Handle sp_runtime::ModuleError substrate updates (#492)

* codegen: Handle new errors of type [u8; 4] with backwards compatibility

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* codegen: Add comments about the compatibility of `DispatchError::Module`

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* codegen: Handle legacy cases appropriately

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* codegen: Introduce `ModuleErrorType` for compatibility versioning

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* codegen: Implement `module_error_type` helper

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* codegen: Implement `quote::ToTokens` for `ModuleErrorType`

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* codegen: Rename new error to ArrayError

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* codegen: Add strict checks for ModuleError

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* codegen: Fix cargo fmt

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* codegen, subxt: Expose the error's raw bytes to user

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* subxt: Update polkadot with ModuleErrorRaw

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* subxt: Rename `ModuleErrorRaw` to `ModuleErrorData`

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* subxt: Expose method to obtain error index

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

* codegen: Rename `ModuleErrorRaw` to `ModuleErrorData`

Signed-off-by: Alexandru Vasile <alexandru.vasile@parity.io>

subxt/src/error.rs

@@ -182,6 +182,28 @@ pub struct ModuleError {
     pub error: String,
     /// A description of the error.
     pub description: Vec<String>,
+    /// A byte representation of the error.
+    pub error_data: ModuleErrorData,
+}
+
+/// The error details about a module error that has occurred.
+///
+/// **Note**: Structure used to obtain the underlying bytes of a ModuleError.
+#[derive(Clone, Debug, thiserror::Error)]
+#[error("Pallet index {pallet_index}: raw error: {error:?}")]
+pub struct ModuleErrorData {
+    /// Index of the pallet that the error came from.
+    pub pallet_index: u8,
+    /// Raw error bytes.
+    pub error: [u8; 4],
+}
+
+impl ModuleErrorData {
+    /// Obtain the error index from the underlying byte data.
+    pub fn error_index(&self) -> u8 {
+        // Error index is utilized as the first byte from the error array.
+        self.error[0]
+    }
 }
 
 /// This trait is automatically implemented for the generated `DispatchError`,
@@ -190,5 +212,5 @@ pub struct ModuleError {
 pub trait HasModuleError {
     /// If the error has a `Module` variant, return a tuple of the
     /// pallet index and error index. Else, return `None`.
-    fn module_error_indices(&self) -> Option<(u8, u8)>;
+    fn module_error_data(&self) -> Option<ModuleErrorData>;
 }

subxt/src/lib.rs

@@ -81,6 +81,7 @@ pub use crate::{
         Error,
         GenericError,
         HasModuleError,
+        ModuleErrorData,
         RuntimeError,
         TransactionError,
     },

subxt/src/transaction.rs

@@ -389,14 +389,17 @@ impl<'client, T: Config, E: Decode + HasModuleError, Evs: Decode>
             let ev = ev?;
             if &ev.pallet == "System" && &ev.variant == "ExtrinsicFailed" {
                 let dispatch_error = E::decode(&mut &*ev.data)?;
-                if let Some((pallet_idx, error_idx)) =
-                    dispatch_error.module_error_indices()
-                {
-                    let details = self.client.metadata().error(pallet_idx, error_idx)?;
+                if let Some(error_data) = dispatch_error.module_error_data() {
+                    // Error index is utilized as the first byte from the error array.
+                    let details = self
+                        .client
+                        .metadata()
+                        .error(error_data.pallet_index, error_data.error_index())?;
                     return Err(Error::Module(ModuleError {
                         pallet: details.pallet().to_string(),
                         error: details.error().to_string(),
                         description: details.description().to_vec(),
+                        error_data,
                     }))
                 } else {
                     return Err(Error::Runtime(RuntimeError(dispatch_error)))