bevy/crates/bevy_utils/src/short_names.rs

/// Shortens a type name to remove all module paths.
///
/// The short name of a type is its full name as returned by
/// [`std::any::type_name`], but with the prefix of all paths removed. For
/// example, the short name of `alloc::vec::Vec<core::option::Option<u32>>`
/// would be `Vec<Option<u32>>`.
pub fn get_short_name(full_name: &str) -> String {
    // Generics result in nested paths within <..> blocks.
    // Consider "bevy_render::camera::camera::extract_cameras<bevy_render::camera::bundle::Camera3d>".
    // To tackle this, we parse the string from left to right, collapsing as we go.
    let mut index: usize = 0;
    let end_of_string = full_name.len();
    let mut parsed_name = String::new();

    while index < end_of_string {
        let rest_of_string = full_name.get(index..end_of_string).unwrap_or_default();

        // Collapse everything up to the next special character,
        // then skip over it
        if let Some(special_character_index) = rest_of_string.find(|c: char| {
            (c == ' ')
                || (c == '<')
                || (c == '>')
                || (c == '(')
                || (c == ')')
                || (c == '[')
                || (c == ']')
                || (c == ',')
                || (c == ';')
        }) {
            let segment_to_collapse = rest_of_string
                .get(0..special_character_index)
                .unwrap_or_default();
            parsed_name += collapse_type_name(segment_to_collapse);
            // Insert the special character
            let special_character =
                &rest_of_string[special_character_index..=special_character_index];
            parsed_name.push_str(special_character);

            match special_character {
                ">" | ")" | "]"
                    if rest_of_string[special_character_index + 1..].starts_with("::") =>
                {
                    parsed_name.push_str("::");
                    // Move the index past the "::"
                    index += special_character_index + 3;
                }
                // Move the index just past the special character
                _ => index += special_character_index + 1,
            }
        } else {
            // If there are no special characters left, we're done!
            parsed_name += collapse_type_name(rest_of_string);
            index = end_of_string;
        }
    }
    parsed_name
}

#[inline(always)]
fn collapse_type_name(string: &str) -> &str {
    // Enums types are retained.
    // As heuristic, we assume the enum type to be uppercase.
    let mut segments = string.rsplit("::");
    let (last, second_last): (&str, Option<&str>) = (segments.next().unwrap(), segments.next());
    let Some(second_last) = second_last else {
        return last;
    };

    if second_last.starts_with(char::is_uppercase) {
        let index = string.len() - last.len() - second_last.len() - 2;
        &string[index..]
    } else {
        last
    }
}

#[cfg(test)]
mod name_formatting_tests {
    use super::get_short_name;

    #[test]
    fn trivial() {
        assert_eq!(get_short_name("test_system"), "test_system");
    }

    #[test]
    fn path_separated() {
        assert_eq!(
            get_short_name("bevy_prelude::make_fun_game"),
            "make_fun_game".to_string()
        );
    }

    #[test]
    fn tuple_type() {
        assert_eq!(
            get_short_name("(String, String)"),
            "(String, String)".to_string()
        );
    }

    #[test]
    fn array_type() {
        assert_eq!(get_short_name("[i32; 3]"), "[i32; 3]".to_string());
    }

    #[test]
    fn trivial_generics() {
        assert_eq!(get_short_name("a<B>"), "a<B>".to_string());
    }

    #[test]
    fn multiple_type_parameters() {
        assert_eq!(get_short_name("a<B, C>"), "a<B, C>".to_string());
    }

    #[test]
    fn enums() {
        assert_eq!(get_short_name("Option::None"), "Option::None".to_string());
        assert_eq!(
            get_short_name("Option::Some(2)"),
            "Option::Some(2)".to_string()
        );
        assert_eq!(
            get_short_name("bevy_render::RenderSet::Prepare"),
            "RenderSet::Prepare".to_string()
        );
    }

    #[test]
    fn generics() {
        assert_eq!(
            get_short_name("bevy_render::camera::camera::extract_cameras<bevy_render::camera::bundle::Camera3d>"),
            "extract_cameras<Camera3d>".to_string()
        );
    }

    #[test]
    fn nested_generics() {
        assert_eq!(
            get_short_name("bevy::mad_science::do_mad_science<mad_science::Test<mad_science::Tube>, bavy::TypeSystemAbuse>"),
            "do_mad_science<Test<Tube>, TypeSystemAbuse>".to_string()
        );
    }

    #[test]
    fn sub_path_after_closing_bracket() {
        assert_eq!(
            get_short_name("bevy_asset::assets::Assets<bevy_scene::dynamic_scene::DynamicScene>::asset_event_system"),
            "Assets<DynamicScene>::asset_event_system".to_string()
        );
        assert_eq!(
            get_short_name("(String, String)::default"),
            "(String, String)::default".to_string()
        );
        assert_eq!(
            get_short_name("[i32; 16]::default"),
            "[i32; 16]::default".to_string()
        );
    }
}