forgot to git add this

web3_proxy/src/frontend/axum_ext.rs

@@ -0,0 +1,18 @@
+use axum::{extract::Query, routing::get, Router};
+use serde::{de, Deserialize, Deserializer};
+use std::{fmt, str::FromStr};
+
+/// Serde deserialization decorator to map empty Strings to None,
+/// https://github.com/tokio-rs/axum/blob/1fe45583626a4c9c890cc01131d38c57f8728686/examples/query-params-with-empty-strings/src/main.rs
+pub fn empty_string_as_none<'de, D, T>(de: D) -> Result<Option<T>, D::Error>
+where
+    D: Deserializer<'de>,
+    T: FromStr,
+    T::Err: fmt::Display,
+{
+    let opt = Option::<String>::deserialize(de)?;
+    match opt.as_deref() {
+        None | Some("") => Ok(None),
+        Some(s) => FromStr::from_str(s).map_err(de::Error::custom).map(Some),
+    }
+}