Fix types on createReadOnly option of snapshotted views

spec/types.spec.ts

@@ -1,8 +1,19 @@
 /* eslint-disable @typescript-eslint/consistent-type-imports */
 import type { Has, IsExact } from "conditional-type-checks";
 import { assert } from "conditional-type-checks";
-import { SnapshotIn, TypesForModelPropsDeclaration, action, register } from "../src";
-import { IMaybeNullType, INodeModelType, IOptionalType, ISimpleType, types } from "../src";
+import {
+  ClassModel,
+  IMaybeNullType,
+  INodeModelType,
+  IOptionalType,
+  ISimpleType,
+  SnapshotIn,
+  TypesForModelPropsDeclaration,
+  action,
+  register,
+  snapshottedView,
+  types,
+} from "../src";
 import { NamedThingClass, TestClassModel } from "./fixtures/TestClassModel";
 import { NamedThing, TestModel } from "./fixtures/TestModel";
 
@@ -61,7 +72,7 @@ describe("SnapshotIn", () => {
           return "hello";
         }
         @action
-        mixinAction(value: string) {
+        mixinAction(_value: string) {
           // empty
         }
       }
@@ -77,4 +88,22 @@ describe("SnapshotIn", () => {
     assert<IsExact<Actual["optional"], string | undefined>>(true);
     assert<Has<keyof Actual, "mixinView">>(false);
   });
+
+  test("works on class models with snapshotted views", () => {
+    @register
+    class DataContainer extends ClassModel({ id: types.identifier }) {}
+
+    @register
+    class DataMap extends ClassModel({ stuff: types.map(DataContainer) }) {}
+
+    @register
+    class _SnapshottedViewClass extends TestClassModel {
+      @snapshottedView<typeof DataMap>({
+        createReadOnly: (value) => DataMap.createReadOnly(value),
+      })
+      get test() {
+        return DataMap.createReadOnly();
+      }
+    }
+  });
 });

src/class-model.ts

@@ -1,12 +1,14 @@
 import "reflect-metadata";
 
 import memoize from "lodash.memoize";
-import type { Instance, IModelType as MSTIModelType, ModelActions } from "mobx-state-tree";
+import { comparer, reaction, type IReactionDisposer } from "mobx";
+import type { IModelType as MSTIModelType, ModelActions } from "mobx-state-tree";
 import { types as mstTypes } from "mobx-state-tree";
 import { RegistrationError } from "./errors";
-import { InstantiatorBuilder } from "./fast-instantiator";
 import { FastGetBuilder } from "./fast-getter";
+import { InstantiatorBuilder } from "./fast-instantiator";
 import { defaultThrowAction, mstPropsFromQuickProps, propsFromModelPropsDeclaration } from "./model";
+import { getSnapshot } from "./snapshot";
 import {
   $context,
   $identifier,
@@ -26,13 +28,13 @@ import type {
   IAnyType,
   IClassModelType,
   IStateTreeNode,
+  Instance,
   ModelPropertiesDeclaration,
   ModelViews,
+  SnapshotIn,
   TypesForModelPropsDeclaration,
 } from "./types";
 import { cyrb53 } from "./utils";
-import { comparer, reaction, type IReactionDisposer } from "mobx";
-import { getSnapshot } from "./snapshot";
 
 /** @internal */
 type ActionMetadata = {
@@ -42,12 +44,12 @@ type ActionMetadata = {
 };
 
 /** Options that configure a snapshotted view */
-export interface SnapshottedViewOptions<V, T extends IAnyClassModelType> {
+export interface SnapshottedViewOptions<ViewReturnT, ParentNodeT extends IAnyClassModelType> {
   /** A function for converting a stored value in the snapshot back to the rich type for the view to return */
-  createReadOnly?: (value: V | undefined, node: Instance<T>) => V | undefined;
+  createReadOnly?: (value: SnapshotIn<ViewReturnT> | undefined, node: Instance<ParentNodeT>) => Instance<ViewReturnT> | undefined;
 
   /** A function for converting the view value to a snapshot value */
-  createSnapshot?: (value: V) => any;
+  createSnapshot?: (value: ViewReturnT) => any;
 
   /** A function that will be called when the view's reaction throws an error. */
   onError?: (error: any) => void;
@@ -74,6 +76,7 @@ export type VolatileMetadata = {
 };
 
 type VolatileInitializer<T> = (instance: T) => Record<string, any>;
+
 /** @internal */
 export type PropertyMetadata = ActionMetadata | ViewMetadata | SnapshottedViewMetadata | VolatileMetadata;