Preserve reducer order in schema conversion

crates/core/src/host/module_host.rs

@@ -238,14 +238,12 @@ impl ModuleInfo {
 }
 
 /// A bidirectional map between `Identifiers` (reducer names) and `ReducerId`s.
-/// Invariant: the reducer names are in alphabetical order.
+/// Invariant: the reducer names are in the same order as they were declared in the `ModuleDef`.
 pub struct ReducersMap(IndexSet<Box<str>>);
 
 impl<'a> FromIterator<&'a str> for ReducersMap {
     fn from_iter<T: IntoIterator<Item = &'a str>>(iter: T) -> Self {
-        let mut sorted = Vec::from_iter(iter);
-        sorted.sort();
-        ReducersMap(sorted.into_iter().map_into().collect())
+        Self(iter.into_iter().map_into().collect())
     }
 }
 

crates/schema/Cargo.toml

@@ -17,6 +17,7 @@ spacetimedb-data-structures.workspace = true
 spacetimedb-sql-parser.workspace = true
 
 anyhow.workspace = true
+indexmap.workspace = true
 itertools.workspace = true
 lazy_static.workspace = true
 thiserror.workspace = true

crates/schema/src/def.rs

@@ -24,6 +24,7 @@ use crate::schema::{Schema, TableSchema};
 use crate::type_for_generate::{AlgebraicTypeUse, ProductTypeDef, TypespaceForGenerate};
 use deserialize::ReducerArgsDeserializeSeed;
 use hashbrown::Equivalent;
+use indexmap::IndexMap;
 use itertools::Itertools;
 use spacetimedb_data_structures::error_stream::{CollectAllErrors, CombineErrors, ErrorStream};
 use spacetimedb_data_structures::map::HashMap;
@@ -84,7 +85,9 @@ pub struct ModuleDef {
     tables: IdentifierMap<TableDef>,
 
     /// The reducers of the module definition.
-    reducers: IdentifierMap<ReducerDef>,
+    /// Note: this is using IndexMap because reducer order is important
+    /// and must be preserved for future calls to `__call_reducer__`.
+    reducers: IndexMap<Identifier, ReducerDef>,
 
     /// The type definitions of the module definition.
     types: HashMap<ScopedTypeName, TypeDef>,
@@ -355,7 +358,7 @@ impl From<ModuleDef> for RawModuleDefV9 {
 
         RawModuleDefV9 {
             tables: to_raw(tables, |table: &RawTableDefV9| &table.name),
-            reducers: to_raw(reducers, |reducer: &RawReducerDefV9| &reducer.name),
+            reducers: reducers.into_iter().map(|(_, def)| def.into()).collect(),
             types: to_raw(types, |type_: &RawTypeDefV9| &type_.name),
             misc_exports: vec![],
             typespace,

crates/schema/src/def/validate/v9.rs

@@ -729,7 +729,7 @@ fn identifier(name: Box<str>) -> Result<Identifier> {
 
 fn check_scheduled_reducers_exist(
     tables: &IdentifierMap<TableDef>,
-    reducers: &IdentifierMap<ReducerDef>,
+    reducers: &IndexMap<Identifier, ReducerDef>,
 ) -> Result<()> {
     tables
         .values()