`ordered-float` v5 and the vendored `feldera-size-of` fork

Lille's DBSP records store floating-point values through ordered_float::OrderedFloat<f64> so that they have a total order, which DBSP requires for keys, joins, and aggregations. Those records also derive feldera_size_of::SizeOf for memory accounting. Reconciling the two across a major ordered-float upgrade is the reason for the arrangement described here.

For the full decision record, see ADR 002. The fork itself is documented in third_party/README.md. Fork lifecycle and removal are tracked in issue #294.

The workspace standardizes on ordered-float 5.x (ordered-float = { version = "5", features = ["serde", "rkyv_64"] } in the root Cargo.toml). This is the current major version, and Lille's own records are built against it. The rkyv_64 feature still targets rkyv 0.7, matching Lille's rkyv = "0.7", so the upgrade needs no rkyv changes.

Note that dbsp 0.98 independently requires ordered-float ^4.2.0, so ordered-float 4.x and 5.x coexist in the dependency graph: dbsp resolves to v4 for its own internals, while Lille's records use v5. This is expected and supported.

Every published feldera-size-of release, up to and including 0.1.7 (and upstream main), pins its optional ordered-float dependency at ^3.0.0. Its SizeOf impl for OrderedFloat/NotNan therefore applies only to ordered-float 3.x. Against 5.x the derive fails to compile:

error[E0277]: the trait bound `ordered_float::OrderedFloat<f64>:
feldera_size_of::SizeOf` is not satisfied

Lille cannot implement SizeOf for OrderedFloat itself, because both the trait and the type are foreign (the orphan rule forbids it). No upstream release accepts ordered-float 5.x, so there is nothing to upgrade to.

The workaround redirects the crate to a minimal vendored fork:

[patch.crates-io]
feldera-size-of = { path = "third_party/feldera-size-of" }

The fork widens its ordered-float constraint to 5 and switches the SizeOf impl bound from Float to FloatCore (ordered-float 5.x bounds its Deref impls on FloatCore, and the impl relies on the &OrderedFloat<T> → &T deref coercion). That bound switch is the only source change the upgrade requires.

[workspace]
members = ["build_support", "test_utils"]
exclude = ["third_party/feldera-size-of"]

The fork is a [patch.crates-io] target, not a first-class workspace member. Excluding it keeps Cargo from folding it into this workspace and keeps its upstream source out of the workspace-wide gates (cargo fmt, cargo clippy, cargo test, cargo doc). It is still built and linked, but only as a patched dependency of lille.

third_party/feldera-size-of is carried upstream code, not adopted or maintained Lille code. Except for the deliberately minimal changes listed in third_party/README.md, its source is byte-identical to feldera-size-of 0.1.7, and Lille does not hold it to this repository's code-health, testing, documentation, or lint standards. This is why the crate carries #![allow(warnings)] and #![cfg_attr(coverage_nightly, coverage(off))], and why .codescene/code-health-rules.json disables the Code Duplication rule under third_party/**.

Feedback about the upstream code that is outside the scope of the vendored fix — for example requests to test, refactor, or re-architect functionality Lille does not use, or to change the fork's fallible SizeOf traversal semantics or lint allowances — is out of scope for this repository. Raise such concerns upstream against feldera/size-of.

The Lille-owned guard for this arrangement is tests/ordered_float_size_of.rs, a compile-time integration regression test asserting that OrderedFloat<f64>, NotNan<f64>, Position, and BlockSlope implement SizeOf. It is Lille code and is maintained normally.

Once feldera-size-of publishes a release whose optional ordered-float dependency accepts 5.x (ideally including the Float → FloatCore bound fix):

1. Bump Lille's feldera-size-of dependency to that upstream release.
2. Delete third_party/feldera-size-of/.
3. Drop the [patch.crates-io] entry and the [workspace] exclude line from the root Cargo.toml.
4. Remove the CodeScene third_party/** rule set from .codescene/code-health-rules.json if nothing else needs it.
5. Keep tests/ordered_float_size_of.rs as the regression guard.
6. Regenerate Cargo.lock and run the standard gates.

Progress against these steps is tracked in issue #294.