Crate field_kinds 

Compile-time struct field introspection via derive macro.

This crate provides the FieldKinds derive macro that generates compile-time metadata about struct fields, including their names, types, categories, and custom tags.

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 to fields via #[field_tags("tag1", "tag2")]
• Static metadata: All field info available as const FIELDS: &'static [FieldMeta]
• Zero runtime cost: All metadata is computed at compile time

Example

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>,
}

// Get field names
assert_eq!(User::field_names(), vec!["user_id", "user_name", "is_active", "email"]);

// Get 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"]);

// 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"));

// Access static metadata directly
assert_eq!(User::FIELDS.len(), 4);

Attributes

Struct-level

• #[serde(rename_all = "...")] - Apply case conversion to serialized names

Field-level

• #[serde(rename = "...")] - Override serialized name for a field
• #[field_tags("tag1", "tag2")] - Add custom tags to a field
• #[field_kinds(skip)] - Skip a field from introspection

Structs

Bool

Marker type for boolean type.

Collection

Marker type for collection types (Vec, HashSet, HashMap, arrays, slices).

FieldMeta

Runtime-accessible metadata for a single field.

Numeric

Marker type for numeric types (i8-i128, u8-u128, f32, f64, isize, usize).

Optional

Marker type for optional types (Option<T>).

Text

Marker type for text types (String, &str, Box<str>, char).

Unknown

Marker type for types that don’t match any known category.

Traits

Categorized

Trait for mapping Rust types to their categories.

FieldCount

Trait for counting fields in an HList.

FieldInfo

Trait representing compile-time information about a struct field.

FieldKinds

Trait implemented by structs deriving FieldKinds.

FieldKindsExt

Extension trait providing convenient methods for field introspection.

HListVisitor

Marker trait for HLists of field types.

TypeCategory

Trait for type category markers.

VisitFields

Trait for types that provide static field metadata.

Derive Macros

FieldKinds