fix: keep Clippy green on the Rust 1.99 stable toolchain

apps/chat2db-web/src/legacy.rs

@@ -11186,12 +11186,12 @@ mod tests {
 
         let column = &request.new_table.column_list[0];
         assert_eq!(column.primary_key_order, 0);
-        assert!(column.comment.is_empty());
-        assert!(column.char_set_name.is_empty());
+        assert_eq!(column.comment, "");
+        assert_eq!(column.char_set_name, "");
         let index = &request.new_table.index_list[0];
-        assert!(index.index_type.is_empty());
-        assert!(index.comment.is_empty());
-        assert!(index.column_list[0].index_name.is_empty());
+        assert_eq!(index.index_type, "");
+        assert_eq!(index.comment, "");
+        assert_eq!(index.column_list[0].index_name, "");
     }
 
     #[test]

apps/chat2db-web/tests/native_mysql_editable_ddl_docker.rs

@@ -1597,7 +1597,7 @@ async fn verify_transfer_routes(
         entry
             .read_to_string(&mut contents)
             .expect("generated class entry must be UTF-8");
-        assert!(!contents.is_empty());
+        assert_ne!(contents, "");
     }
 
     let generated = directory.join("generated-classes");

crates/chat2db-agent/src/context.rs

@@ -42,6 +42,9 @@ impl fmt::Debug for SummaryError {
 }
 
 /// Optional summarization boundary used only for complete historical turns.
+// `async_trait` stamps `#[must_use]` on the generated boxed futures, which
+// `clippy::double_must_use` rejects because the type is already `#[must_use]`.
+#[allow(clippy::double_must_use)]
 #[async_trait]
 pub trait ContextCompactor: Send + Sync {
     async fn summarize(
@@ -475,7 +478,7 @@ mod tests {
     #[test]
     fn adjacent_users_are_not_a_complete_compaction_turn() {
         let messages = vec![Message::system("s"), Message::user("a"), Message::user("b")];
-        assert!(compactable_turns(&messages).is_empty());
+        assert_eq!(compactable_turns(&messages).len(), 0);
     }
 
     #[test]
@@ -491,7 +494,7 @@ mod tests {
             ),
             Message::user("latest"),
         ];
-        assert!(compactable_turns(&messages).is_empty());
+        assert_eq!(compactable_turns(&messages).len(), 0);
     }
 
     #[test]
@@ -524,7 +527,7 @@ mod tests {
             Message::text(Role::Assistant, "terminal"),
             Message::user("latest"),
         ];
-        assert!(compactable_turns(&missing).is_empty());
+        assert_eq!(compactable_turns(&missing).len(), 0);
 
         let duplicate_call =
             ToolCall::new("duplicate", "query", serde_json::json!({})).expect("valid call");
@@ -548,7 +551,7 @@ mod tests {
             Message::text(Role::Assistant, "terminal"),
             Message::user("latest"),
         ];
-        assert!(compactable_turns(&duplicate).is_empty());
+        assert_eq!(compactable_turns(&duplicate).len(), 0);
     }
 
     #[test]

crates/chat2db-agent/src/provider.rs

@@ -13,6 +13,9 @@ pub type ProviderEventStream =
     Pin<Box<dyn Stream<Item = Result<ProviderEvent, ProviderError>> + Send + 'static>>;
 
 /// Direct model-provider boundary used by the agent loop.
+// `async_trait` stamps `#[must_use]` on the generated boxed futures, which
+// `clippy::double_must_use` rejects because the type is already `#[must_use]`.
+#[allow(clippy::double_must_use)]
 #[async_trait]
 pub trait Provider: Send + Sync {
     /// Identifies the wire family without exposing its DTOs.

