fix MicrobatchExecutionDebug message (#11071) (#11120)

* fix MicrobatchExecutionDebug message

* Fix typing in `describe_batch` to convince mypy `batch_start` exists when needed

---------

Co-authored-by: Quigley Malcolm <[email protected]>
(cherry picked from commit fc6167a)

Co-authored-by: Michelle Ark <[email protected]>

.changes/unreleased/Fixes-20241209-113806.yaml

@@ -0,0 +1,6 @@
+kind: Fixes
+body: Fix debug log messages for microbatch batch execution information
+time: 2024-12-09T11:38:06.972743-06:00
+custom:
+  Author: MichelleArk QMalcolm
+  Issue: "11111"

core/dbt/task/run.py

@@ -376,10 +376,21 @@ def set_relation_exists(self, relation_exists: bool) -> None:
     def set_batches(self, batches: Dict[int, BatchType]) -> None:
         self.batches = batches
 
+    @property
+    def batch_start(self) -> Optional[datetime]:
+        if self.batch_idx is None:
+            return None
+        else:
+            return self.batches[self.batch_idx][0]
+
     def describe_node(self) -> str:
         return f"{self.node.language} microbatch model {self.get_node_representation()}"
 
-    def describe_batch(self, batch_start: datetime) -> str:
+    def describe_batch(self) -> str:
+        batch_start = self.batch_start
+        if batch_start is None:
+            return ""
+
         # Only visualize date if batch_start year/month/day
         formatted_batch_start = MicrobatchBuilder.format_batch_start(
             batch_start, self.node.config.batch_size
@@ -393,8 +404,7 @@ def print_batch_result_line(
         if self.batch_idx is None:
             return
 
-        batch_start = self.batches[self.batch_idx][0]
-        description = self.describe_batch(batch_start)
+        description = self.describe_batch()
         group = group_lookup.get(self.node.unique_id)
         if result.status == NodeStatus.Error:
             status = result.status
@@ -426,7 +436,7 @@ def print_batch_start_line(self) -> None:
         if batch_start is None:
             return
 
-        batch_description = self.describe_batch(batch_start)
+        batch_description = self.describe_batch()
         fire_event(
             LogStartBatch(
                 description=batch_description,
@@ -828,14 +838,14 @@ def _submit_batch(
         if not force_sequential_run and batch_runner.should_run_in_parallel():
             fire_event(
                 MicrobatchExecutionDebug(
-                    msg=f"{batch_runner.describe_batch} is being run concurrently"
+                    msg=f"{batch_runner.describe_batch()} is being run concurrently"
                 )
             )
             self._submit(pool, [batch_runner], batch_results.append)
         else:
             fire_event(
                 MicrobatchExecutionDebug(
-                    msg=f"{batch_runner.describe_batch} is being run sequentially"
+                    msg=f"{batch_runner.describe_batch()} is being run sequentially"
                 )
             )
             batch_results.append(self.call_runner(batch_runner))