chore(wasm/keystore): add helper to open a migration connection/transaction

We cannot use the regular `Database::open()` because this would result
in infinite recursion when used in migrations.

Author: SimonThormeyer

keystore/src/connection/platform/wasm/migrations/migration_connection.rs

@@ -0,0 +1,56 @@
+use idb::builder::DatabaseBuilder;
+
+use crate::{
+    CryptoKeystoreError, CryptoKeystoreResult, Database, DatabaseKey,
+    connection::{
+        KeystoreDatabaseConnection, TransactionWrapper, platform::wasm::WasmStorageWrapper,
+        storage::WasmEncryptedStorage,
+    },
+};
+
+impl Database {
+    pub(crate) async fn migration_connection(
+        previous_builder: DatabaseBuilder,
+        key: &DatabaseKey,
+    ) -> CryptoKeystoreResult<KeystoreDatabaseConnection> {
+        let idb_during_migration = previous_builder.build().await?;
+        let wrapper_during_migration = WasmStorageWrapper::Persistent(idb_during_migration);
+        let storage_during_migration = WasmEncryptedStorage::new(key, wrapper_during_migration);
+        Ok(KeystoreDatabaseConnection::from_inner(storage_during_migration))
+    }
+
+    /// Open an idb store with a transaction during a migration, do some generic work on the transaction, commit the
+    /// transaction and close the store.
+    ///
+    /// Make sure you haven't got an open connection before calling this.
+    pub(crate) async fn migration_transaction<F>(
+        db_during_migration: KeystoreDatabaseConnection,
+        migration_work: F,
+    ) -> CryptoKeystoreResult<()>
+    where
+        F: AsyncFnOnce(&mut TransactionWrapper) -> CryptoKeystoreResult<()>,
+    {
+        let idb = match db_during_migration.storage().storage {
+            WasmStorageWrapper::Persistent(ref database) => database,
+            WasmStorageWrapper::InMemory(_) => {
+                return Err(CryptoKeystoreError::MigrationFailed(
+                    "In-memory keystore doesn't support migrations".into(),
+                ));
+            }
+        };
+        let stores = idb.store_names();
+        let mut conn = db_during_migration.conn().await;
+        let mut transaction = conn.new_transaction(&stores).await?;
+
+        migration_work(&mut transaction).await?;
+
+        let result = transaction.commit_tx().await;
+        db_during_migration.close().await?;
+        if result.is_err() {
+            return Err(CryptoKeystoreError::MigrationFailed(
+                "Migration transaction hasn't been cmmitted".into(),
+            ));
+        }
+        Ok(())
+    }
+}

keystore/src/connection/platform/wasm/migrations/mod.rs

@@ -1,5 +1,6 @@
 mod db_key_type_to_bytes;
 mod delete_credential_by_value;
+mod migration_connection;
 mod pre_v4;
 mod v0;
 mod v2;

keystore/src/connection/platform/wasm/mod.rs

@@ -54,6 +54,14 @@ impl WasmConnection {
 
         Ok(())
     }
+
+    /// Only for use during migrations.
+    pub(crate) fn from_inner(inner: WasmEncryptedStorage) -> Self {
+        Self {
+            name: None,
+            conn: inner,
+        }
+    }
 }
 
 impl DatabaseConnectionRequirements for WasmConnection {}