getETag

Returns the bare ETag value from the ETag response header, with surrounding quotes stripped, suitable for use as an If-Match validator.

Returns null if the header is absent or carries a weak validator (W/"..."). The only consumers of this value in the codebase feed it to If-Match, which requires the strong comparison function (RFC 7232 §3.1): a weak validator can never match, so sending it guarantees a 412 Precondition Failed. Some servers (e.g. Node Solid Server / solidcommunity.net) emit only weak ETags for RDF resources; reporting null here makes those writes fall back to unconditional, which is the correct behaviour for a weak validator.