Map image layer within a web map item does not return 'layers'

[PRichardson-CORE]

Describe the bug
Map image layer within a web map does not return sub layers if the layer has not been configured with anything in the web map. The web map specification does not hydrate the web map item for these map image layers if there is no configuration, and requires an extra call to the map image layer item to get the sub layers.

To Reproduce
Steps to reproduce the behavior:

Add a map image layer with multiple layers within it to a new web map and save (do nothing else). Then run the below snippet.

from arcgis.gis import GIS
gis = GIS()
wm_item = gis.content.get('<itemid>')
lyrs = wm_item.get_data()['operationalLayers']
for operational_lyr in lyrs:
	if 'layers' in operational_lyr:
		# this should be unreachable
		print(operational_lyr['layers'])

Then, to compare behavior, go back to that web map in map viewer and enable popups on one of the sublayers. Re-run the snippet above and it will have the 'layers' key returned.

error:
N/A

Expected behavior
The map image layer in the web map item should have the 'layers' returned without having to manually configure anything on the sublayer first in Map Viewer.

Platform (please complete the following information):

• OS: Windows
• Browser: Edge
• Python API Version [e.g. 1.6.2]: 2.4.1.1

Additional context
If you cannot get the sublayers from the map image layer via the web map item, you cannot update that sublayer in that specific web map without manually configuring one of the sublayers in Map Viewer first.

[nanaeaubry]

@PRichardson-CORE
Hi we have taken a look at this issue and we do see that the get_data call does not always populate the 'layers' key under the 'operationalLayers' unless popup information or other properties have been defined on the layers.

What we see is that if our layers are populated from vector data then popup information is defined by default when saved in a map, thus showing them in the get_data call.

How are you publishing the Map Image Layer? Are the underlying layers vector or raster data or both?

cc @jyaistMap

[PRichardson-CORE]

@nanaeaubry the underlying data being published is vector data.