Crate serde_er7 

serde-er7

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Serde support for er7, the pipe-hat encoding that carries HL7 v2 messages between healthcare systems.

er7 parses, queries, edits, and writes ER7 text, deliberately with no dependencies of its own. This crate is the bridge from that value tree to the rest of the Serde ecosystem: wrap a parsed er7::Message in Message, and it can flow through serde_json, serde_yaml, bincode, or any other Serde data format — for storing a parsed message in a document database, logging it as structured JSON, returning it from a web API, or testing it with assert_eq! against a literal.

Every impl in this crate is written by hand against the low-level Serializer/Deserializer/Visitor traits, following the pattern serde’s own documentation walks through for a manual implementation — no #[derive(Serialize)] anywhere, because er7’s tree cannot derive its way to the shapes below (a bare array for a field’s repetitions, a bare string for a leaf) without help.

Example:

use serde_er7::Message;

let text = "MSH|^~\\&|LAB|ACME|EHR|CLINIC|20260815120000||ORU^R01|MSG9|P|2.5\r\
            PID|1||12345^^^ACME^MR||SMITH^JOHN^Q||19800101|M\r\
            OBX|1|NM|2093-3^Cholesterol^LN||187|mg/dL|||||F";

let message = Message::parse(text)?;

// Out to JSON, and back — this crate never mentions JSON itself; any
// Serde format works the same way.
let json = serde_json::to_string(&message)?;
let back: Message = serde_json::from_str(&json)?;

assert_eq!(back.to_er7(), text);

The shape each level serializes as

Level	Wrapper	Serializes as
Message	Message	object: {"separators": ..., "segments": [...]}
Segment	Segment	object: {"name": "PID", "fields": [...]}
Field	Field	array of repetitions
Repetition	Repetition	array of components
Component	Component	array of subcomponent strings
Subcomponent	Subcomponent	a bare string, raw (not er7::Subcomponent::value-decoded)
Separators	Separators	object of six named fields, chars as one-character strings
Terminator	Terminator	one of the strings "Cr", "Lf", "CrLf"

Every level below Message is optional to reach for directly — most callers only ever construct a Message and let its Serialize impl walk the rest of the tree. The lower levels are pub so a caller who only wants to serialize one segment, or one field, out of a larger message can do that too.

What is deliberately not here

This crate adds exactly one thing to er7: Serde support for its existing value tree. It does not add a dictionary, a validator, or a transport — er7 does not have those either, and a bridge crate is the wrong place to add what the crate it bridges declined to have. See er7’s own documentation for what “encoding, not dictionary” means in practice.

It also does not pick a wire format. serde_json appears only as a dev-dependency, to test and demonstrate against — the whole point of building against serde’s traits rather than writing an ER7-to-JSON converter directly is that the format is the caller’s choice, not this crate’s.

Documentation

spec/index.md in the repository is this crate’s specification — what each wrapper type must serialize as and why, following the same spec-driven process er7 itself uses. A tutorial is in docs/usage/index.md, and runnable programs are in examples/.

Re-exports

pub use er7;

Structs

Component

A Serde-enabled er7::Component.

Field

A Serde-enabled er7::Field.

Message

A Serde-enabled er7::Message — the crate’s main entry point.

Repetition

A Serde-enabled er7::Repetition.

Segment

A Serde-enabled er7::Segment.

Separators

A Serde-enabled er7::Separators.

Subcomponent

A Serde-enabled er7::Subcomponent.

Terminator

A Serde-enabled er7::Terminator.