From b456cb2b8d7eda95f5870faf3166007c44198828 Mon Sep 17 00:00:00 2001
From: Philipp Rudiger <prudiger@anaconda.com>
Date: Tue, 27 Oct 2020 16:16:51 +0100
Subject: [PATCH] Only run preprocessors once on Templates

---
 panel/pane/base.py     | 7 +++++--
 panel/param.py         | 6 ++++--
 panel/template/base.py | 2 +-
 panel/viewable.py      | 7 +++++--
 4 files changed, 15 insertions(+), 7 deletions(-)

diff --git a/panel/pane/base.py b/panel/pane/base.py
index 8814ab7dcc..846a3c2656 100644
--- a/panel/pane/base.py
+++ b/panel/pane/base.py
@@ -235,7 +235,7 @@ def clone(self, object=None, **params):
             object = old_object
         return type(self)(object, **params)
 
-    def get_root(self, doc=None, comm=None):
+    def get_root(self, doc=None, comm=None, preprocess=True):
         """
         Returns the root model and applies pre-processing hooks
 
@@ -245,6 +245,8 @@ def get_root(self, doc=None, comm=None):
           Bokeh document the bokeh model will be attached to.
         comm: pyviz_comms.Comm
           Optional pyviz_comms when working in notebook
+        preprocess: boolean (default=True)
+          Whether to run preprocessing hooks
 
         Returns
         -------
@@ -255,7 +257,8 @@ def get_root(self, doc=None, comm=None):
             root = self._get_model(doc, comm=comm)
         else:
             root = self.layout._get_model(doc, comm=comm)
-        self._preprocess(root)
+        if preprocess:
+            self._preprocess(root)
         ref = root.ref['id']
         state._views[ref] = (self, root, doc, comm)
         return root
diff --git a/panel/param.py b/panel/param.py
index c059154cef..6f922fbdd3 100644
--- a/panel/param.py
+++ b/panel/param.py
@@ -580,7 +580,7 @@ def select(self, selector=None):
         """
         return super().select(selector) + self.layout.select(selector)
 
-    def get_root(self, doc=None, comm=None):
+    def get_root(self, doc=None, comm=None, preprocess=True):
         """
         Returns the root model and applies pre-processing hooks
 
@@ -590,13 +590,15 @@ def get_root(self, doc=None, comm=None):
           Bokeh document the bokeh model will be attached to.
         comm: pyviz_comms.Comm
           Optional pyviz_comms when working in notebook
+        preprocess: boolean (default=True)
+          Whether to run preprocessing hooks
 
         Returns
         -------
         Returns the bokeh model corresponding to this panel object
         """
         doc = init_doc(doc)
-        root = self.layout.get_root(doc, comm)
+        root = self.layout.get_root(doc, comm, preprocess)
         ref = root.ref['id']
         self._models[ref] = (root, None)
         state._views[ref] = (self, root, doc, comm)
diff --git a/panel/template/base.py b/panel/template/base.py
index bdd25fb3b5..a1dddd988d 100644
--- a/panel/template/base.py
+++ b/panel/template/base.py
@@ -146,7 +146,7 @@ def _init_doc(self, doc=None, comm=None, title=None, notebook=False, location=Tr
         for name, (obj, tags) in self._render_items.items():
             if self._apply_hooks not in obj._hooks:
                 obj._hooks.append(self._apply_hooks)
-            model = obj.get_root(doc, comm)
+            model = obj.get_root(doc, comm, preprocess=False)
             mref = model.ref['id']
             doc.on_session_destroyed(obj._server_destroy)
             for sub in obj.select(Viewable):
diff --git a/panel/viewable.py b/panel/viewable.py
index 3e0b29ff8e..a3a306eea5 100644
--- a/panel/viewable.py
+++ b/panel/viewable.py
@@ -461,7 +461,7 @@ def _server_destroy(self, session_context):
             loc._cleanup(root)
             del state._locations[doc]
 
-    def get_root(self, doc=None, comm=None):
+    def get_root(self, doc=None, comm=None, preprocess=True):
         """
         Returns the root model and applies pre-processing hooks
 
@@ -471,6 +471,8 @@ def get_root(self, doc=None, comm=None):
           Bokeh document the bokeh model will be attached to.
         comm: pyviz_comms.Comm
           Optional pyviz_comms when working in notebook
+        preprocess: boolean (default=True)
+          Whether to run preprocessing hooks
 
         Returns
         -------
@@ -478,7 +480,8 @@ def get_root(self, doc=None, comm=None):
         """
         doc = init_doc(doc)
         root = self._get_model(doc, comm=comm)
-        self._preprocess(root)
+        if preprocess:
+            self._preprocess(root)
         ref = root.ref['id']
         state._views[ref] = (self, root, doc, comm)
         return root