fix(verify): make verification result an option to handle blockscout's format

ethers-etherscan/src/contract.rs

@@ -331,17 +331,31 @@ impl Client {
         }
 
         let query = self.create_query("contract", "getabi", HashMap::from([("address", address)]));
-        let resp: Response<String> = self.get_json(&query).await?;
-        if resp.result.starts_with("Max rate limit reached") {
+        let resp: Response<Option<String>> = self.get_json(&query).await?;
+
+        let result = match resp.result {
+            Some(result) => result,
+            None => {
+                return Err(EtherscanError::EmptyResult {
+                    message: resp.message,
+                    status: resp.status,
+                })
+            }
+        };
+
+        if result.starts_with("Max rate limit reached") {
             return Err(EtherscanError::RateLimitExceeded)
         }
-        if resp.result.starts_with("Contract source code not verified") {
+
+        if result.starts_with("Contract source code not verified") ||
+            resp.message.starts_with("Contract source code not verified")
+        {
             if let Some(ref cache) = self.cache {
                 cache.set_abi(address, None);
             }
             return Err(EtherscanError::ContractCodeNotVerified(address))
         }
-        let abi = serde_json::from_str(&resp.result)?;
+        let abi = serde_json::from_str(&result)?;
 
         if let Some(ref cache) = self.cache {
             cache.set_abi(address, Some(&abi));

ethers-etherscan/src/errors.rs

@@ -23,6 +23,8 @@ pub enum EtherscanError {
     Serde(#[from] serde_json::Error),
     #[error("Contract source code not verified: {0}")]
     ContractCodeNotVerified(Address),
+    #[error("Response result is unexpectedly empty")]
+    EmptyResult { status: String, message: String },
     #[error("Rate limit exceeded")]
     RateLimitExceeded,
     #[error(transparent)]