lofty_attr 0.11.1

Macros for Lofty
Documentation 
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use syn::parse::Parse;
use syn::punctuated::Punctuated;
use syn::{token, Attribute, Expr, Ident, LitStr, Token};

pub(crate) enum AttributeValue {
	/// `#[lofty(attribute_name)]`
	Path(Ident),
	/// `#[lofty(attribute_name = "value")]`
	NameValue(Ident, LitStr),
	#[allow(dead_code)]
	/// `#[lofty(attribute_name(value1, value2, value3))]`
	SingleList(Ident, Punctuated<Expr, Token![,]>),
}

impl AttributeValue {
	pub(crate) fn from_attribute(
		expected_path: &str,
		attribute: &Attribute,
	) -> syn::Result<Option<Self>> {
		if !attribute.path().is_ident(expected_path) {
			return Ok(None);
		}

		let mut value = None;
		attribute.parse_nested_meta(|meta| {
			// `#[lofty(attribute_name)]`
			if meta.input.is_empty() {
				value = Some(AttributeValue::Path(meta.path.get_ident().unwrap().clone()));
				return Ok(());
			}

			// `#[lofty(attribute_name = "value")]`
			if meta.input.peek(token::Eq) {
				let val = meta.value()?;
				let str_value: LitStr = val.parse()?;

				value = Some(AttributeValue::NameValue(
					meta.path.get_ident().unwrap().clone(),
					str_value,
				));
				return Ok(());
			}

			// `#[lofty(attribute_name(value1, value2, value3))]`
			if meta.input.peek(token::Paren) {
				return meta.parse_nested_meta(|meta| {
					let list = meta.input.parse_terminated(syn::Expr::parse, Token![,])?;
					value = Some(AttributeValue::SingleList(
						meta.path.get_ident().unwrap().clone(),
						list,
					));

					Ok(())
				});
			}

			Err(meta.error("Unrecognized attribute format"))
		})?;

		Ok(value)
	}
}