How to merge and keep original anchors

[rjshrjndrn]

First of all, thank you for this wonderful project. It makes yaml operations humanly :)

Describe the bug
Yaml merge drop anchors

Version of yq: 4.30.4
Operating system: linux
Installed via: binary-release
Input Yaml
Concise yaml document(s) (as simple as possible to show the bug, please keep it to 10 lines or less)

old_vars.yml:

clickhouse:
  enabled: true

global:
  name: app1

new_vars.yml:

clickhouse: &clickhouse
  enabled: false

global:
  name: app1
  clickhouse: *clickhouse

Command
The command you ran:

 yq '. *= load("old_vars.yaml")' new_vars.yaml

Actual behavior

clickhouse:
  enabled: true
global:
  name: app1
  clickhouse: *clickhouse

Expected behavior

clickhouse:  &clickhouse             #Should have anchor here, like &clickhouse
  enabled: true
global:
  name: app1
  clickhouse: *clickhouse     # This is not a valid alias now

Additional context

I've 2 files, one the customized by me, other one the software updates, usually every release will have small changes in this yaml. I'm using yq to merge these 2 files, but this anchor is becoming a problem.

[mikefarah]

This is intentionally how merge operates, it merges all the nodes (including key nodes) - and the overriding key node does not have an anchor set.

What you need to do is merge in the leaf nodes only - I've had a think about this, and you could do it like so:

yq '(load("old_vars.yaml") | .. | select(tag != "!!map" and tag != "!!seq")) as $i ireduce(.; setpath($i | path; $i))' new_vars.yaml

Explanation:

• We need to select all the leaf nodes of 'old_vars' - ones that aren't maps or sequences
• Then we can use the reduce operator over this nodes, and call setpath on each one, setting the old_var value at that path.

[rjshrjndrn]

Thank you very much. You saved me from some sed hacking 😅