field-meta

A Rust procedural macro that provides compile-time field metadata access for structs.

Overview

field-meta is a derive macro that automatically generates methods to introspect struct fields at compile time. It allows you to:

• Get a list of all field names in a struct
• Check if a field exists by name
• Count the number of fields
• Optionally skip fields from being included in metadata

Installation

Add this to your Cargo.toml:

[dependencies]
field-meta = "0.1.1"

Usage

Basic Example

use field_meta::FieldMeta;

#[derive(FieldMeta)]
struct User {
    id: u64,
    name: String,
    email: String,
    age: Option<u32>,
}

fn main() {
    // Get all field names
    let fields = User::fields();
    assert_eq!(fields, &["id", "name", "email", "age"]);

    // Check if a field exists
    assert!(User::contains_field("name"));
    assert!(!User::contains_field("password"));

    // Get field count
    assert_eq!(User::field_count(), 4);
}

Skipping Fields

You can exclude fields from the metadata using the #[field_meta(skip)] attribute:

use field_meta::FieldMeta;

#[derive(FieldMeta)]
struct Config {
    public_key: String,
    #[field_meta(skip)]
    private_key: String,  // This field won't be included in metadata
    timeout: u64,
}

fn main() {
    let fields = Config::fields();
    assert_eq!(fields, &["public_key", "timeout"]);

    assert!(!Config::contains_field("private_key"));
    assert_eq!(Config::field_count(), 2);
}

Field Aliases

Use #[field_meta(alias = "...")] to create an alias that contains_field() will recognize:

use field_meta::FieldMeta;

#[derive(FieldMeta)]
struct Person {
    #[field_meta(alias = "username")]
    name: String,
    email: String,
}

fn main() {
    // Both the original name and alias work
    assert!(Person::contains_field("name"));
    assert!(Person::contains_field("username"));
}

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

License

This project is licensed under the MIT License - see the LICENSE file for details.