1 files changed, 77 insertions, 0 deletions
diff --git a/third_party/rust/serde_with_macros/src/utils.rs b/third_party/rust/serde_with_macros/src/utils.rs
new file mode 100644
index 0000000000..068cbce6ed
--- /dev/null
+++ b/third_party/rust/serde_with_macros/src/utils.rs
@@ -0,0 +1,77 @@
+use core::iter::Iterator;
+use darling::FromDeriveInput;
+use proc_macro::TokenStream;
+use proc_macro2::TokenStream as TokenStream2;
+use quote::ToTokens;
+use syn::{parse_quote, Error, Generics, Path, TypeGenerics};
+
+/// Merge multiple [`syn::Error`] into one.
+pub(crate) trait IteratorExt {
+    fn collect_error(self) -> Result<(), Error>
+    where
+        Self: Iterator<Item = Result<(), Error>> + Sized,
+    {
+        let accu = Ok(());
+        self.fold(accu, |accu, error| match (accu, error) {
+            (Ok(()), error) => error,
+            (accu, Ok(())) => accu,
+            (Err(mut err), Err(error)) => {
+                err.combine(error);
+                Err(err)
+            }
+        })
+    }
+}
+impl<I> IteratorExt for I where I: Iterator<Item = Result<(), Error>> + Sized {}
+
+/// Attributes usable for derive macros
+#[derive(FromDeriveInput)]
+#[darling(attributes(serde_with))]
+pub(crate) struct DeriveOptions {
+    /// Path to the crate
+    #[darling(rename = "crate", default)]
+    pub(crate) alt_crate_path: Option<Path>,
+}
+
+impl DeriveOptions {
+    pub(crate) fn from_derive_input(input: &syn::DeriveInput) -> Result<Self, TokenStream> {
+        match <Self as FromDeriveInput>::from_derive_input(input) {
+            Ok(v) => Ok(v),
+            Err(e) => Err(TokenStream::from(e.write_errors())),
+        }
+    }
+
+    pub(crate) fn get_serde_with_path(&self) -> Path {
+        self.alt_crate_path
+            .clone()
+            .unwrap_or_else(|| syn::parse_str("::serde_with").unwrap())
+    }
+}
+
+// Inspired by https://github.com/serde-rs/serde/blob/fb2fe409c8f7ad6c95e3096e5e9ede865c8cfb49/serde_derive/src/de.rs#L3120
+// Serde is also licensed Apache 2 + MIT
+pub(crate) fn split_with_de_lifetime(
+    generics: &Generics,
+) -> (
+    DeImplGenerics<'_>,
+    TypeGenerics<'_>,
+    Option<&syn::WhereClause>,
+) {
+    let de_impl_generics = DeImplGenerics(generics);
+    let (_, ty_generics, where_clause) = generics.split_for_impl();
+    (de_impl_generics, ty_generics, where_clause)
+}
+
+pub(crate) struct DeImplGenerics<'a>(&'a Generics);
+
+impl<'a> ToTokens for DeImplGenerics<'a> {
+    fn to_tokens(&self, tokens: &mut TokenStream2) {
+        let mut generics = self.0.clone();
+        generics.params = Some(parse_quote!('de))
+            .into_iter()
+            .chain(generics.params)
+            .collect();
+        let (impl_generics, _, _) = generics.split_for_impl();
+        impl_generics.to_tokens(tokens);
+    }
+}