[App] Stop App when it has succeeded (#15801)

(cherry picked from commit 3a99a25)

Author: tchaton

src/lightning_app/CHANGELOG.md

@@ -49,6 +49,9 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Fixed the PyTorch Inference locally on GPU ([#15813](https://github.com/Lightning-AI/lightning/pull/15813))
 
 
+- Fixed the work not stopped when successful when passed directly to the LightningApp ([#15801](https://github.com/Lightning-AI/lightning/pull/15801))
+
+
 ## [1.8.2] - 2022-11-17
 
 ### Added

src/lightning_app/core/flow.py

@@ -758,6 +758,9 @@ def __init__(self, work):
         self.work = work
 
     def run(self):
+        if self.work.has_succeeded:
+            self.work.stop()
+            self._exit()
         self.work.run()
 
     def configure_layout(self):

tests/tests_app/core/test_lightning_app.py

@@ -1134,3 +1134,14 @@ def test_lightning_flow_properties():
     assert flow._value is None
     flow.run()
     assert flow._value is True
+
+
+class SimpleWork2(LightningWork):
+    def run(self):
+        pass
+
+
+def test_lightning_work_stopped():
+
+    app = LightningApp(SimpleWork2())
+    MultiProcessRuntime(app, start_server=False).dispatch()