[HfApi] Collections in collections

[hanouticelina]

Originally reported by @xeophon in this gist, it wasn't possible to access the collection slug when a collection item was itself a collection, and this was flagged internally by @Vaibhavs10 in this Slack message.

This PR enables proper client-side handling of collections that include collections as items. When the item type is "collection", we now set item_id to the collection’s slug, ensuring consistency with how other item types (model, dataset, space, paper) are handled.

from huggingface_hub import get_collection

# a collection with only collection items
collection_slug = "celinah/inference-providers-function-calling-6826023e8ae9b24b3039ee5f"

print(f"Fetching collection: {collection_slug}")
collection = get_collection(collection_slug)
for i, item in enumerate(collection.items):
    print(f"Item {i + 1}:")
    print(f"  Collection Slug: {item.item_id}")
    print(f"  Object ID: {item.item_object_id}")
    print(f"  Type: {item.item_type}")

for reference, server-side PR here (private link).

[codecov]

Codecov Report

Attention: Patch coverage is 25.00000% with 3 lines in your changes missing coverage. Please review.

Project coverage is 53.80%. Comparing base (1ebdbf9) to head (af1eaa5).
Report is 7 commits behind head on main.

Files with missing lines	Patch %	Lines
src/huggingface_hub/hf_api.py	25.00%	3 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##             main    #3120       +/-   ##
===========================================
- Coverage   76.33%   53.80%   -22.53%     
===========================================
  Files         130      133        +3     
  Lines       12952    13286      +334     
===========================================
- Hits         9887     7149     -2738     
- Misses       3065     6137     +3072     

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[HuggingFaceDocBuilderDev]

The docs for this PR live here. All of your documentation changes will be reflected on that endpoint. The docs are available until 30 days after the last update.

[ghost]

Just ran my scripts, and it does work as expected with this PR. Thank you so, so much!!

[Wauplin]

Thanks!