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 typed annotations to its data models. It is not a plain HashMap — it is a structured extensibility point with type-safe access, qubit_value::Value backing, and first-class serde support.

Design Goals

• Type Safety: Typed get/set API backed by qubit_value::Value
• Generality: No domain-specific assumptions — usable in any Rust project
• Schema Support: Optional MetadataSchema validation for metadata and filters
• 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
• Schema type: MetadataSchema — field definitions based on qubit_common::DataType
• Filter type: MetadataFilter — composable filter expressions for metadata queries
• Condition type: Condition — individual comparison predicates
• Error type: MetadataError — explicit failure reporting for try_* APIs

Example

use qubit_metadata::{Metadata, MetadataFilter};

let meta = Metadata::new()
    .with("author", "alice")
    .with("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::builder()
    .eq("author", "alice")
    .and_ge("priority", 1_i64)
    .build()
    .unwrap();
assert!(filter.matches(&meta));

Author

Haixing Hu

Structs

FilterMatchOptions

Match policies used when evaluating a crate::MetadataFilter.

Metadata

A structured, ordered, typed key-value store for metadata fields.

MetadataField

Definition of one metadata field in a crate::MetadataSchema.

MetadataFilter

An immutable, composable filter expression over Metadata.

MetadataFilterBuilder

Builder for MetadataFilter.

MetadataSchema

Schema for metadata fields.

MetadataSchemaBuilder

Builder for MetadataSchema.

Enums

Condition

A single comparison operator applied to one metadata key.

MetadataError

Errors produced by explicit metadata accessors and schema validation.

MissingKeyPolicy

Policy that controls how filters treat missing keys for negative predicates.

NumberComparisonPolicy

Policy that controls mixed integer/float number comparisons.

UnknownFieldPolicy

Policy for fields that appear in metadata but are not declared by a schema.

Type Aliases

MetadataResult

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