field-kinds

Compile-time struct field introspection for Rust.

Features

• Field names - Get field names as &'static str
• Serialized names - Supports #[serde(rename)] and #[serde(rename_all)]
• Type categories - Automatic categorization: numeric, text, bool, optional, collection
• Custom tags - Add arbitrary tags via #[field_tags("tag1", "tag2")]
• Static metadata - All field info available as const FIELDS: &'static [FieldMeta]
• Zero runtime cost - All metadata computed at compile time

Installation

[dependencies]
field-kinds = "0.2"

Quick Start

use field_kinds::{FieldKinds, FieldKindsExt, VisitFields};

#[derive(FieldKinds)]
#[serde(rename_all = "camelCase")]
struct User {
    user_id: u64,
    user_name: String,
    is_active: bool,
    #[field_tags("sensitive", "pii")]
    email: Option<String>,
}

fn main() {
    // Field names
    assert_eq!(User::field_names(), vec!["user_id", "user_name", "is_active", "email"]);
    
    // Serialized names (with rename_all applied)
    assert_eq!(User::serialized_names(), vec!["userId", "userName", "isActive", "email"]);
    
    // Filter by category
    assert_eq!(User::fields_by_category("numeric"), vec!["user_id"]);
    assert_eq!(User::fields_by_category("text"), vec!["user_name"]);
    assert_eq!(User::fields_by_category("optional"), vec!["email"]);
    
    // Filter by tag
    assert_eq!(User::fields_by_tag("sensitive"), vec!["email"]);
    
    // Check field existence
    assert!(User::has_field("user_id"));
    assert!(!User::has_field("nonexistent"));
    
    // Get field category
    assert_eq!(User::field_category("user_id"), Some("numeric"));
    
    // Access static metadata directly
    assert_eq!(User::FIELDS.len(), 4);
    
    // Iterate over field metadata
    for field in User::FIELDS {
        println!("{}: {} [{:?}]", field.name, field.category, field.tags);
    }
}

Attributes

Struct-level

Supported cases: camelCase, snake_case, PascalCase, SCREAMING_SNAKE_CASE, kebab-case

Field-level

Type Categories

Types are automatically categorized:

Custom Categories

Implement Categorized for your types:

use field_kinds::{Categorized, Numeric};

struct Money(i64);

impl Categorized for Money {
    type Category = Numeric;
}

MSRV

Minimum supported Rust version is 1.90.0 (Rust 2024 edition).

License

MIT