Custom error decoder (#3783)

automerge

programs/token_api/Cargo.toml

@@ -11,6 +11,8 @@ edition = "2018"
 [dependencies]
 bincode = "1.1.3"
 log = "0.4.2"
+num-derive = "0.2"
+num-traits = "0.2"
 serde = "1.0.90"
 serde_derive = "1.0.90"
 solana-logger = { path = "../../logger", version = "0.14.0" }

programs/token_api/src/token_state.rs

@@ -1,15 +1,23 @@
 use log::*;
+use num_derive::FromPrimitive;
 use serde_derive::{Deserialize, Serialize};
 use solana_sdk::account::KeyedAccount;
+use solana_sdk::instruction_processor_utils::DecodeError;
 use solana_sdk::pubkey::Pubkey;
 
-#[derive(Serialize, Debug, PartialEq)]
+#[derive(Serialize, Debug, PartialEq, FromPrimitive)]
 pub enum TokenError {
     InvalidArgument,
     InsufficentFunds,
     NotOwner,
 }
 
+impl<T> DecodeError<T> for TokenError {
+    fn type_of(&self) -> &'static str {
+        "TokenError"
+    }
+}
+
 impl std::fmt::Display for TokenError {
     fn fmt(&self, f: &mut std::fmt::Formatter) -> std::fmt::Result {
         write!(f, "error")