Error if mismatching # of args for instantiate/call (use-ink#966)

* Error if mismatching # of args for instantiate/call

* Change error message

crates/transcode/src/lib.rs

@@ -205,6 +205,15 @@ impl ContractMessageTranscoder {
             }
         };
 
+        let args: Vec<_> = args.into_iter().collect();
+        if spec_args.len() != args.len() {
+            anyhow::bail!(
+                "Invalid number of input arguments: expected {}, {} provided",
+                spec_args.len(),
+                args.len()
+            )
+        }
+
         let mut encoded = selector.to_bytes().to_vec();
         for (spec, arg) in spec_args.iter().zip(args) {
             let value = scon::parse_value(arg.as_ref())?;
@@ -503,6 +512,26 @@ mod tests {
         Ok(())
     }
 
+    #[test]
+    fn encode_mismatching_args_length() {
+        let metadata = generate_metadata();
+        let transcoder = ContractMessageTranscoder::new(metadata);
+
+        let result: Result<Vec<u8>> = transcoder.encode("new", Vec::<&str>::new());
+        assert!(result.is_err(), "Should return an error");
+        assert_eq!(
+            result.unwrap_err().to_string(),
+            "Invalid number of input arguments: expected 1, 0 provided"
+        );
+
+        let result: Result<Vec<u8>> = transcoder.encode("new", ["true", "false"]);
+        assert!(result.is_err(), "Should return an error");
+        assert_eq!(
+            result.unwrap_err().to_string(),
+            "Invalid number of input arguments: expected 1, 2 provided"
+        );
+    }
+
     #[test]
     fn encode_account_id_custom_ss58_encoding() -> Result<()> {
         let metadata = generate_metadata();