crates/chat2db-agent/src/runner.rs

@@ -107,6 +107,9 @@ impl Default for AgentLimits {
 }
 
 /// Host boundary for executing one already-validated tool call.
+// `async_trait` stamps `#[must_use]` on the generated boxed futures, which
+// `clippy::double_must_use` rejects because the type is already `#[must_use]`.
+#[allow(clippy::double_must_use)]
 #[async_trait]
 pub trait ToolExecutor: Send + Sync {
     /// Implementations receive cancellation and must return one bounded

crates/chat2db-contract/src/community_dashboard.rs

@@ -186,7 +186,7 @@ mod tests {
             "refreshCycle": {"unit": "seconds", "value": 30}
         }))
         .expect("dashboard request decodes");
-        assert!(request.chart_ids.is_empty());
+        assert_eq!(request.chart_ids.len(), 0);
         let encoded = serde_json::to_value(request).expect("dashboard request encodes");
         assert_eq!(encoded["name"], "Sales");
         assert_eq!(encoded["refreshCycle"]["value"], 30);

crates/chat2db-core/src/agent/catalog.rs

@@ -545,7 +545,8 @@ mod tests {
                 .await
                 .expect("sessions list after delete")
                 .items
-                .is_empty()
+                .is_empty(),
+            "a deleted session must not be listed"
         );
         let missing = application
             .list_agent_messages(&updated.id, "0", "10")

crates/chat2db-core/src/agent/hub.rs

@@ -504,6 +504,9 @@ impl AgentRunHub {
 
     async fn mark_terminal(&self, entry: &AgentRunEntry) {
         cancel_current_permission(entry).await;
+        // `AtomicU64::fetch_update` is deprecated in favour of `try_update`,
+        // which is unstable before Rust 1.95 while the workspace MSRV is 1.88.
+        #[allow(deprecated)]
         let order = self
             .inner
             .next_terminal_order

crates/chat2db-core/src/datasource_compatibility.rs

@@ -791,7 +791,7 @@ mod tests {
             .expect("JDBC-only registry is valid");
         let application = Application::with_native_drivers_for_test(registry);
 
-        assert!(application.list_drivers().items.is_empty());
+        assert_eq!(application.list_drivers().items.len(), 0);
         let compatibility = application
             .native_driver_compatibility("JDBC_ONLY", NativeDriverAction::Download)
             .expect("JDBC-only compatibility resolves");

crates/chat2db-core/src/driver_pack.rs

@@ -753,7 +753,7 @@ mod tests {
         let directory = TempDir::new().expect("temporary directory");
         let prepared =
             discover_test(&directory.path().join("missing")).expect("missing root is optional");
-        assert!(prepared.inventory().is_empty());
+        assert_eq!(prepared.inventory().len(), 0);
     }
 
     #[test]

crates/chat2db-core/src/native_dm.rs

@@ -594,7 +594,7 @@ mod tests {
             database_query.sql,
             "SELECT NAME AS DATABASE_NAME FROM V$DATABASE"
         );
-        assert!(database_query.parameters.is_empty());
+        assert_eq!(database_query.parameters.len(), 0);
 
         let table_query = list_tables_query("APP' OR 1=1 --", "Order_%")
             .expect("quoted schema names are valid metadata values");

crates/chat2db-core/src/native_driver.rs

@@ -1,3 +1,7 @@
+// `async_trait` stamps `#[must_use]` on the generated boxed futures, which
+// `clippy::double_must_use` rejects because the type is already `#[must_use]`.
+#![allow(clippy::double_must_use)]
+
 use std::{
     collections::{HashMap, HashSet},
     sync::Arc,

crates/chat2db-core/src/operation.rs

@@ -313,6 +313,9 @@ impl OperationHub {
         state.journal.push_back(envelope.clone());
         let _ = entry.live.send(envelope);
         if state.status != OperationStatus::Running {
+            // `AtomicU64::fetch_update` is deprecated in favour of `try_update`,
+            // which is unstable before Rust 1.95 while the workspace MSRV is 1.88.
+            #[allow(deprecated)]
             let terminal_order = self
                 .inner
                 .next_terminal_order

crates/chat2db-core/src/query.rs

@@ -1034,7 +1034,7 @@ mod tests {
 
         assert!(request.error_continue);
         assert_eq!(request.result_set_id, None);
-        assert!(request.database_name.is_empty());
+        assert_eq!(request.database_name, "");
     }
 
