Merge two Apache Avro schemas containing a common array using jq - shell

Question

I've got two Apache Avro schemas (essentially JSON) - one being a "common" part across many schemas and another one as an . Looking for a way to merge them in a shell script.
base.avsc
{
"type": "record",
"fields": [
{
"name": "id",
"type": "string"
}
]
}
schema1.avsc
{
"name": "schema1",
"namespace": "test",
"doc": "Test schema",
"fields": [
{
"name": "property1",
"type": [
"null",
"string"
],
"default": null,
"doc": "Schema 1 specific field"
}
]
}
jq -s '.[0] * .[1]' base.avsc schema1.avsc doesn't merge the array for me:
{
"type": "record",
"fields": [
{
"name": "property1",
"type": [
"null",
"string"
],
"default": null,
"doc": "Schema 1 specific field"
}
],
"name": "schema1",
"namespace": "test",
"doc": "Test schema"
}
I don't expect to have same keys in the "fields" array. And "type": "record", could be moved into schema1.avsc if that makes it easier.
An expected result should be something like this (the order of the keys doesn't make a difference)
{
"name": "schema1",
"namespace": "test",
"doc": "Test schema",
"type": "record",
"fields": [
{
"name": "property1",
"type": [
"null",
"string"
],
"default": null,
"doc": "Schema 1 specific field"
},
{
"name": "id",
"type": "string"
}
]
}
Can't figure out how to write an expression in jq for what I want.

Answer 1

You need an addition (+) operator to perform a union of records from both the files and combine the common record fields from both the files as
jq -s '.[0] as $o1 | .[1] as $o2 | ($o1 + $o2) |.fields = ($o2.fields + $o1.fields) ' base.avsc schema1.avsc
Answer adopted from pkoppstein's comment on this GitHub post Merge arrays in two json files.
The jq manual says this under the addition operator +
Objects are added by merging, that is, inserting all the key-value pairs from both objects into a single combined object. If both objects contain a value for the same key, the object on the right of the + wins. (For recursive merge use the * operator.)

Answer 2

Here's a concise solution that avoids "slurping":
jq --argfile base base.avsc '
$base + .
| .fields += ($base|.fields)
' schema1.avsc
Or you could go with brevity:
jq -s '
.[0].fields as $f | add | .fields += $f
' base.avsc schema1.avsc

Answer 3

as an alternative solution, you may consider handling hierarchical json using a walk-path based unix utility jtc.
the ask here is mere a recursive merge, which with jtc looks like this:
bash $ <schema1.avsc jtc -mi base.avsc
{
"doc": "Test schema",
"fields": [
{
"default": null,
"doc": "Schema 1 specific field",
"name": "property1",
"type": [
"null",
"string"
]
},
{
"name": "id",
"type": "string"
}
],
"name": "schema1",
"namespace": "test",
"type": "record"
}
bash $
PS> Disclosure: I'm the creator of the jtc - shell cli tool for JSON operations