2

This question is about YTT. Is it possible to modify YAML list of items using the data from that items via overlays?

For example we have a template:

---
vlans:
- vlan-id: 10
- vlan-id: 20
- vlan-id: 30
some_other_configuration: #! some other config here

And using overlays we need to transform the template above into this:

---
vlans:
- vlan-id: 10
  vlan-name: vlan10
- vlan-id: 20
  vlan-name: vlan20
- vlan-id: 30
  vlan-name: vlan30
some_other_configuration: #! some other config here
Anton M.
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1 Answers1

0

Yes. One can use an overlay within an overlay. 

#@ load("@ytt:overlay", "overlay")

#@ def with_name(vlan):
#@overlay/match missing_ok=True
vlan-name: #@ "vlan{}".format(vlan["vlan-id"])
#@ end

#@overlay/match by=overlay.all
---
vlans:
#@overlay/match by=lambda idx, left, right: "vlan-id" in left, expects="1+"
#@overlay/replace via=lambda left, right: overlay.apply(left, with_name(left))
-

which can be read:

  • for all documents,
  • in the vlans: map item...
    • for every array item it contains that has a map that includes the key "vland-id"...
      • replace the map with one that's been overlay'ed with the vlan name

https://carvel.dev/ytt/#gist:https://gist.github.com/pivotaljohn/33cbc52e808422e68c5ec1dc2ca38354

See also:

JTigger
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