Merging array elements with two different schemas

[mssanjay]

Hi,
I have two YAML files with different schemas and I like to merge a specific array elements from second file into the first file.

file1.yaml

mgwaskong:
  kong:
    dblessConfig:
      config:
        services: []

file2.yaml

services:
 - name: service1
    url: url1
 - name: service2
   url: url2

How can I merge services from file2.yaml into services from file1.yaml?

Thanks
sanjay

[mikefarah]

TLDR:

yq ea '
  (select(fi==0) | .mgwaskong.kong.dblessConfig.config.services) = (select(fi==1) | .services) | 
  select(fi==0)
' examples/data1.yaml examples/data2.yaml

Explanation:

• use ea (eval-all) to load all file in memory.
• select the first file select(fi==0), pipe into the path you want to update .mgwaskong.kong.dblessConfig.config.services. This is in brackets so it becomes the LHS of the = operator
• on the RHS, we select the second file and path we want to set.
• after the update, we filter context to only include the first file

Note that in place of = you can use += if you want to append to an existing array, * to merge etc.