Replace subkey without exact path in jq - json

Question

Example JSON file:
{
"u": "stuff",
"x": [1,2,3],
"y": {
"field": "value"
},
"z": {
"zz": {
"name": "change me",
"more": "stuff"
},
"randomKey": {
"name": "change me",
"random": "more stuff"
}
}
}
How can I update all the name fields to "something", maintaining the rest of the JSON file the same?
{
"u": "stuff",
"x": [1,2,3],
"y": {
"field": "value"
},
"z": {
"zz": {
"name": "something",
"more": "stuff"
},
"randomKey": {
"name": "something",
"random": "more stuff"
}
}
}
With a direct path, this would be easy, but the parent keys (z and randomKey in these case) varies.
I tried something like:
jq '.z | .. | .name? |= "something"' file.json
And it's updating the names, but putting also all the recursive stuff..

Answer 1

If it is acceptable to change the "name" field wherever it occurs, you could use walk/1:
walk(if type == "object" and has("name") then .name = "something" else . end)
Please note that walk/1 was only included with jq after jq 1.5 was released. If your jq does not have it, then you can find its definition on the jq FAQ, for example.
If you only want to modify the "name" field in the "z" context, then consider:
.z |= with_entries(if .value.name?
then .value.name = "something"
else . end)

Answer 2

Assuming every value within z has a name property, you could do this:
$ jq --arg newname 'something' '.z[].name = $newname' input.json
Using [] on an object will yield all the values contained in that object. And for each of those values, we were simply setting the name to the new name.
If you needed to be more selective with what gets updated, you'll have to add more conditions to what objects to update. In general, I'd use peak's approach, but here's another way it could be achieved using a structure similar to the first approach, assuming we only want to update objects that already have a name property:
$ jq --arg newname 'something' '(.z[] | select(has("name")).name) = $newname' input.json
It's important to wrap the LHS of the assignment in parentheses, we don't want to change the context prior to the assignment, otherwise we won't see the rest of the results.