Allow nested metadata

Author: Gudahtt

src/BaseControllerV2.ts

@@ -27,9 +27,11 @@ type RecursivePartial<T> = {
     ? RecursivePartial<U>[]
     : T[P] extends Primitive
     ? T[P]
-    : RecursivePartial<T>;
+    : RecursivePartial<T[P]>;
 };
 
+type NotArrayLike<T> = T extends [] ? never : T;
+
 /**
  * An anonymizing function
  *
@@ -50,7 +52,7 @@ export type Anonymizer<T> = (value: T) => T extends Primitive ? T : RecursivePar
  * get an anonymized representation of the state.
  */
 export type StateMetadata<T> = {
-  [P in keyof T]: StatePropertyMetadata<T[P]>;
+  [P in keyof T]: T[P] extends Primitive ? StatePropertyMetadata<T[P]> : StateMetadata<T[P]> | StatePropertyMetadata<T[P]>;
 };
 
 /**
@@ -63,9 +65,9 @@ export type StateMetadata<T> = {
  *   identifiable), or is set to a function that returns an anonymized
  *   representation of this state.
  */
-export interface StatePropertyMetadata<P> {
+export interface StatePropertyMetadata<T> {
   persist: boolean;
-  anonymous: boolean | Anonymizer<P>;
+  anonymous: boolean | Anonymizer<T>;
 }
 
 /**
@@ -153,10 +155,26 @@ export class BaseController<S extends Record<string, any>> {
 }
 
 // This function acts as a type guard. Using a `typeof` conditional didn't seem to work.
-function isAnonymizingFunction<T>(x: boolean | Anonymizer<T>): x is Anonymizer<T> {
+function isAnonymizingFunction<T>(x: boolean | Anonymizer<T> | StateMetadata<T>): x is Anonymizer<T> {
   return typeof x === 'function';
 }
 
+function isStateMetadata<T>(x: StatePropertyMetadata<T> | StateMetadata<T>): x is StateMetadata<T> {
+  return Object.keys(x).sort() !== ['anonymous', 'persist'];
+}
+
+function isStatePropertyMetadata<T>(x: StatePropertyMetadata<T> | StateMetadata<T>): x is StatePropertyMetadata<T> {
+  return Object.keys(x).sort() === ['anonymous', 'persist'];
+}
+
+function isPrimitive(x: any): x is Primitive {
+  return ['boolean', 'string', 'number', 'null'].includes(typeof x);
+}
+
+function isNotArrayLike<T>(x: any): x is NotArrayLike<T> {
+  return !Array.isArray(x);
+}
+
 /**
  * Returns an anonymized representation of the controller state.
  *
@@ -174,11 +192,20 @@ export function getAnonymizedState<S extends Record<string, any>>(
 ): RecursivePartial<S> {
   return Object.keys(state).reduce((anonymizedState, _key) => {
     const key: keyof S = _key; // https://stackoverflow.com/questions/63893394/string-cannot-be-used-to-index-type-t
-    const metadataValue = metadata[key].anonymous;
-    if (isAnonymizingFunction(metadataValue)) {
-      anonymizedState[key] = metadataValue(state[key]);
-    } else if (metadataValue) {
-      anonymizedState[key] = state[key];
+    const propertyMetadata = metadata[key];
+    const propertyValue = state[key];
+    if (isStateMetadata(propertyMetadata)) {
+      if (isPrimitive(propertyValue) || !isNotArrayLike(propertyValue)) {
+        throw new Error('Invalid metadata');
+      }
+      anonymizedState[key] = getAnonymizedState(propertyValue, propertyMetadata);
+    } else if (isStatePropertyMetadata(propertyMetadata)) {
+      const metadataValue = propertyMetadata.anonymous;
+      if (isAnonymizingFunction(metadataValue)) {
+        anonymizedState[key] = metadataValue(state[key]);
+      } else if (metadataValue) {
+        anonymizedState[key] = state[key];
+      }
     }
     return anonymizedState;
   }, {} as RecursivePartial<S>);
@@ -191,12 +218,25 @@ export function getAnonymizedState<S extends Record<string, any>>(
  * @param metadata - The controller state metadata, which describes which pieces of state should be persisted
  * @returns The subset of controller state that should be persisted
  */
-export function getPersistentState<S extends Record<string, any>>(state: S, metadata: StateMetadata<S>): Partial<S> {
+export function getPersistentState<S extends Record<string, any>>(
+  state: S,
+  metadata: StateMetadata<S>,
+): RecursivePartial<S> {
   return Object.keys(state).reduce((persistedState, _key) => {
     const key: keyof S = _key; // https://stackoverflow.com/questions/63893394/string-cannot-be-used-to-index-type-t
-    if (metadata[key].persist) {
-      persistedState[key] = state[key];
+    const propertyMetadata = metadata[key];
+    const propertyValue = state[key];
+    if (isStateMetadata(propertyMetadata)) {
+      if (isPrimitive(propertyValue) || !isNotArrayLike(propertyValue)) {
+        throw new Error('Invalid metadata');
+      }
+      persistedState[key] = getPersistentState(propertyValue, propertyMetadata);
+    } else if (isStatePropertyMetadata(propertyMetadata)) {
+      if (metadata[key].persist) {
+        persistedState[key] = state[key];
+      }
     }
+
     return persistedState;
-  }, {} as Partial<S>);
+  }, {} as RecursivePartial<S>);
 }