Calling setStyle doesn't clear previously set root properties.

[tristen]

In this example, I have two stylesheets with terrain properties that look like this:

// Version A
{
  source: 'mapbox://mapbox.mapbox-terrain-dem-v1',
  exaggeration: 500
}

// Version B
{
  source: 'mapbox://mapbox.mapbox-terrain-dem-v1'
}

Calling setStyle to replace version A with version B results in a situation where exaggeration is still set to 500 and not the default value of 1

Demo to reproduce: https://jsfiddle.net/tristen/ucpynakb/
Version: Latest stable v2.8.2

[avpeery]

Likely related to #11916

[avpeery]

In addition, when setting "exaggeration" in style b, it overwrites the "exaggeration" value in style a. See codepen (click map to toggle styles): https://codepen.io/avpeery/pen/OJQzmrG

[tristen]

@avpeery yeah, I think this is the case for all root properties. If the next style doesn't contain a previously set property, it's not discarded. My expectation is that the default value would be used if the property is no longer present.

If exaggeration is set in both styles the behavior seems right? That properties value overwrites the other.

[avpeery]

@tristen The codepen example has exaggeration set in both style a and style b. If you click the map in the code pen example from style a to style b to style a again, style a’s exaggeration is overwritten to be style b’s exaggeration. I feel like this should not be expected behavior?

I opened a PR that prevents overwriting stylesheet properties (and includes setting the default value for the style terrain exaggeration if not present).

[tristen]

If you click the map in the code pen example from style a to style b to style a again, style a’s exaggeration is overwritten to be style b’s exaggeration

Ah! I missed that in the example you shared. Not expected no 😛

[tristen]

@avpeery can we mark this as a release blocker to v2.9.0?

[avpeery]

@tristen Discussed this with @karimnaaji and since this has been in a couple of the past releases we were planning on not releasing it with 2.9.0 and waiting for the next beta. Is this very high priority for you?

cc: @karimnaaji

[tristen]

I would consider this a high priority. With globe support in Studio adding broader editing capabilities to root properties than before (like authoring expressions and clearing values) it amplifies this older issue.

[karimnaaji]

Thanks for the feedback @tristen , we'll wrap this one up and include it! The fix is almost ready, we just need to make sure to carefully profile it as it can have a performance impact.