Allow to see the context of a Unsupported query for a subscription (#621)

Author: mamcx

crates/core/src/error.rs

@@ -7,6 +7,7 @@ use hex::FromHexError;
 use thiserror::Error;
 
 use crate::client::ClientActorId;
+use crate::sql::query_debug_info::QueryDebugInfo;
 use spacetimedb_lib::buffer::DecodeError;
 use spacetimedb_lib::{PrimaryKey, ProductValue};
 use spacetimedb_primitives::{ColId, IndexId, TableId};
@@ -92,6 +93,8 @@ pub enum SubscriptionError {
     Empty,
     #[error("Queries with side effects not allowed: {0:?}")]
     SideEffect(Crud),
+    #[error("Unsupported query on subscription: {0:?}")]
+    Unsupported(QueryDebugInfo),
 }
 
 #[derive(Error, Debug)]

crates/core/src/subscription/query.rs

@@ -1094,7 +1094,10 @@ mod tests {
             "SELECT * FROM lhs JOIN rhs ON lhs.id = rhs.id WHERE lhs.x < 10",
         ];
         for join in joins {
-            assert!(compile_read_only_query(&db, &tx, &auth, join).is_err(), "{join}");
+            match compile_read_only_query(&db, &tx, &auth, join) {
+                Err(DBError::Subscription(SubscriptionError::Unsupported(_))) => (),
+                x => panic!("Unexpected: {x:?}"),
+            }
         }
 
         Ok(())

crates/core/src/subscription/subscription.rs

@@ -33,7 +33,7 @@ use std::time::Instant;
 
 use crate::db::datastore::locking_tx_datastore::MutTxId;
 use crate::db::db_metrics::{DB_METRICS, MAX_QUERY_CPU_TIME};
-use crate::error::DBError;
+use crate::error::{DBError, SubscriptionError};
 use crate::execution_context::{ExecutionContext, WorkloadType};
 use crate::sql::query_debug_info::QueryDebugInfo;
 use crate::subscription::query::{run_query, OP_TYPE_FIELD_NAME};
@@ -94,7 +94,7 @@ pub struct SupportedQuery {
 
 impl SupportedQuery {
     pub fn new(expr: QueryExpr, info: QueryDebugInfo) -> Result<Self, DBError> {
-        let kind = query::classify(&expr).context("Unsupported query expression")?;
+        let kind = query::classify(&expr).ok_or_else(|| SubscriptionError::Unsupported(info.clone()))?;
         Ok(Self { kind, expr, info })
     }
 
@@ -128,7 +128,7 @@ impl AsRef<QueryExpr> for SupportedQuery {
 }
 
 /// A set of [supported][`SupportedQuery`] [`QueryExpr`]s.
-#[derive(Deref, DerefMut, PartialEq, From, IntoIterator)]
+#[derive(Debug, Deref, DerefMut, PartialEq, From, IntoIterator)]
 pub struct QuerySet(BTreeSet<SupportedQuery>);
 
 impl From<SupportedQuery> for QuerySet {