humantime_serde_option: New module in tor-basic-utils

This will be used to allow our config *builder* structs to be
Deserialize.

Cargo.lock

@@ -3098,6 +3098,8 @@ name = "tor-basic-utils"
 version = "0.1.0"
 dependencies = [
  "educe",
+ "humantime-serde",
+ "serde",
 ]
 
 [[package]]

crates/tor-basic-utils/Cargo.toml

@@ -11,6 +11,12 @@ categories = ["rust-patterns"] # We must put *something* here and this will do
 repository = "https://gitlab.torproject.org/tpo/core/arti.git/"
 
 [dependencies]
+serde = { version = "1.0.103", features = ["derive"], optional = true }
+humantime-serde-crate = { package = "humantime-serde", version = "1", optional = true }
+
+[features]
+default = ["humantime-serde"]
+humantime-serde = ["humantime-serde-crate", "serde"]
 
 [dev-dependencies]
 educe = "0.4.6"

crates/tor-basic-utils/src/humantime_serde_option.rs

@@ -0,0 +1,24 @@
+//! Module to adaopt `humantime_serde` to `Option<Duration>`
+
+use humantime_serde_crate::Serde as HtSerde;
+use serde::{Deserialize, Deserializer, Serialize, Serializer};
+
+/// Serializes an `Option<Duration>` or `Option<SystemTime>` via the humantime crate.
+pub fn serialize<T, S>(d: &Option<T>, s: S) -> Result<S::Ok, S::Error>
+where
+    for<'a> HtSerde<&'a T>: Serialize,
+    S: Serializer,
+{
+    let nested: Option<HtSerde<&T>> = d.as_ref().map(Into::into);
+    nested.serialize(s)
+}
+
+/// Deserialize an `Option<Duration>` or `Option<SystemTime>` via the humantime crate.
+pub fn deserialize<'a, T, D>(d: D) -> Result<Option<T>, D::Error>
+where
+    HtSerde<T>: Deserialize<'a>,
+    D: Deserializer<'a>,
+{
+    let got: Option<HtSerde<T>> = Deserialize::deserialize(d)?;
+    Ok(got.map(HtSerde::into_inner))
+}

crates/tor-basic-utils/src/lib.rs

@@ -41,6 +41,9 @@
 
 use std::fmt;
 
+#[cfg(feature = "humantime-serde")]
+pub mod humantime_serde_option;
+
 // ----------------------------------------------------------------------
 
 /// Function with the signature of `Debug::fmt` that just prints `".."`