1 files changed, 79 insertions, 0 deletions
diff --git a/vendor/darling-0.14.4/examples/shorthand_or_long_field.rs b/vendor/darling-0.14.4/examples/shorthand_or_long_field.rs
new file mode 100644
index 000000000..750d83efb
--- /dev/null
+++ b/vendor/darling-0.14.4/examples/shorthand_or_long_field.rs
@@ -0,0 +1,79 @@
+//! Example showing potentially-nested meta item parsing with `darling::util::Override`.
+//!
+//! Based on https://stackoverflow.com/q/68046070/86381 by https://github.com/peterjoel
+
+// The use of fields in debug print commands does not count as "used",
+// which causes the fields to trigger an unwanted dead code warning.
+#![allow(dead_code)]
+
+use std::borrow::Cow;
+
+use darling::{util::Override, FromDeriveInput, FromMeta};
+use syn::{Ident, Path};
+
+#[derive(Debug, FromDeriveInput)]
+#[darling(attributes(myderive))]
+struct MyDeriveInput {
+    ident: Ident,
+    /// We can infer the right "table" behavior for this derive, but we want the caller to be
+    /// explicit that they're expecting the inference behavior to avoid cluttering some hypothetical
+    /// database. Therefore this field is required, but can take word form or key-value form.
+    ///
+    /// To make this field optional, we could add `#[darling(default)]`, or we could
+    /// wrap it in `Option` if the presence or absence of the word makes a difference.
+    table: Override<Table>,
+}
+
+impl MyDeriveInput {
+    fn table(&self) -> Cow<'_, Table> {
+        match &self.table {
+            Override::Explicit(value) => Cow::Borrowed(value),
+            Override::Inherit => Cow::Owned(Table {
+                name: self.ident.to_string(),
+                value: None,
+            }),
+        }
+    }
+}
+
+#[derive(Debug, Clone, FromMeta)]
+struct Table {
+    name: String,
+    value: Option<Path>,
+}
+
+fn from_str(s: &str) -> darling::Result<MyDeriveInput> {
+    FromDeriveInput::from_derive_input(&syn::parse_str(s)?)
+}
+
+fn main() {
+    let missing = from_str(
+        r#"
+        #[derive(MyTrait)]
+        struct Foo(u64);
+    "#,
+    )
+    .unwrap_err();
+
+    let short_form = from_str(
+        r#"
+        #[derive(MyTrait)]
+        #[myderive(table)]
+        struct Foo(u64);
+    "#,
+    )
+    .unwrap();
+
+    let long_form = from_str(
+        r#"
+        #[derive(MyTrait)]
+        #[myderive(table(name = "Custom"))]
+        struct Foo(u64);
+    "#,
+    )
+    .unwrap();
+
+    println!("Error when missing: {}", missing);
+    println!("Short form: {:?}", short_form.table());
+    println!("Long form: {:?}", long_form.table());
+}