yq add property to object somewhere in the tree - yaml

Question

I'm trying to add a response to all objects with the key responses in an open api yaml file. I tried a lot and failed hard because I think I miss some basic understanding but I don't know what exactly.
File
openapi: 3.0.1
info:
title: my service
description: API for my service
version: 1.0.0
security:
- jwt:
- read
paths:
'/foo/{fooId}/firmware/update-request':
post:
parameters:
- name: fooId
in: path
description: Foo Id
required: true
schema:
type: string
requestBody:
content:
application/json:
schema:
$ref: '#/components/schemas/FooRequest'
example:
firmwareVersion: "0.1"
responses:
'202':
description: Foo has been done
'400':
$ref: '#/components/responses/BadRequest'
'409':
$ref: '#/components/responses/Conflict'
'401':
$ref: '#/components/responses/Unauthorized'
'403':
$ref: '#/components/responses/Forbidden'
'404':
$ref: '#/components/responses/NotFound'
'500':
$ref: '#/components/responses/ServerError'
'502':
$ref: '#/components/responses/BadGateway'
'/foo/{fooId}/firmware/auto-update':
put:
parameters:
- name: fooId
in: path
description: Foo Id
required: true
schema:
type: string
requestBody:
content:
application/json:
schema:
$ref: '#/components/schemas/FooUpdate'
example:
enabled: true
responses:
'204':
description: Foo update
'400':
$ref: '#/components/responses/BadRequest'
'401':
$ref: '#/components/responses/Unauthorized'
'403':
$ref: '#/components/responses/Forbidden'
'404':
$ref: '#/components/responses/NotFound'
'500':
$ref: '#/components/responses/ServerError'
'502':
$ref: '#/components/responses/BadGateway'
# goes on forever
Goal is that every response looks like
responses:
'204':
description: Foo update
# ...
'xxx':
description: yyy
while keeping the file structure intact.
What I tried:
yq -i '.. | select(has("responses")).responses | . += {"xxx": {"description": yyy}}' my.yaml
This was the idea, that came the closet my my expected result. But now every node from root to responses are missing.
What is the correct syntax to tell yq "Do this transformation in place on every node with this name without knowing it's level and without affecting every other node"?

Answer 1

You were almost there. Just wrap the whole search on the LHS into parentheses to eventually retain the outer context:
(.. | select(has("responses")).responses) += {"xxx": {"description": "yyy"}}
Note: I have also wrapped yyy in quotes and simplified | . += to just +=.
You could also just set the xxx field directly:
(.. | select(has("responses")).responses).xxx = {"description": "yyy"}
Both of these assume to be executed with mikefarah/yq. For a kislyuk/yq solution, add a ? to get has("responses")? as .. will also capture non-objects.
This was tested on mikefarah/yq version 4.20.2, and on kislyuk/yq version 3.0.2.