Nouveau: Emitting multiple indexes per field per doc only returns the last indexed value when doing `{"store": true}`

Description

Assume I have many products with an array of colors each. I can index('string', 'color', color[i]) each color from each array individually for a facet search/count, and that works fine, they’re counted correctly. However, if I return the indexed fields with {"store": true}, only the last emitted color per product is returned in the fields section.

Steps to Reproduce

In a CouchDB with activated Nouveau, with a running Nouveau server:

Have some docs with an array of values, eg. "colors": ["mauve", "fuchsia", "ennui"]

Add a Nouveau string index for that key (newlines for readability only):

{
  "_id": "_design/nouveau_example",
  "nouveau": {
    "facets": {
      "index": "function(doc) {
        if (doc.colors) { 
          doc.colors.forEach((color) => 
            index('string', 'color', color, {'store': true})
          )
        }
      }"
    }
  }
}

Send a counts query :

/_design/nouveau_example/_nouveau/facets?q=*:*&counts=["color"]

This returns:

For the doc above:
```
"fields": {
"color": "ennui"
}
```

At the end in the counts:

"counts": {
"color": {
  "mauve": 1,
  "fuchsia": 1,
  "ennui": 1
}
}

Expected Behaviour

Somehow get all colors per doc back in fields.

Your Environment

{
  "couchdb":"Welcome",
  "version":"3.4.1",
  "git_sha":"f504e38a5",
  "uuid":"4e36c505782b7068ead9895902c5f07d",
  "features":[
    "nouveau",
    "access-ready",
    "partitioned",
    "pluggable-storage-engines",
    "reshard",
    "scheduler"
  ],
  "vendor":{"name":"The Apache Software Foundation"}
}

CouchDB version used: 3.4.1 Mac binary
Browser name and version: Requests made using Thunder Client for VS Code
Operating system and version: Mac OS Sonoma 14.6.1

apache / couchdb