Make Option<T> work with contracttype (#1145)

### What
Try to make Option<T> work with contracttype

### Why
Close stellar/rs-soroban-env#444
Close #877

Dependent on:
- stellar/rs-stellar-xdr#320
- stellar/rs-soroban-env#1198

Cargo.toml

@@ -42,25 +42,25 @@ soroban-token-sdk = { version = "20.0.0-rc2", path = "soroban-token-sdk" }
 [workspace.dependencies.soroban-env-common]
 version = "20.0.0-rc2"
 git = "https://github.com/stellar/rs-soroban-env"
-rev = "472486c9dba96e09746522df0c9052cd50568e62"
+rev = "d587d082d6b0d82f04730c9a67ac03ed9cc21dd6"
 
 [workspace.dependencies.soroban-env-guest]
 version = "20.0.0-rc2"
 git = "https://github.com/stellar/rs-soroban-env"
-rev = "472486c9dba96e09746522df0c9052cd50568e62"
+rev = "d587d082d6b0d82f04730c9a67ac03ed9cc21dd6"
 
 [workspace.dependencies.soroban-env-host]
 version = "20.0.0-rc2"
 git = "https://github.com/stellar/rs-soroban-env"
-rev = "472486c9dba96e09746522df0c9052cd50568e62"
+rev = "d587d082d6b0d82f04730c9a67ac03ed9cc21dd6"
 
 [workspace.dependencies.stellar-strkey]
 version = "0.0.8"
 
 [workspace.dependencies.stellar-xdr]
 version = "20.0.0-rc1"
 git = "https://github.com/stellar/rs-stellar-xdr"
-rev = "957273d7b8092888849219a3ad2aa054059ca89d"
+rev = "d6f8ece2c89809d5e2800b9df64ae60787ee492b"
 default-features = false
 features = ["curr"]
 

soroban-sdk/src/tests.rs

@@ -11,6 +11,7 @@ mod contract_overlapping_type_fn_names;
 mod contract_snapshot;
 mod contract_store;
 mod contract_udt_enum;
+mod contract_udt_option;
 mod contract_udt_struct;
 mod contract_udt_struct_tuple;
 mod contractimport;

soroban-sdk/src/tests/contract_udt_option.rs

@@ -0,0 +1,30 @@
+use crate as soroban_sdk;
+use soroban_sdk::{contract, contractimpl, contracttype, Env};
+
+#[derive(Copy, Clone, Debug, Eq, PartialEq)]
+#[contracttype]
+pub struct Udt {
+    pub a: i32,
+    pub b: Option<i32>,
+}
+
+#[contract]
+pub struct Contract;
+
+#[contractimpl]
+impl Contract {
+    pub fn add(a: Udt, b: Udt) -> (Udt, Udt) {
+        (a, b)
+    }
+}
+
+#[test]
+fn test_functional() {
+    let env = Env::default();
+    let contract_id = env.register_contract(None, Contract);
+
+    let a = Udt { a: 5, b: None };
+    let b = Udt { a: 10, b: Some(1) };
+    let c = ContractClient::new(&env, &contract_id).add(&a, &b);
+    assert_eq!(c, (a, b));
+}

soroban-sdk/src/testutils/arbitrary.rs

@@ -317,19 +317,53 @@ mod objects {
     use super::composite::ArbitraryVal;
     use crate::env::FromVal;
     use crate::ConversionError;
-    use crate::{Env, IntoVal, TryFromVal};
+    use crate::{Env, IntoVal, TryFromVal, TryIntoVal};
 
     use crate::xdr::{Int256Parts, ScVal, UInt256Parts};
     use crate::{
         Address, Bytes, BytesN, Duration, Map, String, Symbol, Timepoint, Val, Vec, I256, U256,
     };
-    use soroban_env_host::TryIntoVal;
 
     use std::string::String as RustString;
     use std::vec::Vec as RustVec;
 
     //////////////////////////////////
 
+    #[derive(Arbitrary, Debug, Clone, Eq, PartialEq, Ord, PartialOrd)]
+    pub struct ArbitraryOption<T>(Option<T>);
+
+    impl<T> SorobanArbitrary for Option<T>
+    where
+        T: SorobanArbitrary,
+        Val: TryFromVal<Env, T::Prototype>,
+        Val: TryFromVal<Env, T>,
+        <T as TryFromVal<Env, Val>>::Error:
+            From<<Val as TryFromVal<Env, <T as SorobanArbitrary>::Prototype>>::Error>,
+    {
+        type Prototype = ArbitraryOption<T::Prototype>;
+    }
+
+    impl<T> TryFromVal<Env, ArbitraryOption<T::Prototype>> for Option<T>
+    where
+        T: SorobanArbitrary,
+        Val: TryFromVal<Env, T::Prototype>,
+        <T as TryFromVal<Env, Val>>::Error:
+            From<<Val as TryFromVal<Env, <T as SorobanArbitrary>::Prototype>>::Error>,
+    {
+        type Error = <T as TryFromVal<Env, Val>>::Error;
+        fn try_from_val(env: &Env, v: &ArbitraryOption<T::Prototype>) -> Result<Self, Self::Error> {
+            match v.0 {
+                Some(ref t) => {
+                    let v = Val::try_from_val(env, t)?;
+                    v.try_into_val(env)
+                }
+                None => Ok(None),
+            }
+        }
+    }
+
+    //////////////////////////////////
+
     #[derive(Arbitrary, Debug, Clone, Eq, PartialEq, Ord, PartialOrd)]
     pub struct ArbitraryU256 {
         parts: (u64, u64, u64, u64),