Review comments

Author: Sushisource

core-api/src/worker.rs

@@ -225,6 +225,19 @@ impl WorkerConfigBuilder {
             }
         }
 
+        if matches!(self.max_outstanding_workflow_tasks.as_ref(), Some(Some(v)) if *v == 0) {
+            return Err("`max_outstanding_workflow_tasks` must be > 0".to_owned());
+        }
+        if matches!(self.max_outstanding_activities.as_ref(), Some(Some(v)) if *v == 0) {
+            return Err("`max_outstanding_activities` must be > 0".to_owned());
+        }
+        if matches!(self.max_outstanding_local_activities.as_ref(), Some(Some(v)) if *v == 0) {
+            return Err("`max_outstanding_local_activities` must be > 0".to_owned());
+        }
+        if matches!(self.max_outstanding_nexus_tasks.as_ref(), Some(Some(v)) if *v == 0) {
+            return Err("`max_outstanding_nexus_tasks` must be > 0".to_owned());
+        }
+
         if let Some(cache) = self.max_cached_workflows.as_ref() {
             if *cache > 0 {
                 if let Some(Some(max_wft)) = self.max_outstanding_workflow_tasks.as_ref() {
@@ -288,8 +301,8 @@ impl WorkerConfigBuilder {
 /// For more, see the docstrings of the traits in the return types of its functions.
 pub trait WorkerTuner {
     /// Return a [SlotSupplier] for workflow tasks. Note that workflow task slot suppliers must be
-    /// willing to hand out a minimum of two slots if workflow caching is enabled, otherwise the
-    /// worker may fail to process new tasks.
+    /// willing to hand out a minimum of one non-sticky slot and one sticky slot if workflow caching
+    /// is enabled, otherwise the worker may fail to process new tasks.
     fn workflow_task_slot_supplier(
         &self,
     ) -> Arc<dyn SlotSupplier<SlotKind = WorkflowSlotKind> + Send + Sync>;
@@ -414,11 +427,6 @@ impl SlotSupplierPermit {
     pub fn user_data_mut<T: Any + Send + Sync>(&mut self) -> Option<&mut T> {
         self.user_data.as_mut().and_then(|b| b.downcast_mut())
     }
-
-    /// Deconstruct this permit and return the inner data
-    pub fn into_user_data(self) -> Option<Box<dyn Any + Send + Sync>> {
-        self.user_data
-    }
 }
 
 #[derive(Debug, Copy, Clone, derive_more::Display, Eq, PartialEq)]