More granular table traits

crates/codegen/src/rust.rs

@@ -183,13 +183,15 @@ pub struct {insert_callback_id}(__sdk::CallbackId);
             write!(
                 out,
                 "
-impl<'ctx> __sdk::EventTable for {table_handle}<'ctx> {{
+impl<'ctx> __sdk::TableLike for {table_handle}<'ctx> {{
     type Row = {row_type};
     type EventContext = super::EventContext;
 
     fn count(&self) -> u64 {{ self.imp.count() }}
     fn iter(&self) -> impl Iterator<Item = {row_type}> + '_ {{ self.imp.iter() }}
+}}
 
+impl<'ctx> __sdk::WithInsert for {table_handle}<'ctx> {{
     type InsertCallbackId = {insert_callback_id};
 
     fn on_insert(
@@ -203,6 +205,8 @@ impl<'ctx> __sdk::EventTable for {table_handle}<'ctx> {{
         self.imp.remove_on_insert(callback.0)
     }}
 }}
+
+impl<'ctx> __sdk::EventTable for {table_handle}<'ctx> {{}}
 "
             );
         } else {
@@ -213,13 +217,15 @@ impl<'ctx> __sdk::EventTable for {table_handle}<'ctx> {{
                 out,
                 "pub struct {delete_callback_id}(__sdk::CallbackId);
 
-impl<'ctx> __sdk::Table for {table_handle}<'ctx> {{
+impl<'ctx> __sdk::TableLike for {table_handle}<'ctx> {{
     type Row = {row_type};
     type EventContext = super::EventContext;
 
     fn count(&self) -> u64 {{ self.imp.count() }}
     fn iter(&self) -> impl Iterator<Item = {row_type}> + '_ {{ self.imp.iter() }}
+}}
 
+impl<'ctx> __sdk::WithInsert for {table_handle}<'ctx> {{
     type InsertCallbackId = {insert_callback_id};
 
     fn on_insert(
@@ -232,7 +238,9 @@ impl<'ctx> __sdk::Table for {table_handle}<'ctx> {{
     fn remove_on_insert(&self, callback: {insert_callback_id}) {{
         self.imp.remove_on_insert(callback.0)
     }}
+}}
 
+impl<'ctx> __sdk::WithDelete for {table_handle}<'ctx> {{
     type DeleteCallbackId = {delete_callback_id};
 
     fn on_delete(
@@ -246,6 +254,8 @@ impl<'ctx> __sdk::Table for {table_handle}<'ctx> {{
         self.imp.remove_on_delete(callback.0)
     }}
 }}
+
+impl<'ctx> __sdk::Table for {table_handle}<'ctx> {{}}
 "
             );
 
@@ -258,7 +268,7 @@ impl<'ctx> __sdk::Table for {table_handle}<'ctx> {{
                     "
 pub struct {update_callback_id}(__sdk::CallbackId);
 
-impl<'ctx> __sdk::TableWithPrimaryKey for {table_handle}<'ctx> {{
+impl<'ctx> __sdk::WithUpdate for {table_handle}<'ctx> {{
     type UpdateCallbackId = {update_callback_id};
 
     fn on_update(
@@ -272,6 +282,8 @@ impl<'ctx> __sdk::TableWithPrimaryKey for {table_handle}<'ctx> {{
         self.imp.remove_on_update(callback.0)
     }}
 }}
+
+impl<'ctx> __sdk::TableWithPrimaryKey for {table_handle}<'ctx> {{}}
 "
                 );
             }
@@ -1877,7 +1889,7 @@ impl<Ctx: __sdk::DbContext<
         out,
         "EventContext",
         Some("__sdk::Event<Reducer>"),
-        "[`__sdk::Table::on_insert`], [`__sdk::Table::on_delete`] and [`__sdk::TableWithPrimaryKey::on_update`] callbacks",
+        "[`__sdk::WithInsert::on_insert`], [`__sdk::WithDelete::on_delete`] and [`__sdk::WithUpdate::on_update`] callbacks",
         Some("[`__sdk::Event`]"),
     );
 

