Fix has_served_traffic safety check so it doesn't break notebook deve…

…lopment (#694)

mesop/colab/colab_run.py

@@ -2,12 +2,12 @@
 
 from absl import flags
 
-from mesop.colab import colab_utils
 from mesop.runtime import enable_debug_mode
 from mesop.server.constants import EDITOR_PACKAGE_PATH, PROD_PACKAGE_PATH
 from mesop.server.logging import log_startup
 from mesop.server.server import configure_flask_app
 from mesop.server.static_file_serving import configure_static_file_serving
+from mesop.utils import colab_utils
 from mesop.utils.host_util import get_default_host
 
 

mesop/colab/colab_run_test.py

@@ -3,9 +3,9 @@
 
 import pytest
 
-from mesop.colab import colab_utils
 from mesop.colab.colab_run import colab_run
 from mesop.runtime import runtime
+from mesop.utils import colab_utils
 
 
 class FakeThread:

mesop/colab/colab_show.py

@@ -1,4 +1,4 @@
-from mesop.colab import colab_utils
+from mesop.utils import colab_utils
 
 
 def colab_show(

mesop/runtime/BUILD

@@ -12,5 +12,6 @@ py_library(
         "//mesop/exceptions",
         "//mesop/protos:ui_py_pb2",
         "//mesop/security",
+        "//mesop/utils",
     ] + THIRD_PARTY_PY_FLASK,
 )

mesop/runtime/runtime.py

@@ -8,6 +8,7 @@
 from mesop.exceptions import MesopDeveloperException, MesopUserException
 from mesop.key import Key
 from mesop.security.security_policy import SecurityPolicy
+from mesop.utils import colab_utils
 from mesop.utils.backoff import exponential_backoff
 
 from .context import Context
@@ -61,7 +62,15 @@ def context(self) -> Context:
     return g._mesop_context
 
   def create_context(self) -> Context:
-    self._has_served_traffic = True
+    # If running in prod mode, *always* enable the has served traffic safety check.
+    # If running in debug mode, only enable the has served traffic safety check if
+    # app is not running in IPython / notebook environments.
+    #
+    # We don't want to break iterative development where notebook app developers
+    # will want to register pages after traffic has been served.
+    # Unlike CLI (w/ hot reload), in notebook envs, runtime is *not* reset.
+    if not self.debug_mode or not colab_utils.is_running_ipython():
+      self._has_served_traffic = True
     if len(self._state_classes) == 0:
       states = {EmptyState: EmptyState()}
     else: