Asset and sensor pages sometimes showing no data on page load

[nhoening]

I seem to experience a bug with the data being displayed on the asset page. It's not reliably reproducible and seems to be worse on Firefox than on Chrome :/

I load the page, and I refresh (F5). Often, the data is not showing (even though it seems to be fetched, looking at the networking console). Selecting a date in the datepicker then works - most of the time.
I refreshed a few times, and there seemed even to be some randomness in this bug.

Data might sometimes appear shortly and then disappear (maybe a rendering problem with all the layers we're making?)

I noticed this when reviewing #467, but I also see it on main. I tried Firefox and Chrome. The latter seems better for the first few reloads, but then also regresses for me.

I'm attaching two screenshots, they were made on Firefox, and on the main branch, after a hard reset (Ctrl-Shift-F5)

[nhoening]

A screenshot from when it worked (selecting the day with data in the picker)

[Flix6x]

I'm running FlexMeasures locally on commit 7874bd7 and looking at the toy-battery asset in Firefox and Chrome.

I have been able to reproduce this bug for the sensor page (as you mentioned it in the issue title). The chart on the sensor page does not have multiple layers, so I don't think it has to do with the layers. It looks like the vegaView variable isn't defined yet when the data fetching promises are done. I'll need to make sure the variable is set up before any of the promises's then blocks try to load the view with data.

So far I haven't been able to reproduce this bug for the asset page, but I'll make sure to implement the fix for both pages.