Replace multi-line plain text

Question

Assuming you have plenty of yaml files (or anything similar) and you want to add a description to all objects with a given name, e.g.

- name: alan
  age: 8

- name: britney # some comment about britney
  hobbies: ["painting", "CS"]
  age: 21

- name: charles # some comment about charles
                # that spans over multiple lines
  age: 42

And I have a list of objects with names that require a description, e.g.

britney: teamblue
charles: foobar

How can I add a line with a description to reach the following:

- name: alan
  age: 8

- name: britney # some comment about britney
  hobbies: ["painting", "CS"]
  age: 21
  description: teamblue

- name: charles # some comment about charles
                # that spans over multiple lines
  age: 42
  description: foobar

So far I go pretty close but I keep failing at replacing a multiline plain text with another:

s=$(awk "/${name}/" RS= ./*.yml)
r=$(awk "/${name}/" RS= ./*.yml && echo "  description: ${desc}")

I need to somehow look for $s and replace it with $r and I cannot make it work. I tried multiple variations of the following two:

sed "s/$s/$r/" ./*.yml
perl -i -0pe "s/$s/$r/" ./*.yml

But somehow the special characters (newlines, double quotes, ...) in the yaml break them and I either get an error message like unterminated substitute pattern or the output is the same and nothing was matched.

Also maybe relevant for sed, I'm using macOS.

Answer 1

$ cat tst.awk
NR==FNR {
    sub(/:/,"",$1)
    map[$1] = $2
    next
}
$3 in map {
    $0 = $0 "\n  description: " map[$3]
}
{ print }

.

$ awk -f tst.awk list RS= ORS='\n\n' foo.yaml
- name: alan
  age: 8

- name: britney # some comment about britney
  hobbies: ["painting", "CS"]
  age: 21
  description: teamblue

- name: charles # some comment about charles
                # that spans over multiple lines
  age: 42
  description: foobar

The above used these input files:

$ cat list
britney: teamblue
charles: foobar

.

$ cat foo.yaml
- name: alan
  age: 8

- name: britney # some comment about britney
  hobbies: ["painting", "CS"]
  age: 21

- name: charles # some comment about charles
                # that spans over multiple lines
  age: 42