refactor(datastore): storage adapters

[iartemiev]

Description of changes

Adds an abstract base class - StorageAdapterBase that encapsulates common storage adapter business logic.
Individual storage adapters, e.g. IndexedDBStorageAdapter extend the base class and only implement platform-specific business logic

This PR migrates IndexedDB and AsyncStorage to this pattern. I would like to get a sanity check from the team on the soundness of this approach before migrating the remaining 2 adapters (SQLite and Expo SQLite)

Description of how you validated changes

• unit tests
• manual testing

Checklist

• PR description included
• yarn test passes
• Tests are changed or added
• Relevant documentation is changed or added (and PR referenced)

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.

[codecov-commenter]

Codecov Report

Merging #11073 (8fcc68e) into main (b7f35a4) will decrease coverage by 0.08%.
The diff coverage is n/a.

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@@            Coverage Diff             @@
##             main   #11073      +/-   ##
==========================================
- Coverage   82.24%   82.16%   -0.08%     
==========================================
  Files         193      194       +1     
  Lines       19367    19355      -12     
  Branches     4185     4204      +19     
==========================================
- Hits        15928    15903      -25     
- Misses       3151     3166      +15     
+ Partials      288      286       -2     

see 17 files with indirect coverage changes

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[dpilch]

The approach looks sound to me. IMO it is safe to move forward with the other adapters.

I think there are some other areas to be DRYer (although I'm not sure it is worth the effort).

index 121a2bc44..aa62b9cb6 100644
--- a/packages/datastore/src/storage/adapter/AsyncStorageAdapter.ts
+++ b/packages/datastore/src/storage/adapter/AsyncStorageAdapter.ts
@@ -46,11 +46,8 @@ export class AsyncStorageAdapter extends StorageAdapterBase {
                return db;
        }
 
-       async clear(): Promise<void> {
+       async _clear(): Promise<void> {
                await this.db.clear();
-
-               this.db = undefined!;
-               this.initPromise = undefined!;
        }
 
        async batchSave<T extends PersistentModel>(
diff --git a/packages/datastore/src/storage/adapter/IndexedDBAdapter.ts b/packages/datastore/src/storage/adapter/IndexedDBAdapter.ts
index 24cca6f33..c42be7117 100644
--- a/packages/datastore/src/storage/adapter/IndexedDBAdapter.ts
+++ b/packages/datastore/src/storage/adapter/IndexedDBAdapter.ts
@@ -198,14 +198,11 @@ class IndexedDBAdapter extends StorageAdapterBase {
                return <T>result;
        }
 
-       async clear(): Promise<void> {
+       async _clear(): Promise<void> {
                await this.checkPrivate();
 
                this.db?.close();
                await idb.deleteDB(this.dbName);
-
-               this.db = undefined!;
-               this.initPromise = undefined!;
        }
 
        async save<T extends PersistentModel>(
diff --git a/packages/datastore/src/storage/adapter/StorageAdapterBase.ts b/packages/datastore/src/storage/adapter/StorageAdapterBase.ts
index bdfa56aa1..88cb2badc 100644
--- a/packages/datastore/src/storage/adapter/StorageAdapterBase.ts
+++ b/packages/datastore/src/storage/adapter/StorageAdapterBase.ts
@@ -108,7 +108,14 @@ export abstract class StorageAdapterBase implements Adapter {
         * Not enough implementation similarities between the adapters
         * to consolidate in the base class
         */
-       public abstract clear(): Promise<void>;
+       public clear(): Promise<void> {
+               return this._clear().then(() => {
+                       this.db = undefined!;
+                       this.initPromise = undefined!;
+               });
+       }
+
+       protected abstract _clear(): Promise<void>;
 
        public abstract save<T extends PersistentModel>(
                model: T,

[svidgen]

Setting a good direction, IMO. As we discussed offline, I think there's more we can do moving some of the delete traversal up, etc.. But, a good direction! Thanks!