Combination of "export_png()" and "show()" causes error

[jnettels]

Hi there!
It pains me to bring up these export_png-related issues... but here I go again. This time it is an error that shows up when using export_png() and show() together:

In 0.13.0, the following works just fine:

from bokeh.models import ColumnDataSource
from bokeh.plotting import figure
from bokeh.layouts import layout
from bokeh.io import export_png, show, output_file

source = ColumnDataSource({'x': [2, 3, 4], 'y': [0.5, 1.5, 2.5]})
fig = figure(plot_width=1000, plot_height=300)
fig.hbar(y='y', right='x', height=0.4, source=source)

export_png(fig, filename="export fig.png")

doc_layout = layout([fig])

output_file('export_test.html', title='export test')
show(doc_layout)

...but in 1.0.0, it throws the following error for the line show(doc_layout):
RuntimeError: Models must be owned by only a single document, HelpTool(id='1026', ...) is already in a doc

Some observations:

• I wonder if it has to do with the changes that allowed to fix export_png not exporting figures correctly #8020.
• Not using either export_png or show works.
• Using show(fig) instead of show(doc_layout) works, as well (but that is not really a workaround).
• Using export_png after show works, too. This could be a workaround in most use cases, but is quite inconvenient in mine.

Many thanks for the 1.0 release, anyway. I read about it in the change log, and it really feels like the export function is now faster for multiple exports!

[bryevdv]

This diff fixes:

diff --git a/bokeh/embed/util.py b/bokeh/embed/util.py
index 36333a39c..e0c610f03 100644
--- a/bokeh/embed/util.py
+++ b/bokeh/embed/util.py
@@ -113,7 +113,7 @@ def OutputDocumentFor(objs, apply_theme=None, always_new=False):

     def finish(): pass

-    docs = set(x.document for x in objs)
+    docs = _compute_current_docs(objs)

     # handle a single shared document, or missing document
     if len(docs) == 1:
@@ -317,6 +317,14 @@ be used. For more information on building and running Bokeh applications, see:
     http://bokeh.pydata.org/en/latest/docs/user_guide/server.html
 """

+def _compute_current_docs(objs):
+    docs = set()
+    for obj in objs:
+        docs.add(obj.document)
+        for ref in obj.references():
+            docs.add(ref.document)
+    return docs
+
 def _create_temp_doc(models):
     doc = Document()
     for m in models:

I will submit a PR once I have time to figure out some tests.

[bryevdv]

closed by #8386