From 7293402f6ac8644955f22423bad8bce2bdc166db Mon Sep 17 00:00:00 2001
From: Romain Ruetschi <romain@informal.systems>
Date: Wed, 15 May 2024 21:58:24 +0200
Subject: [PATCH] Add helper to deserialize into `Option` or `Result`

---
 src/de.rs          |  4 +--
 src/de/helpers.rs  | 64 +++++++++++++++++++++++++++++++++++++++++
 tests/sum_types.rs | 72 ++++++++++++++++++++++++++++++++++++++++++++--
 3 files changed, 136 insertions(+), 4 deletions(-)

diff --git a/src/de.rs b/src/de.rs
index dfc177e..ab5497e 100644
--- a/src/de.rs
+++ b/src/de.rs
@@ -6,12 +6,12 @@ mod error;
 pub use error::Error;
 
 mod helpers;
-pub use helpers::{As, Integer, Same};
+pub use helpers::{As, Integer, Option, Result, Same};
 
 mod deserializer;
 
 #[doc(hidden)]
-pub fn decode_value<T>(value: Value) -> Result<T, Error>
+pub fn decode_value<T>(value: Value) -> std::result::Result<T, Error>
 where
     T: DeserializeOwned,
 {
diff --git a/src/de/helpers.rs b/src/de/helpers.rs
index 1499c88..8280657 100644
--- a/src/de/helpers.rs
+++ b/src/de/helpers.rs
@@ -1,4 +1,5 @@
 use num_bigint::BigInt;
+use serde::{Deserialize, Serialize};
 
 pub use serde_with::{As, Same};
 
@@ -71,3 +72,66 @@ pub use serde_with::{As, Same};
 /// itf::from_value::<Vec<FooBarMixInt>>(json.clone()).unwrap();
 /// ```
 pub type Integer = serde_with::TryFromInto<BigInt>;
+
+/// Helper for `serde` to deserialize types isomorphic to [`std::option::Option`].
+///
+/// To be used in conjunction with [`As`].
+pub type Option<T> = serde_with::FromInto<QuintOption<T>>;
+
+#[derive(
+    Copy, Clone, Debug, Default, PartialEq, Eq, PartialOrd, Ord, Hash, Serialize, Deserialize,
+)]
+#[serde(tag = "tag", content = "value")]
+pub enum QuintOption<T> {
+    #[default]
+    None,
+    Some(T),
+}
+
+impl<T> From<std::option::Option<T>> for QuintOption<T> {
+    fn from(opt: std::option::Option<T>) -> Self {
+        match opt {
+            Some(value) => QuintOption::Some(value),
+            None => QuintOption::None,
+        }
+    }
+}
+
+impl<T> From<QuintOption<T>> for std::option::Option<T> {
+    fn from(opt: QuintOption<T>) -> Self {
+        match opt {
+            QuintOption::Some(value) => Some(value),
+            QuintOption::None => None,
+        }
+    }
+}
+
+/// Helper for `serde` to deserialize types isomorphic to [`std::result::Result`].
+///
+/// To be used in conjunction with [`As`].
+pub type Result<T, E> = serde_with::FromInto<QuintResult<T, E>>;
+
+#[derive(Copy, Clone, Debug, PartialEq, Eq, PartialOrd, Ord, Hash, Serialize, Deserialize)]
+#[serde(tag = "tag", content = "value")]
+pub enum QuintResult<T, E> {
+    Ok(T),
+    Err(E),
+}
+
+impl<T, E> From<std::result::Result<T, E>> for QuintResult<T, E> {
+    fn from(opt: std::result::Result<T, E>) -> Self {
+        match opt {
+            Ok(value) => QuintResult::Ok(value),
+            Err(e) => QuintResult::Err(e),
+        }
+    }
+}
+
+impl<T, E> From<QuintResult<T, E>> for std::result::Result<T, E> {
+    fn from(opt: QuintResult<T, E>) -> Self {
+        match opt {
+            QuintResult::Ok(value) => Ok(value),
+            QuintResult::Err(e) => Err(e),
+        }
+    }
+}
diff --git a/tests/sum_types.rs b/tests/sum_types.rs
index eb1b2bc..c9f4565 100644
--- a/tests/sum_types.rs
+++ b/tests/sum_types.rs
@@ -28,7 +28,7 @@ fn parse_trace() {
 }
 
 #[test]
-fn test_deserialize_some() {
+fn test_deserialize_adhoc_some() {
     let some_itf = json!({
         "tag": "Some",
         "value": {"#bigint": "1"},
@@ -39,7 +39,7 @@ fn test_deserialize_some() {
 }
 
 #[test]
-fn test_deserialize_none() {
+fn test_deserialize_adhoc_none() {
     let none_itf = json!({
         "tag": "None",
         "value": {},
@@ -93,3 +93,71 @@ fn test_deserialize_enum() {
     let foobar = itf::from_value::<Enum>(foobar_itf).unwrap();
     assert_eq!(foobar, Enum::FooBar("hello".to_string(), 42.into(), true));
 }
+
+#[derive(Debug, PartialEq, Deserialize)]
+struct FooOption {
+    #[serde(with = "As::<itf::de::Option::<_>>")]
+    foo: Option<u64>,
+}
+
+#[test]
+#[allow(clippy::disallowed_names)]
+fn test_deserialize_option_some() {
+    let some_itf = json!({
+        "foo": {
+            "tag": "Some",
+            "value": 42,
+        }
+    });
+
+    let some_foo = itf::from_value::<FooOption>(some_itf).unwrap();
+    assert_eq!(some_foo, FooOption { foo: Some(42) });
+}
+
+#[test]
+#[allow(clippy::disallowed_names)]
+fn test_deserialize_option_none() {
+    let none_itf = json!({
+        "foo": {
+            "tag": "None",
+            "value": {},
+        }
+    });
+
+    let none_foo = itf::from_value::<FooOption>(none_itf).unwrap();
+    assert_eq!(none_foo, FooOption { foo: None });
+}
+
+#[derive(Debug, PartialEq, Deserialize)]
+struct FooResult {
+    #[serde(with = "As::<itf::de::Result::<_, _>>")]
+    foo: Result<u64, u64>,
+}
+
+#[test]
+#[allow(clippy::disallowed_names)]
+fn test_deserialize_result_ok() {
+    let ok_itf = json!({
+        "foo": {
+            "tag": "Ok",
+            "value": 42,
+        }
+    });
+
+    let ok = itf::from_value::<FooResult>(ok_itf).unwrap();
+    assert_eq!(ok.foo, Ok(42));
+}
+
+#[test]
+#[allow(clippy::disallowed_names)]
+fn test_deserialize_result_err() {
+    let err_itf = json!({
+        "foo": {
+            "tag": "Err",
+            "value": 42,
+        }
+    });
+
+    let err = itf::from_value::<FooResult>(err_itf).unwrap();
+    assert_eq!(err.foo, Err(42));
+}