Extractor rewrite

crates/pile-value/src/extract/item/sidecar.rs

@@ -0,0 +1,45 @@
+use pile_config::Label;
+use std::sync::OnceLock;
+
+use super::TomlExtractor;
+use crate::{
+	extract::traits::ObjectExtractor,
+	value::{Item, PileValue},
+};
+
+pub struct SidecarExtractor {
+	item: Item,
+	output: OnceLock<Option<TomlExtractor>>,
+}
+
+impl SidecarExtractor {
+	pub fn new(item: &Item) -> Self {
+		Self {
+			item: item.clone(),
+			output: OnceLock::new(),
+		}
+	}
+}
+
+#[async_trait::async_trait]
+impl ObjectExtractor for SidecarExtractor {
+	async fn field(&self, name: &Label) -> Result<Option<PileValue>, std::io::Error> {
+		match self
+			.output
+			.get_or_init(|| self.item.sidecar().map(TomlExtractor::new))
+		{
+			Some(x) => Ok(x.field(name).await?),
+			None => Ok(Some(PileValue::Null)),
+		}
+	}
+
+	async fn fields(&self) -> Result<Vec<Label>, std::io::Error> {
+		match self
+			.output
+			.get_or_init(|| self.item.sidecar().map(TomlExtractor::new))
+		{
+			Some(x) => Ok(x.fields().await?),
+			None => Ok(Vec::new()),
+		}
+	}
+}