sdks/rust/src/lib.rs

@@ -29,7 +29,7 @@ pub use db_connection::DbConnectionBuilder;
 pub use db_context::DbContext;
 pub use error::{Error, Result};
 pub use event::{Event, ReducerEvent, Status};
-pub use table::{EventTable, Table, TableWithPrimaryKey};
+pub use table::{EventTable, Table, TableLike, TableWithPrimaryKey, WithDelete, WithInsert, WithUpdate};
 
 pub use spacetime_module::SubscriptionHandle;
 pub use spacetimedb_client_api_messages::websocket::v1::Compression;
@@ -62,7 +62,7 @@ pub mod __codegen {
     pub use crate::subscription::{OnEndedCallback, SubscriptionBuilder, SubscriptionHandleImpl};
     pub use crate::{
         ConnectionId, DbConnectionBuilder, DbContext, Event, EventTable, Identity, ReducerEvent, ScheduleAt, Table,
-        TableWithPrimaryKey, TimeDuration, Timestamp, Uuid,
+        TableLike, TableWithPrimaryKey, TimeDuration, Timestamp, Uuid, WithDelete, WithInsert, WithUpdate,
     };
 }
 

sdks/rust/src/table.rs

@@ -1,4 +1,5 @@
-//! The [`Table`] and [`TableWithPrimaryKey`] traits,
+//! The [`TableLike`], [`Table`], [`TableWithPrimaryKey`], and [`EventTable`] traits,
+//! together with the [`WithInsert`], [`WithDelete`], and [`WithUpdate`] capability traits,
 //! which allow certain simple queries of the client cache,
 //! and expose row callbacks which run when subscribed rows are inserted, deleted or updated.
 //!
@@ -7,12 +8,10 @@
 //! which mediate access to tables in the client cache.
 //! Obtain a table handle by calling a method on `ctx.db`, where `ctx` is a `DbConnection` or `EventContext`.
 
-/// Trait implemented by table handles, which mediate access to tables in the client cache.
+/// Common functionality shared by table-like handles.
 ///
 /// Obtain a table handle by calling a method on `ctx.db`, where `ctx` is a `DbConnection` or `EventContext`.
-///
-/// For persistent (non-event) tables only. See [`EventTable`] for transient event tables.
-pub trait Table {
+pub trait TableLike {
     /// The type of rows stored in this table.
     type Row: 'static;
 
@@ -24,20 +23,32 @@ pub trait Table {
 
     /// An iterator over all the subscribed rows in the client cache.
     fn iter(&self) -> impl Iterator<Item = Self::Row> + '_;
+}
 
+/// Capability trait for table-like handles which support insert callbacks.
+pub trait WithInsert: TableLike {
     type InsertCallbackId;
-    /// Register a callback to run whenever a subscribed row is inserted into the client cache.
+
+    /// Register a callback to run whenever a row is observed as inserted by this table handle.
+    ///
+    /// For persistent tables, this means a subscribed row is inserted into the client cache.
+    /// For event tables, this means an event row is delivered.
     ///
     /// The returned [`Self::InsertCallbackId`] can be passed to [`Self::remove_on_insert`]
     /// to cancel the callback.
     fn on_insert(
         &self,
         callback: impl FnMut(&Self::EventContext, &Self::Row) + Send + 'static,
     ) -> Self::InsertCallbackId;
+
     /// Cancel a callback previously registered by [`Self::on_insert`], causing it not to run in the future.
     fn remove_on_insert(&self, callback: Self::InsertCallbackId);
+}
 
+/// Capability trait for table-like handles which support delete callbacks.
+pub trait WithDelete: TableLike {
     type DeleteCallbackId;
+
     /// Register a callback to run whenever a subscribed row is deleted from the client cache.
     ///
     /// The returned [`Self::DeleteCallbackId`] can be passed to [`Self::remove_on_delete`]
@@ -46,22 +57,15 @@ pub trait Table {
         &self,
         callback: impl FnMut(&Self::EventContext, &Self::Row) + Send + 'static,
     ) -> Self::DeleteCallbackId;
+
     /// Cancel a callback previously registered by [`Self::on_delete`], causing it not to run in the future.
     fn remove_on_delete(&self, callback: Self::DeleteCallbackId);
 }
 
