yq/pkg/yqlib/doc/usage/formatting-expressions.md

Formatting Expressions

From version v4.41+

You can put expressions into .yq files, use whitespace and comments to break up complex expressions and explain what's going on.

Using expression files and comments

Given a sample.yaml file of:

a:
  b: old

And an 'update.yq' expression file of:

# This is a yq expression that updates the map
# for several great reasons outlined here.

.a.b = "new" # line comment here
| .a.c = "frog"

# Now good things will happen.

then

yq --from-file update.yq sample.yml

will output

a:
  b: new
  c: frog