Add std::error::Error impls (#217)

* Add std::error::Error impls

* Use source instead of cause.

* Fix warning.

.editorconfig

@@ -1,7 +1,7 @@
 root = true
 [*]
 indent_style=space
-indent_size=2
+indent_size=4
 tab_width=4
 end_of_line=lf
 charset=utf-8

src/contract/error.rs

@@ -3,10 +3,10 @@
 use ethabi::Error as EthError;
 
 use crate::error::Error as ApiError;
-use derive_more::Display;
+use derive_more::{Display, From};
 
 /// Contract error.
-#[derive(Debug, Display)]
+#[derive(Debug, Display, From)]
 pub enum Error {
     /// invalid output type requested by the caller
     #[display(fmt = "Invalid output type: {}", _0)]
@@ -19,25 +19,23 @@ pub enum Error {
     Api(ApiError),
 }
 
-impl From<EthError> for Error {
-    fn from(e: EthError) -> Self {
-        Error::Abi(e)
-    }
-}
-
-impl From<ApiError> for Error {
-    fn from(e: ApiError) -> Self {
-        Error::Api(e)
+impl std::error::Error for Error {
+    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
+        match *self {
+            Error::InvalidOutputType(_) => None,
+            Error::Abi(ref e) => Some(e),
+            Error::Api(ref e) => Some(e),
+        }
     }
 }
 
 pub mod deploy {
     use crate::error::Error as ApiError;
     use crate::types::H256;
-    use derive_more::Display;
+    use derive_more::{Display, From};
 
     /// Contract deployment error.
-    #[derive(Debug, Display)]
+    #[derive(Debug, Display, From)]
     pub enum Error {
         /// Rpc error
         #[display(fmt = "Api error: {}", _0)]
@@ -47,9 +45,12 @@ pub mod deploy {
         ContractDeploymentFailure(H256),
     }
 
-    impl From<ApiError> for Error {
-        fn from(e: ApiError) -> Self {
-            Error::Api(e)
+    impl std::error::Error for Error {
+        fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
+            match *self {
+                Error::Api(ref e) => Some(e),
+                Error::ContractDeploymentFailure(_) => None,
+            }
         }
     }
 }

src/error.rs

@@ -1,11 +1,11 @@
 //! Web3 Error
 use crate::rpc::error::Error as RPCError;
-use derive_more::Display;
+use derive_more::{Display, From};
 use serde_json::Error as SerdeError;
 use std::io::Error as IoError;
 
 /// Errors which can occur when attempting to generate resource uri.
-#[derive(Debug, Display)]
+#[derive(Debug, Display, From)]
 pub enum Error {
     /// server is unreachable
     #[display(fmt = "Server is unreachable")]
@@ -30,15 +30,14 @@ pub enum Error {
     Internal,
 }
 
-impl From<IoError> for Error {
-    fn from(e: IoError) -> Self {
-        Error::Io(e)
-    }
-}
-
-impl From<RPCError> for Error {
-    fn from(e: RPCError) -> Self {
-        Error::Rpc(e)
+impl std::error::Error for Error {
+    fn source(&self) -> Option<&(dyn std::error::Error + 'static)> {
+        use self::Error::*;
+        match *self {
+            Unreachable | Decoder(_) | InvalidResponse(_) | Transport(_) | Internal => None,
+            Rpc(ref e) => Some(e),
+            Io(ref e) => Some(e),
+        }
     }
 }
 

src/types/trace_filtering.rs

@@ -102,7 +102,7 @@ pub struct Trace {
     pub block_hash: H256,
     #[serde(rename = "type")]
     action_type: ActionType,
-    // Error
+    /// Error
     pub error: Option<String>,
 }