     #[test]

crates/chat2db-core/tests/java_community_mysql_product.rs

@@ -691,7 +691,10 @@ async fn verify_sql_tools(application: &Application, datasource_id: &str, databa
         .await
         .expect("Core must invoke real MySQL SQL validation");
     assert!(!validation.valid);
-    assert!(!validation.diagnostics.is_empty());
+    assert!(
+        !validation.diagnostics.is_empty(),
+        "invalid SQL must report diagnostics"
+    );
 
     let source_sql = "select id,label from items where id=1";
     let formatted = application

crates/chat2db-core/tests/java_community_product.rs

@@ -48,7 +48,10 @@ async fn product_services_invoke_the_fixed_community_h2_compatibility_slice() {
         .await
         .expect("Core SQL validation must not require a datasource or JDBC session");
     assert!(!validation.valid);
-    assert!(!validation.diagnostics.is_empty());
+    assert!(
+        !validation.diagnostics.is_empty(),
+        "invalid SQL must report diagnostics"
+    );
 
     let formatted = application
         .format_community_sql(FormatCommunitySqlRequest {
@@ -1095,7 +1098,7 @@ async fn verify_trigger_metadata(
         })
         .await
         .expect("escaped H2 trigger-list identifiers must remain a safe metadata query");
-    assert!(injected_list.items.is_empty());
+    assert_eq!(injected_list.items.len(), 0);
     for trigger_name in ["MISSING_TRIGGER", "AUDIT_TRIGGER' OR '1'='1"] {
         let error = application
             .get_community_trigger(GetCommunityTriggerRequest {

crates/chat2db-core/tests/large_value.rs

@@ -282,7 +282,7 @@ fn binary_chunks_round_trip_and_range_validation_is_closed() {
         .read_chunk("execution-1", token(&preview), 13, 1)
         .expect("offset at the end should be valid");
     assert!(eof.eof);
-    assert!(eof.value.is_empty());
+    assert_eq!(eof.value.len(), 0);
 }
 
 #[test]

crates/chat2db-core/tests/native_mysql_product.rs

@@ -490,7 +490,8 @@ async fn verify_native_workspace_metadata(
             .await
             .expect("table pins must relist")
             .items
-            .is_empty()
+            .is_empty(),
+        "an unpinned table must disappear from the listing"
     );
     assert_java_dormant(application);
 }
@@ -530,7 +531,7 @@ async fn verify_native_metadata(
         })
         .await
         .expect("MySQL schema route must stay native");
-    assert!(schemas.items.is_empty());
+    assert_eq!(schemas.items.len(), 0);
 
     let tables = application
         .list_community_tables(ListCommunityTablesRequest {

crates/chat2db-core/tests/native_oracle_smoke.rs

@@ -261,8 +261,8 @@ async fn verify_database_and_schema_metadata(
         .items
         .first()
         .expect("Oracle must expose its current database");
-    assert!(!database.name.is_empty());
-    assert!(!database.owner.is_empty());
+    assert_ne!(database.name, "");
+    assert_ne!(database.owner, "");
 
     let schemas = application
         .list_community_schemas(ListCommunitySchemasRequest {

crates/chat2db-core/tests/native_postgres_smoke.rs

@@ -198,7 +198,7 @@ async fn verify_oversized_scalar_cleanup(
     datasource_id: &str,
     data_dir: &Path,
 ) {
-    assert!(retained_result_files(data_dir).is_empty());
+    assert_eq!(retained_result_files(data_dir).len(), 0);
     let scalar_bytes = wire::JdbcProtocolLimit::MaxScalarBytes as usize + 1;
     let query = application
         .start_query(StartQueryRequest {

crates/chat2db-java-bridge/src/supervisor/community.rs

@@ -344,7 +344,10 @@ impl CommunityClasspath {
     }
 
     /// Returns the canonical JARs in deterministic classpath order.
-    #[must_use]
+    // A bare `#[must_use]` satisfies `clippy::must_use_candidate` on Rust 1.88
+    // but fails `clippy::double_must_use` on Rust 1.99; the explicit reason
+    // satisfies both.
+    #[must_use = "the canonical classpath order must be consumed"]
     pub fn artifacts(&self) -> impl ExactSizeIterator<Item = &Path> {
         self.artifacts
             .iter()
@@ -2777,6 +2780,9 @@ fn validate_metadata_session(
     Ok(())
 }
 
