# Changelog
## 0.1.2
### Added
- `pub const FIELD_COUNT: usize` emitted inside every per-version module,
carrying the field count of the family's main struct. Downstream parsers
can dispatch on the on-wire length without redeclaring the count
alongside the macro invocation.
- Auto-`impl From<v_prev::Struct> for v_curr::Struct` for every shared
struct on every `#[add]`-only hop. The codegen bridges family-internal
types across the version boundary (`.into()` for direct references,
`.map(Into::into)` for `Option<T>`, `.into_iter().map(Into::into).collect()`
for `Vec<T>`). Hops with `#[edit]` / `#[delete]` are deliberately skipped;
the user writes a manual `From` and the chain picks it up.
- `pub fn AnyVersion::into_latest(self) -> Latest` emitted when the main
struct's chain is fully auto-emittable from end to end. Walks the
auto-generated `From` impls one hop at a time, so v0.1 → v0.3 routes
through the intermediate v0.2 step.
- `#[add(default = <expr>)]` syntax. The expression is used verbatim to
populate the added field in the auto-`From` migration. Without the
attribute, the codegen falls back to `::core::default::Default::default()`
— so `Added` field types need `Default` (typically satisfied by adding
`Default` to the family `derive(...)` list).
### Notes
- Auto-`From` for a struct is only emitted when every family struct it
transitively references is also auto-emittable on the same hop (computed
by a fixed-point pass). This guarantees the carried `.into()` calls
never dangle.
- The `into_latest` emission is gated on the *main* struct's entire chain
being clean. If any hop has a `#[edit]` / `#[delete]` on the main
struct, `into_latest` is not emitted and the user writes their own.
## 0.1.1
### Added
- `codec` clause in the `versioned!` DSL. Accepts any subset of `rkyv`,
`bincode`, `postcard` (e.g. `codec rkyv, bincode;`).
- Per-codec dispatcher functions emitted at the family level:
`parse_at_version_rkyv(version, &[u8])`,
`parse_at_version_bincode(version, &[u8])`,
`parse_at_version_postcard(version, &[u8])`.
- Per-codec serializer methods on `AnyVersion`: `to_rkyv_bytes`,
`to_bincode_bytes`, `to_postcard_bytes`.
- Cargo features `rkyv-08`, `rkyv-07`, `bincode-2`, `postcard-1` on the
`polyvers` crate. They pass through to `polyvers-macros` and gate the
codegen for each codec. Using `codec X;` without the matching feature
produces a clear compile-time error.
- `polyvers::Error::format_str(impl Into<String>)` for wrapping codec errors
whose type does not implement `std::error::Error` (some `rkyv` 0.7 paths).
- `examples/codec_rkyv.rs` runnable example.
### Notes
- The JSON `parse_at_version` dispatcher is still always emitted. A family
that declares any codec must therefore also derive
`serde::{Serialize, Deserialize}`. Future work: opt-out via `codec json;`
so binary-only families can drop serde derives.
- `rkyv-08` and `rkyv-07` are mutually exclusive — enable at most one.
## 0.1.0
Initial release. Single-macro schema versioning via `polyvers::versioned!`:
- `#[add]` / `#[edit]` / `#[delete]` field mutations across `version "…"`
blocks, with implicit struct inheritance.
- One self-contained module emitted per declared version (`v0_1`, `v0_2`, …),
so sub-struct types resolve to the correct version automatically — no
`serde(flatten)` overhead.
- `Latest` type alias, `VERSIONS`/`LATEST_VERSION` constants, `AnyVersion`
enum with `version()`/`into_vX_Y()`/`as_vX_Y()` helpers.
- `parse_at_version(version, &str) -> Result<AnyVersion, Error>` for runtime
JSON dispatch.
- Per-version metadata via a `meta TypeName;` clause + `meta { … }` blocks,
exposed as `vX_Y::meta()`, `meta_at_version(&str)`, and `AnyVersion::meta()`.
- Field-level attributes (e.g. `#[serde(rename = "…")]`) forwarded and
inherited across versions.
