serde-hl7

What it is

The shape of the `hl7` umbrella, one layer up: `serde_hl7::v2` is the `serde-hl7-v2` crate and `serde_hl7::v3` is `serde-hl7-v3`, each behind a Cargo feature of the same name, both on by default. Nothing lives at the root, for the same reason nothing lives at the root of `hl7`.

// serde-hl7/src/lib.rs, in full, minus the documentation
#[cfg(feature = "v2")]
pub use serde_hl7_v2 as v2;

#[cfg(feature = "v3")]
pub use serde_hl7_v3 as v3;

That is the entire crate. The hl7 crate organizes HL7 by standard because a “message” or a “code” in one standard is a different thing in another; this crate is the same shape one layer up, so a caller can depend on “Serde for HL7” and reach the standard they need by module.

Cargo features

cargo add serde-hl7                                          # v2 and v3
cargo add serde-hl7 --no-default-features --features v2      # v2 only

v2 and v3 are both on by default, mirroring hl7, which always carries both modules. Turn one off to skip the other's dependency tree entirely; a build with neither is an empty crate, which is allowed and useless.

Use

use serde_hl7::v2;

let text = "MSH|^~\\&|LAB||EPIC||20240101||ORU^R01|1|P|2.5\r\
            PID|1||241900||SMITH^JOHN";
let message = v2::Message::parse(text)?;

let json = serde_json::to_string(&message)?;
let back: v2::Message = serde_json::from_str(&json)?;
assert_eq!(back.to_er7(), text);

Any Serde format works the same way — serde_json is used here only because JSON is the easiest format to read on a page. Neither this crate nor the modules beneath it name a format in their runtime dependencies.

The modules

serde_hl7::v2 wraps hl7-2: the message (as its ER7 text plus the release it was read as), the dictionary-named tree, validation findings, and the release. serde_hl7::v3 wraps hl7-3: the three-level envelope, the six RIM backbone classes, the data types, and the raw XML element tree. Each is its own crate with its own normative spec.

What both modules share

Exactly two runtime dependencies each, serde and the hl7-* crate wrapped. Every Serialize/Deserialize impl hand-written against Serde's low-level traits, no derive, no proc-macro crate. A same-named wrapper per type that Derefs to the type it wraps, so the wrapped crate's whole API is reachable on the wrapper. Unknown keys ignored by default, and an opt-in Strict<T> that rejects them — the pattern serde-er7 established over er7.

Related crates