+// `AtomicU64::fetch_update` is deprecated in favour of `try_update`, which is
+// unstable before Rust 1.95 while the workspace MSRV is 1.88.
+#[allow(deprecated)]
 fn next_sql_completion_datasource_scope() -> Result<u64, BridgeError> {
     NEXT_SQL_COMPLETION_DATASOURCE_SCOPE
         .fetch_update(Ordering::Relaxed, Ordering::Relaxed, next_java_long_scope)

crates/chat2db-java-bridge/tests/java_community_h2.rs

@@ -780,7 +780,7 @@ async fn verify_programmability_metadata(
         .list_function_parameters(session, "H2", database_name, "APP", "ADD_ONE", None)
         .await
         .expect("H2Meta must list function parameters");
-    assert!(function_parameters.is_empty());
+    assert_eq!(function_parameters.len(), 0);
 
     let procedures = community
         .list_procedures(session, "H2", database_name, "APP", None)
@@ -971,14 +971,17 @@ async fn verify_parser(community: &CommunityClient) {
         .expect("Community parser must validate well-formed SQL");
     assert!(valid.valid);
     assert_eq!(valid.statements.len(), 1);
-    assert!(valid.diagnostics.is_empty());
+    assert_eq!(valid.diagnostics.len(), 0);
 
     let invalid = community
         .validate_sql("H2", "SELECT FROM;")
         .await
         .expect("Community parser must return bounded syntax diagnostics");
     assert!(!invalid.valid);
-    assert!(!invalid.diagnostics.is_empty());
+    assert!(
+        !invalid.diagnostics.is_empty(),
+        "invalid SQL must report diagnostics"
+    );
     assert!(
         invalid
             .diagnostics

crates/chat2db-java-bridge/tests/java_jdbc_h2.rs

@@ -522,7 +522,10 @@ async fn collect_rows(session: &Session, sql: &str) -> Vec<JdbcRow> {
         match next_event(&mut stream).await {
             QueryEvent::Started(metadata) => {
                 assert!(!started, "query metadata must be emitted once");
-                assert!(!metadata.columns.is_empty());
+                assert!(
+                    !metadata.columns.is_empty(),
+                    "query metadata must carry columns"
+                );
                 started = true;
             }
             QueryEvent::Batch(batch) => rows.extend(batch.rows),

crates/chat2db-storage/src/agent.rs

@@ -4377,7 +4377,7 @@ mod tests {
         assert_eq!(messages[0].ordinal, 0);
         assert_eq!(messages[0].role, AgentMessageRole::System);
         assert_eq!(messages[0].content_json, message_json("rules"));
-        assert!(!messages[0].id.is_empty());
+        assert_ne!(messages[0].id, "");
         assert!(messages[0].run_id.is_none());
 
         let appended = storage
@@ -4870,7 +4870,8 @@ mod tests {
             storage
                 .list_agent_messages(&session.id, 0, 10)
                 .expect("messages list")
-                .is_empty()
+                .is_empty(),
+            "rejected messages must not be persisted"
         );
     }
 
@@ -6175,7 +6176,8 @@ mod tests {
             storage
                 .list_agent_messages(&session.id, 0, 10)
                 .expect("messages list")
-                .is_empty()
+                .is_empty(),
+            "rejected messages must not be persisted"
         );
 
         storage

crates/chat2db-storage/src/community_dashboard.rs

@@ -1193,7 +1193,8 @@ mod tests {
                 .expect("dashboard reads")
                 .expect("dashboard exists")
                 .chart_ids
-                .is_empty()
+                .is_empty(),
+            "a default dashboard must not define charts"
         );
         assert!(
             storage

crates/chat2db-storage/src/datasource.rs

@@ -1130,7 +1130,8 @@ mod tests {
             storage
                 .list_datasources()
                 .expect("datasources list")
-                .is_empty()
+                .is_empty(),
+            "a rolled back create must not leave datasources behind"
         );
         assert!(vault.values.lock().expect("vault lock").is_empty());
         assert_eq!(storage.reconcile_secrets().expect("queue reads").pending, 0);

crates/chat2db-storage/src/result_store.rs

@@ -1827,7 +1827,7 @@ mod tests {
             .read_result_page(&metadata.id, PageRequest::default())
             .expect("empty page reads");
         assert_eq!(page.schema, schema());
-        assert!(page.rows.is_empty());
+        assert_eq!(page.rows.len(), 0);
         assert!(!page.has_more);
     }