Template Update: overwrites / removes existing data

[stee-re]

Subject of the issue

Updates to existing Data Type templates can result in data loss. E.g. Adding a DO to a LNodeType can result in some of the structures the LNodeType references, get removed.

Your environment

• Version of CoMPAS: https://demo.compas.energy/
• Which browser and its version: Chrome (latest)

Steps to reproduce
Attached file was used for reproducing this issue:
SclTemplateUpdate-dropped-elements-bug.zip

1. Open the attached SCD file in OpenSCD
2. Verify the SCD file is valid before changing anything
3. If not already present, add the "Template Update" plugin
4. In the Template plugin, select PDIS$oscd$_...
5. Select Mod
6. Add some Enums for the ctlModel

7. Add some Enums for the stVal 8. Click on the "Update Logical Node Type" fab button 9. Re-run the validator

Expected behaviour
The LNodeType is updated correctly, such that the element as exactly the same (unchanged children) + the addition of the Mod DOType.

Actual behaviour
The SCL file is no longer Schema Valid:

Additionally - I believe the existing LNodeType should remain "as-is" in case its already being referenced - as we cannot assume all places where it is currently being referenced, actually want (or can support) and updated version of this LNodeType. But perhaps this should be raised as another bug - unless this is now "by design" how it should be.

<LNodeType lnClass="PDIS" desc="Distance" id="PDIS$oscd$_6d6fe5ccce4bb658">
	<DO name="Beh" type="Beh$oscd$_c6ed035c8137b35a"/>
	<DO name="Op" type="Op$oscd$_8598a343000a4c8c" transient="true"/>
	<DO name="Str" type="Str$oscd$_ba49448ecb46113a"/>
	<DO name="DirMod" type="DirMod$oscd$_586debcdfc6172b8"/><!-- missing -->
	<DO name="GndDlTmms" type="GndDlTmms$oscd$_f1c0d370e7430e0c"/><!-- missing -->
	<DO name="PhDlTmms" type="PhDlTmms$oscd$_f1c0d370e7430e0c"/><!-- missing -->
	<DO name="Mod" type="Mod$oscd$_a9263163d22902bb"/>
</LNodeType>

The following DOTypes were removed:

• DirMod$oscd$_586debcdfc6172b8
• GndDlTmms$oscd$_f1c0d370e7430e0c
• PhDlTmms$oscd$_f1c0d370e7430e0c
  The reset remained.