From 4eb973e5888e0362d4554dccfffea5b6941ae41d Mon Sep 17 00:00:00 2001
From: Philipp Rudiger <prudiger@anaconda.com>
Date: Sun, 13 Sep 2020 10:45:33 -0400
Subject: [PATCH] Wait until JS dependency is loaded before rendering (#1577)

---
 panel/_templates/doc_nb_js.js |  4 ++--
 panel/config.py               | 11 +++++++++++
 panel/io/notebook.py          |  4 ++++
 3 files changed, 17 insertions(+), 2 deletions(-)

diff --git a/panel/_templates/doc_nb_js.js b/panel/_templates/doc_nb_js.js
index d49d112876..da31b421e8 100644
--- a/panel/_templates/doc_nb_js.js
+++ b/panel/_templates/doc_nb_js.js
@@ -4,12 +4,12 @@
     var render_items = {{ render_items }};
     root.Bokeh.embed.embed_items_notebook(docs_json, render_items);
   }
-  if (root.Bokeh !== undefined && root.Bokeh.Panel !== undefined) {
+  if (root.Bokeh !== undefined && root.Bokeh.Panel !== undefined{% for req in requirements %} && root['{{ req }}'] !== undefined {% endfor %}) {
     embed_document(root);
   } else {
     var attempts = 0;
     var timer = setInterval(function(root) {
-      if (root.Bokeh !== undefined && root.Bokeh.Panel !== undefined) {
+      if (root.Bokeh !== undefined && root.Bokeh.Panel !== undefined{% for req in requirements %} && root['{{ req }}'] !== undefined{% endfor %}) {
         clearInterval(timer);
         embed_document(root);
       } else if (document.readyState == "complete") {
diff --git a/panel/config.py b/panel/config.py
index fb878a6ddc..43474b1f1d 100644
--- a/panel/config.py
+++ b/panel/config.py
@@ -412,6 +412,17 @@ class panel_extension(_pyviz_extension):
                 'echarts': 'panel.models.echarts',
                 'ipywidgets': 'ipywidgets_bokeh.widget'}
 
+    # Check whether these are loaded before rendering
+    _globals = {
+        'deckgl': 'deck',
+        'echarts': 'echarts',
+        'katex': 'katex',
+        'mathjax': 'MathJax',
+        'plotly': 'Plotly',
+        'vega': 'vega',
+        'vtk': 'vtk'
+    }
+
     _loaded_extensions = []
 
     def __call__(self, *args, **params):
diff --git a/panel/io/notebook.py b/panel/io/notebook.py
index 835351841c..cee33606f3 100644
--- a/panel/io/notebook.py
+++ b/panel/io/notebook.py
@@ -129,15 +129,19 @@ def render_template(document, comm=None, manager=None):
 def render_model(model, comm=None):
     if not isinstance(model, Model):
         raise ValueError("notebook_content expects a single Model instance")
+    from ..config import panel_extension as pnext
 
     target = model.ref['id']
 
     (docs_json, [render_item]) = standalone_docs_json_and_render_items([model], True)
     div = div_for_render_item(render_item)
     render_item = render_item.to_json()
+    requirements = [pnext._globals[ext] for ext in pnext._loaded_extensions
+                    if ext in pnext._globals]
     script = DOC_NB_JS.render(
         docs_json=serialize_json(docs_json),
         render_items=serialize_json([render_item]),
+        requirements=requirements
     )
     bokeh_script, bokeh_div = script, div
     html = "<div id='{id}'>{html}</div>".format(id=target, html=bokeh_div)