fix(connections): preserve filename and content type in multipart file uploads

[Dennis-UiPath]

Summary

ConnectionsService._build_activity_request_spec currently constructs
files[key] = (key, val, None) for every multipart parameter,
regardless of value type. Two consequences for any connector activity
that uploads a file:

1. Filename is wrong. httpx interprets the first element of a
   3-tuple as the filename for Content-Disposition: form-data; name="…"; filename="…".
   Today every file is uploaded with the form-field name as its
   filename, e.g. attachment[file]. Downstream services that store
   attachments by name end up with literal attachment_file_. (Coupa
   sanitises [/], then appends . because there's no extension).
2. Content-Type is None. httpx then defaults to application/octet-stream,
   so previewers / browsers cannot pick a sensible viewer.

The current source even flags the gap explicitly:

# files not supported yet supported so this will likely not work
files[key] = (
    key,
    val,
    None,
)  # probably needs to extract content type from val since IS metadata doesn't provide it

packages/uipath-platform/src/uipath/platform/connections/_connections_service.py#L791-L796

A real-world manifestation: every Coupa attachment uploaded by an agent using coupa.add_attachment lands as attachment_file_. instead of the document's real filename.

Fix

Branch on the value type to accept httpx's standard tuple shape, while keeping the existing bytes-only path working:

if isinstance(val, tuple):
    # Caller supplied httpx's (filename, content[, content_type])
    # shape — pass through verbatim. This is the recommended path
    # for file uploads.
    files[key] = val
elif isinstance(val, (bytes, bytearray)) or hasattr(val, "read"):
    # Raw file content with no filename — fall back to the form-field
    # name (legacy behaviour). Backwards compatible with callers that
    # still pass bytes directly.
    files[key] = (key, val, "application/octet-stream")
else:
    # Scalar — send as a plain multipart form field, not a file part.
    # The (None, value) shape tells httpx to omit `filename=...` from
    # the Content-Disposition.
    files[key] = (None, str(val))

Caller passes	Wire-level result
("invoice.pdf", b"…", "application/pdf") (recommended)	Content-Disposition: form-data; name="attachment[file]"; filename="invoice.pdf" + Content-Type: application/pdf
("invoice.pdf", b"…") (2-tuple shorthand)	filename preserved, httpx infers content type
b"…" (legacy)	unchanged behaviour: filename = form-field name
"some string" (scalar)	sent as plain form field — filename=… is omitted

Backwards compatible: existing callers passing raw bytes keep working with no observable change on the wire.

Tests

Added TestMultipartFileUpload in packages/uipath-platform/tests/services/test_connections_service.py with four cases that inspect the serialized multipart body:

• test_invoke_activity_multipart_tuple_3_preserves_filename — asserts filename="invoice.pdf" and Content-Type: application/pdf land in the wire body.
• test_invoke_activity_multipart_tuple_2_preserves_filename — 2-tuple shorthand preserves filename.
• test_invoke_activity_multipart_bytes_backwards_compatible — legacy raw-bytes callers keep behaviour: filename = form-field name, application/octet-stream content type.
• test_invoke_activity_multipart_scalar_is_plain_form_field — non-file params (e.g. payload="{}") are emitted without a bogus filename= in Content-Disposition.

Test results

Ran from packages/uipath-platform/:

• uv run pytest tests/services/test_connections_service.py → 57 passed (53 pre-existing + 4 new).
• uv run pytest tests/ → 1105 passed, 7 skipped (the skipped ones are pre-existing LLM integration tests gated on real credentials).
• uv run ruff check src/uipath/platform/connections/_connections_service.py → clean.

Verification that the new tests catch the bug

I git stashed the fix and re-ran pytest …::TestMultipartFileUpload — 3 of the 4 new tests fail against the unpatched serializer (tuple_3, tuple_2, scalar). The bytes-backwards-compat test passes either way, because httpx defaults a None content type to application/octet-stream on the wire.

End-to-end validation

The downstream change in our agent that motivated this — using the patched SDK to send the real document filename to Coupa via add_attachment — was verified end-to-end against the staging Coupa instance: same byte payload as before, but the attachment is now stored with the real filename (invoice_<id>.pdf) instead of attachment_file_..