Crate qubit_metadata 

qubit-metadata

A general-purpose, type-safe, extensible metadata model for Rust.

This crate provides a Metadata type — a structured key-value store designed for any domain that needs to attach arbitrary, typed, serializable annotations to its data models. It is not a plain HashMap — it is a structured extensibility point with type-safe access, serde_json::Value backing, and first-class serde support.

Design Goals

• Type Safety: Typed get/set API backed by serde_json::Value
• Generality: No domain-specific assumptions — usable in any Rust project
• Extensibility: Acts as a structured extension point, not a stringly-typed bag
• Serialization: First-class serde support for JSON interchange
• Filtering: MetadataFilter for composable query conditions

Features

• Core type: Metadata — an ordered key-value store with typed accessors
• Filter type: MetadataFilter — composable filter expressions for metadata queries
• Condition type: Condition — individual comparison predicates
• Error type: MetadataError — explicit failure reporting for try_* APIs
• Type inspection: MetadataValueKind — lightweight JSON kind inspection

Example

use qubit_metadata::{Metadata, MetadataFilter};

let mut meta = Metadata::new();
meta.set("author", "alice");
meta.set("priority", 3_i64);

// Convenience API: missing key and type mismatch both collapse to None.
let author: Option<String> = meta.get("author");
assert_eq!(author.as_deref(), Some("alice"));

// Explicit API: preserve failure reasons for diagnostics.
let priority = meta.try_get::<i64>("priority").unwrap();
assert_eq!(priority, 3);

let filter = MetadataFilter::eq("author", "alice")
    .and(MetadataFilter::gte("priority", 1_i64));
assert!(filter.matches(&meta));

Author

Haixing Hu

Structs

Metadata

A structured, ordered, type-safe key-value store for attaching arbitrary annotations to domain objects.

Enums

Condition

A single comparison operator applied to one metadata key.

MetadataError

Errors produced by explicit Metadata accessors such as Metadata::try_get and Metadata::try_set.

MetadataFilter

A composable filter expression over Metadata.

MetadataValueKind

Coarse-grained JSON value kinds used by MetadataError and inspection APIs.

Type Aliases

MetadataResult

Result type used by explicit Metadata operations that report failure reasons instead of collapsing them into None.