Per-class table for user classes whose recorded StreamerInfo does not describe the bytes (e.g. KM3NETDAQ::JDAQ* in uproot-issue433-splitlevel*.root) #69

🤖 AI generated content

Follow-on to the element-ordering bug tracked in #67: once JTRIGGER::JPMTSelector reads correctly, uproot-issue433-splitlevel2.root and uproot-issue433-splitlevel4.root are expected to hit a second, separate problem (not yet reproduced here, since the first failure masks it).

Spec: Streamer-driven reading §7 "When the streamer info does not describe the bytes" and gen/foreign/IGNORE.toml: KM3NETDAQ::JDAQPreamble, JDAQSummaryFrame and JDAQSuperFrame are user classes with hand-written Streamers, so the info recorded for them "is fiction". Bootstrap classes §6 makes the general point: the set of classes that need hardcoded handling "cannot be closed", because any user class can have a hand-written streamer.

To do:

• Confirm the failure once Deprecate Python dataclass annotations as the serialization definition for streamer-generated dataclasses #67 lands (which objects, at what nesting level, whether their slots have byte counts).
• Provide one named, documented per-class override table — the same mechanism wanted by RooFit classes with hand-written streamers (RooRealVar, RooLinkedList, ...): implement per root-io-spec RooFit, replacing the framing-layer special cases #71 for the RooFit special cases currently inline in src/rootfilespec/bootstrap/streamedobject.py — whose entries can say "skip as Uninterpreted" (default, see Class missing from StreamerInfo: return Uninterpreted (skip by byte count) instead of raising #74) or supply a hand-written reader.
• Let users of the library register entries, since the list is file- and experiment-specific.

Severity / size: low, S–M once the mechanism exists.

Related: #9, #67, #71, #74.

Assisted-by: claude-code:claude-fable-5-1