Features and MSRV

Cargo features, what each adds, TLS for PostgreSQL, and the MSRV policy.

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The features

All features are off by default. Without any, the crate is the rule core, both façades, MemoryStore, proofs, reports, the export view and every C2SP text format — no async runtime, no database driver, no signature library. The same list is rendered under "Feature flags" on the crate root.

Feature	Adds	Brings
`serde`	`Serialize` / `Deserialize` on all public types; the hashed encoding never goes through serde	`serde`
`sqlite`	`SqlStore<Sqlite>`, SQLite bundled	`sqlx` (tokio runtime)
`postgres`	`SqlStore<Postgres>`, no TLS stack	`sqlx` (tokio runtime)
`witness`	Ed25519: `LogKey` signs checkpoints; cosignatures and policies verify; `WitnessSession`, `Verifier`	`ed25519-dalek`
`testing`	`doubleentry::testing`: the conformance suite for stores (with `witness`, also `TestWitness`)	`tokio`
`tracing`	a span per façade operation and per SQL store write — never an amount, memo or account path	`tracing`

Always on: sha2, time, unicode-normalization (NFC for names), getrandom (memo salts), thiserror and document-features.

Without witness, notes, checkpoints, vkeys, policies, requests, bundles and tiles still parse and render, so a monitor that only reads checkpoints needs no Ed25519. The crate has no HTTP client and no witness: it builds add-checkpoint requests and reads replies as bytes.

TLS for PostgreSQL

sqlx is compiled without a TLS stack; the application picks one with one line, and Cargo's feature unification switches it on for the crate's connections:

[dependencies]
doubleentry = { version = "0.8", features = ["postgres"] }
sqlx = { version = "0.9", features = ["tls-rustls-aws-lc-rs"] }   # or tls-rustls-ring-webpki, tls-native-tls

The connection URL then asks for it, for example ?sslmode=require. SQLite never needs TLS.

Runtime

Ledger's methods are plain async fns. The SQL stores run on sqlx's tokio runtime, so SqlStore is used inside a tokio runtime — #[tokio::main] or one the program builds (With a database). Journal needs no runtime.

MSRV

Rust 1.94, edition 2024, set by rust-version in Cargo.toml and required by sqlx 0.9. CI builds every feature and target with exactly that toolchain and --locked. The MSRV is a stable release at least six months old when adopted, and rises only in a non-patch release, with a CHANGELOG line naming the reason.

Limits

tracing only emits spans; the subscriber is the application's.
testing::TestWitness is a test double; the crate ships no production witness.
The MSRV covers the locked dependencies; newer versions an application's own lock file picks may need a newer compiler.