From b781fe67532629f21ae52168bad8a5e4675d337d Mon Sep 17 00:00:00 2001
From: Gav Wood <gav@ethcore.io>
Date: Thu, 14 Jan 2016 23:13:28 +0100
Subject: [PATCH 1/2] from_existing works for an empty DB if passed empty RLP
 SHA3.

---
 src/trie/triedbmut.rs | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/src/trie/triedbmut.rs b/src/trie/triedbmut.rs
index 03d2b59de..d205dc8e0 100644
--- a/src/trie/triedbmut.rs
+++ b/src/trie/triedbmut.rs
@@ -71,6 +71,9 @@ impl<'db> TrieDBMut<'db> {
 	/// Create a new trie with the backing database `db` and `root`
 	/// Panics, if `root` does not exist
 	pub fn from_existing(db: &'db mut HashDB, root: &'db mut H256) -> Self {
+		if !db.exists(root) && root == &SHA3_NULL_RLP {
+			*root = db.insert(&NULL_RLP); 
+		}
 		assert!(db.exists(root));
 		TrieDBMut { 
 			db: db, 

From 6a7c823862d557f8994ad62a1d5cacbd42b66d0a Mon Sep 17 00:00:00 2001
From: Gav Wood <gav@ethcore.io>
Date: Thu, 14 Jan 2016 23:39:59 +0100
Subject: [PATCH 2/2] Option types in JSON, more tests.

---
 src/hash.rs     |  1 +
 src/json_aid.rs | 38 ++++++++++++++++++++++++++++++++++++--
 2 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/src/hash.rs b/src/hash.rs
index 8c1772b2c..c17b706db 100644
--- a/src/hash.rs
+++ b/src/hash.rs
@@ -195,6 +195,7 @@ macro_rules! impl_hash {
 			fn from_json(json: &Json) -> Self {
 				match json {
 					&Json::String(ref s) => {
+						println!("s: {}", s);
 						match s.len() % 2 {
 							0 => FromStr::from_str(clean_0x(s)).unwrap(),
 							_ => FromStr::from_str(&("0".to_string() + &(clean_0x(s).to_string()))[..]).unwrap()
diff --git a/src/json_aid.rs b/src/json_aid.rs
index e25e9406d..79a71cac6 100644
--- a/src/json_aid.rs
+++ b/src/json_aid.rs
@@ -46,6 +46,16 @@ impl<T> FromJson for Vec<T> where T: FromJson {
 	}
 }
 
+impl<T> FromJson for Option<T> where T: FromJson {
+	fn from_json(json: &Json) -> Self {
+		match json {
+			&Json::String(ref o) if o.is_empty() => None,
+			&Json::Null => None,
+			_ => Some(FromJson::from_json(json)),
+		}
+	}
+}
+
 impl FromJson for u64 {
 	fn from_json(json: &Json) -> Self {
 		U256::from_json(json).low_u64()
@@ -77,7 +87,7 @@ fn u256_from_json() {
 }
 
 #[test]
-fn h256_from_json_() {
+fn h256_from_json() {
 	let j = Json::from_str("{ \"with\": \"0x1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef\", \"without\": \"0x1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef\" }").unwrap();
 
 	let v: H256 = xjson!(&j["with"]);
@@ -95,9 +105,33 @@ fn vec_u256_from_json() {
 }
 
 #[test]
-fn vec_h256_from_json_() {
+fn vec_h256_from_json() {
 	let j = Json::from_str("{ \"array\": [ \"1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef\", \"0x1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef\"] }").unwrap();
 
 	let v: Vec<H256> = xjson!(&j["array"]);
 	assert_eq!(vec![H256::from_str("1234567890abcdef1234567890abcdef1234567890abcdef1234567890abcdef").unwrap(); 2], v);
 }
+
+#[test]
+fn simple_types() {
+	let j = Json::from_str("{ \"null\": null, \"empty\": \"\", \"int\": 42, \"dec\": \"42\", \"hex\": \"0x2a\" }").unwrap();
+	let v: u16 = xjson!(&j["int"]);
+	assert_eq!(42u16, v);
+	let v: u32 = xjson!(&j["dec"]);
+	assert_eq!(42u32, v);
+	let v: u64 = xjson!(&j["hex"]);
+	assert_eq!(42u64, v);
+}
+
+#[test]
+fn option_types() {
+	let j = Json::from_str("{ \"null\": null, \"empty\": \"\", \"int\": 42, \"dec\": \"42\", \"hex\": \"0x2a\" }").unwrap();
+	let v: Option<u16> = xjson!(&j["int"]);
+	assert_eq!(Some(42u16), v);
+	let v: Option<u16> = xjson!(&j["dec"]);
+	assert_eq!(Some(42u16), v);
+	let v: Option<u16> = xjson!(&j["null"]);
+	assert_eq!(None, v);
+	let v: Option<u16> = xjson!(&j["empty"]);
+	assert_eq!(None, v);
+}
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