-/// Subtrait of [`Table`] implemented only by tables with a column designated as a primary key,
-/// which allows the SDK to identify updates.
-///
-/// SpacetimeDB does not have a special notion of updates as a primitive operation.
-/// Instead, an update is a delete followed by an insert
-/// of rows with the same primary key within the same transaction.
-/// This means that the module's calls to `ctx.db.some_table().unique_column().update(...)`
-/// may not result in an update event on the client if `unique_column` is not the primary key,
-/// and that clients may observe update events resulting from deletes and inserts by the module
-/// without going through such an `update` method.
-pub trait TableWithPrimaryKey: Table {
+/// Capability trait for table-like handles which support update callbacks.
+pub trait WithUpdate: TableLike {
     type UpdateCallbackId;
+
     /// Register a callback to run whenever a subscribed row is updated within a transaction,
     /// with an old version deleted and a new version inserted with the same primary key.
     ///
@@ -74,38 +78,34 @@ pub trait TableWithPrimaryKey: Table {
         &self,
         callback: impl FnMut(&Self::EventContext, &Self::Row, &Self::Row) + Send + 'static,
     ) -> Self::UpdateCallbackId;
+
     /// Cancel a callback previously registered by [`Self::on_update`], causing it not to run in the future.
     fn remove_on_update(&self, callback: Self::UpdateCallbackId);
 }
 
+/// Trait implemented by persistent table handles, which mediate access to tables in the client cache.
+///
+/// Obtain a table handle by calling a method on `ctx.db`, where `ctx` is a `DbConnection` or `EventContext`.
+///
+/// For persistent (non-event) tables only. See [`EventTable`] for transient event tables.
+pub trait Table: TableLike + WithInsert + WithDelete {}
+
+/// Subtrait of [`Table`] implemented only by tables with a column designated as a primary key,
+/// which allows the SDK to identify updates.
+///
+/// SpacetimeDB does not have a special notion of updates as a primitive operation.
+/// Instead, an update is a delete followed by an insert
+/// of rows with the same primary key within the same transaction.
+/// This means that the module's calls to `ctx.db.some_table().unique_column().update(...)`
+/// may not result in an update event on the client if `unique_column` is not the primary key,
+/// and that clients may observe update events resulting from deletes and inserts by the module
+/// without going through such an `update` method.
+pub trait TableWithPrimaryKey: Table + WithUpdate {}
+
 /// Trait for event tables, whose rows are transient and never persisted in the client cache.
 ///
 /// Event table rows are delivered as inserts but are not stored;
 /// only `on_insert` callbacks fire, and `count`/`iter` always reflect an empty table.
 ///
 /// Obtain a table handle by calling a method on `ctx.db`, where `ctx` is a `DbConnection` or `EventContext`.
-pub trait EventTable {
-    /// The type of rows in this table.
-    type Row: 'static;
-
-    /// The `EventContext` type generated for the module which defines this table.
-    type EventContext;
-
-    /// The number of subscribed rows in the client cache (always 0 for event tables).
-    fn count(&self) -> u64;
-
-    /// An iterator over all the subscribed rows in the client cache (always empty for event tables).
-    fn iter(&self) -> impl Iterator<Item = Self::Row> + '_;
-
-    type InsertCallbackId;
-    /// Register a callback to run whenever a row is inserted.
-    ///
-    /// The returned [`Self::InsertCallbackId`] can be passed to [`Self::remove_on_insert`]
-    /// to cancel the callback.
-    fn on_insert(
-        &self,
-        callback: impl FnMut(&Self::EventContext, &Self::Row) + Send + 'static,
-    ) -> Self::InsertCallbackId;
-    /// Cancel a callback previously registered by [`Self::on_insert`], causing it not to run in the future.
-    fn remove_on_insert(&self, callback: Self::InsertCallbackId);
-}
+pub trait EventTable: TableLike + WithInsert {}