feat: impl Deserialize for block number (#497)

ethers-core/src/types/block.rs

@@ -1,6 +1,7 @@
 // Taken from https://github.com/tomusdrw/rust-web3/blob/master/src/types/block.rs
 use crate::types::{Address, Bloom, Bytes, H256, U256, U64};
-use serde::{ser::SerializeStruct, Deserialize, Serialize, Serializer};
+use serde::{ser::SerializeStruct, Deserialize, Deserializer, Serialize, Serializer};
+use std::str::FromStr;
 
 /// The block type returned from RPC calls.
 /// This is generic over a `TX` type which will be either the hash or the
@@ -192,12 +193,46 @@ impl Serialize for BlockNumber {
     }
 }
 
+impl<'de> Deserialize<'de> for BlockNumber {
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where
+        D: Deserializer<'de>,
+    {
+        let s = String::deserialize(deserializer)?.to_lowercase();
+        Ok(match s.as_str() {
+            "latest" => Self::Latest,
+            "earliest" => Self::Earliest,
+            "pending" => Self::Pending,
+            n => BlockNumber::Number(U64::from_str(n).map_err(serde::de::Error::custom)?),
+        })
+    }
+}
+
 #[cfg(test)]
 #[cfg(not(feature = "celo"))]
 mod tests {
     use super::*;
     use crate::types::{Transaction, TxHash};
 
+    #[test]
+    fn serde_block_number() {
+        for b in vec![
+            BlockNumber::Latest,
+            BlockNumber::Earliest,
+            BlockNumber::Pending,
+        ] {
+            let b_ser = serde_json::to_string(&b).unwrap();
+            let b_de: BlockNumber = serde_json::from_str(&b_ser).unwrap();
+            assert_eq!(b_de, b);
+        }
+
+        let b = BlockNumber::Number(1042u64.into());
+        let b_ser = serde_json::to_string(&b).unwrap();
+        let b_de: BlockNumber = serde_json::from_str(&b_ser).unwrap();
+        assert_eq!(b_ser, "\"0x412\"");
+        assert_eq!(b_de, b);
+    }
+
     #[test]
     fn deserialize_blk_no_txs() {
         let block = r#"{"number":"0x3","hash":"0xda53da08ef6a3cbde84c33e51c04f68c3853b6a3731f10baa2324968eee63972","parentHash":"0x689c70c080ca22bc0e681694fa803c1aba16a69c8b6368fed5311d279eb9de90","mixHash":"0x0000000000000000000000000000000000000000000000000000000000000000","nonce":"0x0000000000000000","sha3Uncles":"0x1dcc4de8dec75d7aab85b567b6ccd41ad312451b948a7413f0a142fd40d49347","logsBloom":"0x00000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000","transactionsRoot":"0x7270c1c4440180f2bd5215809ee3d545df042b67329499e1ab97eb759d31610d","stateRoot":"0x29f32984517a7d25607da485b23cefabfd443751422ca7e603395e1de9bc8a4b","receiptsRoot":"0x056b23fbba480696b65fe5a59b8f2148a1299103c4f57df839233af2cf4ca2d2","miner":"0x0000000000000000000000000000000000000000","difficulty":"0x0","totalDifficulty":"0x0","extraData":"0x","size":"0x3e8","gasLimit":"0x6691b7","gasUsed":"0x5208","timestamp":"0x5ecedbb9","transactions":["0xc3c5f700243de37ae986082fd2af88d2a7c2752a0c0f7b9d6ac47c729d45e067"],"uncles":[]}"#;