Write custom serializer for bools in indexeddb

crates/matrix-sdk-indexeddb/src/crypto_store/mod.rs

@@ -374,7 +374,7 @@ impl IndexeddbCryptoStore {
             // serialize and encrypt the data about the request
             request: self.serialize_value_as_bytes(gossip_request)?,
 
-            unsent: if gossip_request.sent_out { None } else { Some(1) },
+            unsent: !gossip_request.sent_out,
         };
 
         Ok(obj.try_into()?)
@@ -1209,19 +1209,18 @@ struct GossipRequestIndexedDbObject {
 
     /// Whether the request has yet to be sent out.
     ///
-    /// Really, this represents a boolean value, but booleans don't work as keys
-    /// in indexeddb (see [ECMA spec]). In any case, we don't need to be
-    /// able to retrieve entries where `unsent` is false, so we may as well
-    /// omit them from the index (see also [Stack Overflow]).
+    /// Since we only need to be able to find requests where this is `true`, we
+    /// skip serialization in cases where it is `false`. That has the effect
+    /// of omitting it from the indexeddb index.
     ///
-    /// To avoid too much `serde` magic, we use an `Option`, and omit the value
-    /// altogether if it is `None`, which means it will be excluded from the
-    /// "unsent" index. If it is `Some`, the actual value is unimportant.
-    ///
-    /// [ECMA spec]: https://w3c.github.io/IndexedDB/#key
-    /// [Stack overflow]: https://stackoverflow.com/a/24501949/637864
-    #[serde(skip_serializing_if = "Option::is_none")]
-    unsent: Option<u8>,
+    /// We also use a custom serializer because bools can't be used as keys in
+    /// indexeddb.
+    #[serde(
+        default,
+        skip_serializing_if = "std::ops::Not::not",
+        with = "crate::serialize_bool_for_indexeddb"
+    )]
+    unsent: bool,
 }
 
 impl TryInto<JsValue> for GossipRequestIndexedDbObject {

crates/matrix-sdk-indexeddb/src/lib.rs

@@ -6,6 +6,8 @@ use thiserror::Error;
 #[cfg(feature = "e2e-encryption")]
 mod crypto_store;
 mod safe_encode;
+#[cfg(feature = "e2e-encryption")]
+mod serialize_bool_for_indexeddb;
 mod state_store;
 
 #[cfg(feature = "e2e-encryption")]

crates/matrix-sdk-indexeddb/src/serialize_bool_for_indexeddb.rs

@@ -0,0 +1,41 @@
+// Copyright 2023 The Matrix.org Foundation C.I.C.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+//! Booleans don't work as keys in indexeddb (see [ECMA spec]), so instead we
+//! serialize them as `0` or `1`.
+//!
+//! This module implements a custom serializer which can be used on `bool`
+//! struct fields with:
+//!
+//! ```ignore
+//! #[serde(with = "serialize_bool_for_indexeddb")]
+//! ```
+//!
+//! [ECMA spec]: https://w3c.github.io/IndexedDB/#key
+use serde::{Deserializer, Serializer};
+
+pub fn serialize<S>(v: &bool, s: S) -> Result<S::Ok, S::Error>
+where
+    S: Serializer,
+{
+    s.serialize_u8(if *v { 1 } else { 0 })
+}
+
+pub fn deserialize<'de, D>(d: D) -> Result<bool, D::Error>
+where
+    D: Deserializer<'de>,
+{
+    let v: u8 = serde::de::Deserialize::deserialize(d)?;
+    Ok(v != 0)
+}