AutoInferredSchema class

[vkarpov15]

Summary

#14954 points out an unfortunate issue: with our current automatic schema inference, there's no good way for InferRawDocType to handle nested schemas. The core issue there is that we don't have access to the SchemaDefinition type in TypeScript generics. class Schema<DocType> has the constructor schema definition param typed as SchemaDefinition<SchemaDefinitionType<RawDocType>, RawDocType> | DocType, and that type isn't something that we can use to infer the raw doc type.

This PR adds a separate AutoInferredSchema class that takes the schema definition as the first generic param. There's a separate class for backwards compatibility, to avoid breaking code like new Schema<UserType>.

In the long term, I think AutoInferredSchema is a step in the right direction, because we want the exact schema definition so we can infer both the correct raw document type and the correct hydrated document type, rather than trying to infer the raw document type and hydrated document type from the "both but not quite" behavior of InferSchemaType<>.

One big outstanding question: changing RawDocType = any to RawDocType = InferRawDocType<SchemaDef> in the AutoInferredSchema generics causes the test for #14954 test to fail with the following error, which makes it seem like 2-level deep subdoc schemas are treated as POJOs somewhere. While tests pass with the current setup, this error makes me feel like I'm missing something, so I'll take a step back and come back to this issue later.

  ✖  70:5  Argument of type { email: string; docArr: { test: string; }[]; password: string; dateOfBirth: NativeDate; subdoc?: { childSchemas: DocumentArray<{ model?: unknown; schema?: { [x: string]: unknown; } | null | undefined; }>; ... 49 more ...; eventNames?: {} | ... 1 more ... | undefined; } | null | undefined; } is not assignable to parameter of type { email: string; password: string; dateOfBirth: Date; subdoc?: { name: string; l2?: { myProp: number; } | null | undefined; } | null | undefined; docArr: { test: string; }[]; }.
  Types of property subdoc are incompatible.
    Type { childSchemas: DocumentArray<{ model?: unknown; schema?: { [x: string]: unknown; } | null | undefined; }>; index?: {} | null | undefined; set?: {} | null | undefined; once?: {} | null | undefined; ... 46 more ...; eventNames?: {} | ... 1 more ... | undefined; } | null | undefined is not assignable to type { name: string; l2?: { myProp: number; } | null | undefined; } | null | undefined.
      Property name is missing in type { childSchemas: DocumentArray<{ model?: unknown; schema?: { [x: string]: unknown; } | null | undefined; }>; index?: {} | null | undefined; set?: {} | null | undefined; once?: {} | null | undefined; ... 46 more ...; eventNames?: {} | ... 1 more ... | undefined; } but required in type { name: string; l2?: { myProp: number; } | null | undefined; }.  

  1 error

Examples

[hasezoey]

I have also tried to find where the error comes from, but i also have not found it.

While trying to find where the problem was, i wanted to get the generics for type debugging, but i found that using ObtainSchemaGeneric<> on a AutoInferredSchema somehow only returns unknown for EnforcedDocType and TSchemaOptions, all other properties (like M, DocType, TInstanceMethods) return the correct position, i could fix this specific issue with the following patch:

diff --git a/types/inferschematype.d.ts b/types/inferschematype.d.ts
index 07ee5087b..58b14977d 100644
--- a/types/inferschematype.d.ts
+++ b/types/inferschematype.d.ts
@@ -57,18 +57,29 @@ declare module 'mongoose' {
    * @param {alias} alias Targeted generic alias.
    */
   type ObtainSchemaGeneric<TSchema, alias extends 'EnforcedDocType' | 'M' | 'TInstanceMethods' | 'TQueryHelpers' | 'TVirtuals' | 'TStaticMethods' | 'TSchemaOptions' | 'DocType'> =
-   TSchema extends Schema<infer EnforcedDocType, infer M, infer TInstanceMethods, infer TQueryHelpers, infer TVirtuals, infer TStaticMethods, infer TSchemaOptions, infer DocType>
-     ? {
-       EnforcedDocType: EnforcedDocType;
-       M: M;
-       TInstanceMethods: TInstanceMethods;
-       TQueryHelpers: TQueryHelpers;
-       TVirtuals: TVirtuals;
-       TStaticMethods: TStaticMethods;
-       TSchemaOptions: TSchemaOptions;
-       DocType: DocType;
-     }[alias]
-     : unknown;
+    TSchema extends AutoInferredSchema<infer SchemaDef, infer EnforcedDocType, infer M, infer TInstanceMethods, infer TQueryHelpers, infer TVirtuals, infer TStaticMethods, infer TSchemaOptions, infer DocType> ?
+      {
+        EnforcedDocType: EnforcedDocType;
+        M: M;
+        TInstanceMethods: TInstanceMethods;
+        TQueryHelpers: TQueryHelpers;
+        TVirtuals: TVirtuals;
+        TStaticMethods: TStaticMethods;
+        TSchemaOptions: TSchemaOptions;
+        DocType: DocType;
+      }[alias]
+    : TSchema extends Schema<infer EnforcedDocType, infer M, infer TInstanceMethods, infer TQueryHelpers, infer TVirtuals, infer TStaticMethods, infer TSchemaOptions, infer DocType>
+      ? {
+        EnforcedDocType: EnforcedDocType;
+        M: M;
+        TInstanceMethods: TInstanceMethods;
+        TQueryHelpers: TQueryHelpers;
+        TVirtuals: TVirtuals;
+        TStaticMethods: TStaticMethods;
+        TSchemaOptions: TSchemaOptions;
+        DocType: DocType;
+      }[alias]
+      : unknown;
 
   type ResolveSchemaOptions<T> = MergeType<DefaultSchemaOptions, T>;

(adding a special case for AutoInferredSchema)

[hasezoey]

shouldnt it import it relatively?