Since 4.29, prunes header document while merging documents

[antonincms]

Describe the bug

Hello,

I constated that since YQ version v4.29.0 (precisely, it works with v4.28.2, do not work with 4.31.2 or latest, but I have other error when running v4.29.x or v4.30.x versions), it prunes my header comment while trying to merge documents using the command yq ea '. as $item ireduce ({}; . * $item )' .

Version of yq: 4.29.0 and above.
Operating system: mac or linux
Installed via: docker or binary

Input Yaml
Concise yaml document(s) (as simple as possible to show the bug, please keep it to 10 lines or less)
header.yml:

# **
# ** This file was automatically generated ...
# ** 
#

data.yml:

foo: bar

Command

This is working :

> docker run --rm -v "${PWD}":/workdir mikefarah/yq:4.28.2 ea '. as $item ireduce ({}; . * $item )' header.yaml data.yaml
# **
# ** This file was automatically generated ...
# **
foo: bar

Where this is not :

> docker run --rm -v "${PWD}":/workdir mikefarah/yq:4.31.2 ea '. as $item ireduce ({}; . * $item )' header.yaml data.yaml
foo: bar

I'm unsure wether this is a bug or expected behavior since 4.29.0, but as we used this feature to add headers to documents, if it is not a bug what would you suggest to do instead ?

[mikefarah]

That is a bug :/ - I'll need time to fix it up - but till then you could use this workaround - add an empty map to the file with the comment:

# **
# ** This file was automatically generated ...
# ** 
#
{}

[antonincms]

If it is a bug we can wait for the fix, but thanks a lot for the workaround 👍