawDocType = any,
+    TModelType = Model<RawDocType, any, any, any>,
+    TInstanceMethods = {},
+    TQueryHelpers = {},
+    TVirtuals = {},
+    TStaticMethods = {},
+    TSchemaOptions = DefaultSchemaOptions,
+    DocType extends ApplySchemaOptions<
+      ObtainDocumentType<DocType, RawDocType, ResolveSchemaOptions<TSchemaOptions>>,
+      ResolveSchemaOptions<TSchemaOptions>
+    > = ApplySchemaOptions<
+      ObtainDocumentType<any, RawDocType, ResolveSchemaOptions<TSchemaOptions>>,
+      ResolveSchemaOptions<TSchemaOptions>
+    >,
+    THydratedDocumentType = HydratedDocument<FlatRecord<DocType>, TVirtuals & TInstanceMethods>
+  > extends Schema<RawDocType, TModelType, TInstanceMethods, TQueryHelpers, TVirtuals, TStaticMethods, TSchemaOptions, DocType, THydratedDocumentType> {
+    constructor(definition?: SchemaDef, options?: SchemaOptions<FlatRecord<DocType>, TInstanceMethods, TQueryHelpers, TStaticMethods, TVirtuals, THydratedDocumentType> | ResolveSchemaOptions<TSchemaOptions>);
+
+    _schemaDefinition: SchemaDef;
+  }
+
   export class Schema<
     RawDocType = any,
     TModelType = Model<RawDocType, any, any, any>,

types/inferrawdoctype.d.ts

@@ -6,6 +6,7 @@ import {
   PathWithTypePropertyBaseType,
   PathEnumOrString
 } from './inferschematype';
+import { InferSchemaType } from 'mongoose';
 
 declare module 'mongoose' {
   export type InferRawDocType<
@@ -35,6 +36,10 @@ declare module 'mongoose' {
     TypeKey
   >;
 
+  type InferRawDocTypeFromSchema<TSchema extends Schema> = TSchema extends AutoInferredSchema
+    ? InferRawDocType<TSchema['_schemaDefinition']>
+    : InferSchemaType<TSchema>;
+
   /**
    * Same as inferSchemaType, except:
    *
@@ -50,11 +55,11 @@ declare module 'mongoose' {
    */
   type ResolveRawPathType<PathValueType, Options extends SchemaTypeOptions<PathValueType> = {}, TypeKey extends string = DefaultSchemaOptions['typeKey']> =
   PathValueType extends Schema ?
-    InferSchemaType<PathValueType> :
+    InferRawDocTypeFromSchema<PathValueType> :
     PathValueType extends (infer Item)[] ?
       IfEquals<Item, never, any[], Item extends Schema ?
         // If Item is a schema, infer its type.
-        Array<InferSchemaType<Item>> :
+        Array<InferRawDocTypeFromSchema<Item>> :
         Item extends Record<TypeKey, any> ?
           Item[TypeKey] extends Function | String ?
             // If Item has a type key that's a string or a callable, it must be a scalar,
@@ -73,7 +78,7 @@ declare module 'mongoose' {
       >:
       PathValueType extends ReadonlyArray<infer Item> ?
         IfEquals<Item, never, any[], Item extends Schema ?
-          Array<InferSchemaType<Item>> :
+          Array<InferRawDocTypeFromSchema<Item>> :
           Item extends Record<TypeKey, any> ?
             Item[TypeKey] extends Function | String ?
               ObtainRawDocumentPathType<Item, TypeKey>[] :