Improve hover for geometries - make it less likely to fail

[jsignell]

Closes #842
I am unsure of how much of this PR overlaps with holoviz/holoviews#5325.

MRE from #842 (slightly augmented to include by="reference_time")

import geopandas
import hvplot.pandas

json_str = '{"type": "FeatureCollection", "features": [{"id": "292", "type": "Feature", "properties": {"reference_time": "2021-08-03T06:00:00"}, "geometry": {"type": "Polygon", "coordinates": [[[6.734387964482268, 50.096981436429836], [6.715702760798321, 50.08350087669019], [6.7164606556881665, 50.07500090230046], [6.726932700709735, 50.06899131283367], [6.727498990205583, 50.062616788193964], [6.730988279570088, 50.06061342371476], [6.7311767879985, 50.05848865569604], [6.748616494592647, 50.048470246593965], [6.749553435189103, 50.0378472878539], [6.7565245571179045, 50.033839329129954], [6.822494229902199, 50.036222772078176], [6.829457117826622, 50.03220914103082], [6.832755487784024, 50.032326768682196], [6.836236195568452, 50.03031965546154], [6.839534418239325, 50.03043703037027], [6.843014579155103, 50.02842967525436], [6.846312654459997, 50.02854679744998], [6.849792268503478, 50.026539200507266], [6.853090196362978, 50.026656070019335], [6.856569263530571, 50.024648231318345], [6.882952088134839, 50.02557774446169], [6.889189529279116, 50.03005826409537], [6.888113617274682, 50.04280701271642], [6.884634555008016, 50.04481630967492], [6.8747356652759315, 50.04446880452035], [6.8712557178674984, 50.04647759882098], [6.8646562244125935, 50.04624505628612], [6.861175560726028, 50.048253478263526], [6.854575813313595, 50.04802018550571], [6.847612674584511, 50.05203617315432], [6.847430905745282, 50.05416109906186], [6.843948557379587, 50.056168944871104], [6.843766557088876, 50.05829391731779], [6.833316605440537, 50.06431684307392], [6.83001537252634, 50.06419921302388], [6.826531128284592, 50.066206501150646], [6.806723163146417, 50.065497367264776], [6.799751515201596, 50.069510039897715], [6.799566902060483, 50.07163509569316], [6.789105952186076, 50.077653323156746], [6.788550085538567, 50.0840288255632], [6.785061709927709, 50.086034734508154], [6.784876167120653, 50.088159975675374], [6.781387200638471, 50.09016579161379], [6.781201425169829, 50.092291079083346], [6.777711867667758, 50.094296801962315], [6.777525859439406, 50.09642213571793], [6.77403571076884, 50.098427765484495], [6.734387964482268, 50.096981436429836]]]}}, {"id": "329", "type": "Feature", "properties": {"reference_time": "2021-08-03T06:15:00"}, "geometry": {"type": "Polygon", "coordinates": [[[6.53500332673663, 50.17262838814129], [6.525676395793689, 50.165864441490726], [6.509130066483161, 50.165217619771184], [6.493598140164972, 50.15393999616791], [6.490290012794701, 50.15380969662393], [6.487184983165786, 50.151553827645586], [6.483877092942987, 50.151423292112206], [6.477668602593298, 50.1469110968444], [6.477872177168287, 50.14478575952954], [6.474768669293165, 50.142529583182], [6.474972387017253, 50.140404309639585], [6.468766845311061, 50.135891799690036], [6.452234991265688, 50.135234543767545], [6.449133859035186, 50.1329776075923], [6.449954293080332, 50.12447741050391], [6.443754499017571, 50.119963601072335], [6.440449599993195, 50.119831480170184], [6.437350486271928, 50.117574347547794], [6.434045824577542, 50.11744199108877], [6.430947304193949, 50.115184668906], [6.4276428798783325, 50.115052076929956], [6.424544952781937, 50.11279456525802], [6.421240765893827, 50.11266173780486], [6.421447405298261, 50.11053697719101], [6.415253448962403, 50.10602157197326], [6.415460396331883, 50.10389691192589], [6.412364153209042, 50.101639131494146], [6.409061010457461, 50.101505861479545], [6.405965360262447, 50.099247891817576], [6.406172804999734, 50.09712334179774], [6.403077699809985, 50.09486533258377], [6.406587622735568, 50.092874323519545], [6.406794995742371, 50.0907498552632], [6.41030432603753, 50.088758750082896], [6.413606331103893, 50.08889196357895], [6.417115116616857, 50.08690061275905], [6.433624670504715, 50.08756418677074], [6.452208535577216, 50.101104117299926], [6.458815082702433, 50.10136733427171], [6.461914147828928, 50.10362349560114], [6.465217670042701, 50.10375480739412], [6.4683173279463855, 50.10601077904516], [6.468113416590205, 50.108135588575635], [6.480516509589828, 50.1171588550765], [6.483821311675101, 50.11728948785017], [6.48692324762389, 50.11954499954339], [6.506753830987399, 50.120325544782304], [6.516065757468713, 50.12708957980573], [6.519371575991884, 50.127218901978026], [6.522476524780929, 50.129473313114914], [6.529088657857204, 50.129731363130404], [6.535300548774286, 50.13423950078656], [6.5340989899325645, 50.146991888717444], [6.537206508245576, 50.149246060243634], [6.537006334657516, 50.15137159007232], [6.540114400713651, 50.1536257208377], [6.539714318626019, 50.15787693505321], [6.542823099854781, 50.16013106138122], [6.541823326839114, 50.170759755944204], [6.538313303264706, 50.17275704375211], [6.53500332673663, 50.17262838814129]]]}}]}'
small_dataset = geopandas.read_file(json_str)

small_dataset.hvplot(geo=False, groupby="reference_time") # works but has a weird empty hover
small_dataset.hvplot(geo=True, groupby="reference_time") # does not work
small_dataset.hvplot(geo=False, by="reference_time") # does not work
small_dataset.hvplot(geo=True, by="reference_time") # does not work

With this PR:

[hoxbro]

I just tested your PR and the current main with the latest main on Holoviews and Geoviews:

code	hvplot main	#1055
geo=False + groupby	Works but weird hover	Works no hover
geo=True + groupby	Errors	Works no hover
geo=False + by	Works with hover	Works no hover
geo=True + by	Works with hover	Works no hover

I will cut a dev release for holoviews and geoviews, so you don't have to second-guess your great work.

[jsignell]

Is there anything that I need to change on this one?

[maximlt]

I'm sure the code handling these multiple options (hover + geom + by/groupby ...) has some other weaknesses and could be improved but this requires a deeper dive. Thanks for this PR as it indeed makes things less likely to fail which is a lot better!