jq denormalize a nested field - json

Question

disclaimer: indeed, there are already different answers (like JQ Join JSON files by key or denormalizing JSON with jq) for but none of them helped me yet or did have different circumstances I was unable to derive a solution from ;/
I have 2 files, both are lists of objects where one of them ha field references to object ids of the other one
given
[
{
"id": "5b9f50ccdcdf200283f29052",
"reference": {
"id": "5de82d5072f4a72ad5d5dcc1"
}
}
]
and
[
{
"id": "5de82d5072f4a72ad5d5dcc1",
"name": "FooBar"
}
]
my goal would be to get a denormalized object list:
expected
[
{
"id": "5b9f50ccdcdf200283f29052",
"reference": {
"id": "5de82d5072f4a72ad5d5dcc1",
"name": "FooBar"
}
}
]
while I'm able to do the main parts, I didn't challenged to bring both together yet:
with
example 1
jq -s '(.[1][] | select(.id == "5de82d5072f4a72ad5d5dcc1"))' objects.json referredObjects.json
I get
{
"id": "5de82d5072f4a72ad5d5dcc1",
"name": "FooBar"
}
and with
example 2
jq -s '.[0][] | .reference = {}' objects.json referredObjects.json
I can manipulate any .reference getting
{
"id": "5b9f50ccdcdf200283f29052",
"reference": {}
}
(even I loose the list structure)
But: I can't do s.th. like
execpted "join"
jq -s '.[0][] as $obj | $obj.reference = (.[1][] | select(.id == $obj.reference.id))' objects.json referredObjects.json
even approaches with foreach or reduce looks promising
jq -s '[foreach .[0][] as $obj ({}; .reference.id = ""; . + $obj )]' objects.json referredObjects.json
=>
[
{
"reference": {
"id": "5de82d5072f4a72ad5d5dcc1"
},
"id": "5b9f50ccdcdf200283f29052"
}
]
where I expected to get the same as in second example
I end up in headaches and looking forward to write a ineffective while routine in any language ... hopefully I would appreciate any help on this
~Marcel

Answer 1

Transform the second file into an object where ids and names are paired and use it as a reference while updating the first file.
$ jq '(map({(.id): .}) | add) as $idx
| input
| map_values(.reference = $idx[.reference.id])' file2 file1
[
{
"id": "5b9f50ccdcdf200283f29052",
"reference": {
"id": "5de82d5072f4a72ad5d5dcc1",
"name": "FooBar"
}
}
]

Answer 2

The following solution uses the same strategy as used in the solution by #OguzIsmail but uses the built-in function INDEX/2 to construct the dictionary from the second file.
The important point is that this strategy allows the arrays in both files to be of arbitrary size.
Invocation
jq --argfile file2 file2.json -f program.jq file1.json
program.jq
INDEX($file2[]; .id) as $dict
| map(.reference.id as $id | .reference = $dict[$id])