Static Metadata Validation (#478)

* metadata: Implement MetadataHashable for deterministic hashing

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

* metadata: Hash `scale_info::Field`

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

* metadata: Hash `scale_info::Variant`

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

* metadata: Hash `scale_info::TypeDef`

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

* metadata: Hash pallet metadata

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

* metadata: Avoid data representation collision via unique identifiers

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

* metadata: Finalize hashing on recursive types

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

* metadata: Cache recursive calls

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

* metadata: Move `MetadataHashable` to codegen to avoid cyclic dependency

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

* codegen: Add pallet unique hash

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

* metadata: Wrap metadata as owned

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

* subxt: Use MetadataHashable wrapper for clients

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

* subxt: Generate runtime pallet uid from metadata

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

* Validate metadata compatibility at the pallet level

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

* Update polkadot.rs

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

* Modify examples and tests for the new API

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

* codegen: Implement metadata uid

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

* Update polkadot with TryFrom implementation

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

* client: Change `to_runtime_api` to reflect TryFrom changes

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

* client: Skip full metadata validation option

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

* codegen: Add option to skip pallet validation for TransactionApi

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

* codegen: Add option to skip pallet validation for StorageApi

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

* Update polkadot.rs with ability to skip pallet validation

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

* codegen: Change `MetadataHashable` to per function implementation

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

* codegen: Use metadata hashes functions

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

* subxt: Use metadata hashes functions

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

* codegen: Make `get_type_uid` private

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

* codegen, subxt: Rename metadata functions `*_uid` to `*_hash`

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

* codegen: Update `get_field_hash` to use `codec::Encode`

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

* subxt: Update polkadot.rs

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

* codegen, subxt: Move metadata check from client to subxt::Metadata

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

* codegen, subxt: Rename metadata check functions to follow `*_hash` naming

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

* codegen: Update polkadot.rs to reflect naming changes

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

* codegen: Use `encode_to` for metadata generation

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

* codegen: Update polkadot.rs to reflect `encode_to` changes

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

* codegen: Specific name for visited set

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

* metadata: Provide cache to hashing functions

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

* metadata: Compute metadata hash by sorted pallets

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

* metadata: Get extrinsic hash

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

* metadata: Extend metadata hash with extrinsic and metadata type

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

* metadata: Add cache as metadata parameter

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

* codegen, subxt: Update metadata hash to use cache

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

* metadata: Implement Default trait for MetadataHasherCache

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

* metadata: Add cache for pallets

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

* metadata: Move functionality to metadata crate

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

* codegen, subxt: Use subxt-metadata crate

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

* codegen: Remove metdata hashing functionality

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

* metadata: Add documentation

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

* metadata: Fix vector capacity to include extrinisc and type hash

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

* metadata: Add empty CLI

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

* metadata-cli: Fetch metadata from substrate nodes

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

* metadata-cli: Log metadata hashes of provided nodes

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

* metadata-cli: Group compatible nodes by metadata

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

* metadata-cli: Simplify hash map insertion

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

* metadata-cli: Move full metadata check to function

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

* metadata-cli: Group metadata validation at the pallet level

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

* subxt: Persist metadata cache

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

* metadata: Move compatibility cli from subxt-metadata to subxt-cli

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

* metadata: Remove cli from subxt-metadata

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

* cli: Fix clippy

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

* metadata: Fix compatible metadata when pallets are registered in different order

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

* tests: Handle result of pallet hashing

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

* metadata: Remove type cache for deterministic hashing

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

* metadata: Add test assets from `substrate-node-template` tag `polkadot-v0.9.17`

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

* metadata-tests: Check cache hashing for Balances pallet

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

* metadata: Fix `get_type_hash` clippy issue

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

* metadata-tests: Compare one time cache with persistent cache

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

* metadata-test: Check metadata hash populates cache for pallets

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

* metadata-tests: Simplify `cache_deterministic_hash` test

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

* metadata-tests: Check deterministic metadata for different order pallets

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

* metadata: Fix clippy

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

* codegen: Implement TransactionApiUnchecked for skipping pallet validation

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

* codegen: Implement StorageApiUnchecked for skipping pallet validation

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

* codegen: Remove skip_pallet_validation boolean

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

* subxt: Implement ClientUnchecked for skipping metadata validation

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

* Update polkadot.rs

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

* Update examples of rpc_call to skip metadata

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

* subxt: Remove heck dependency

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

* codegen: Add pallet name as an identifier for pallet hashing

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

* metadata: Implement MetadataHashDetails

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

* metadata: Adjust testing to `MetadataHashDetails` interface

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

* codegen: Remove extra `pallet_name`

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

* subxt: Update polkadot.rs

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

* subxt: Fix clippy issue

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

* codegen: Change StorageApi to support `_unchecked` methods

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

* codegen: Change TransactionApi to support `_unchecked` methods

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

* subxt: Switch back from `TryFrom` to `From` for `subxt::Client`

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

* codegen, subxt: Remove `ClientUnchecked`

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

* codegen: Expose `validate_metadata` as validation of compatibility method

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

* examples: Update to the new interface

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

* subxt: Update test integration to latest interface

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

* subxt: Update polkadot.rs

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

* metadata/tests: Check different pallet index order

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

* metadata/tests: Check recursive type hashing

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

* metadata/tests: Check recursive types registered in different order

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

* metadata/tests: Fix recursive types warning

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

* metadata/tests: Remove test assets

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

* metadata/tests: Extend tests to verify cached pallet values

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

* examples: Add metadata compatiblity example

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

* examples: Revert balance_transfer to initial form

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

* codegen: Add ConstantsApi metadata check

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

* tests: Modify tests to accomodate ConstantsApi changes

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

* examples: Modify verified version

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

* subxt: Generate polkadot.rs from `0.9.18-4542a603cc-aarch64-macos`

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

* examples: Update polkadot_metadata.scale from `0.9.18-4542a603cc-aarch64-macos`

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

* metadata: Update documentation

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

* tests: Modify default pallet usage

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

* metadata/tests: Remove hex dependency

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

* metadata/tests: Add MetadataTestType to capture complex types

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

* metadata/tests: Update tests to use complex types

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

* metadata/tests: Check metadata correctness via extending pallets

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

* metadata/tests: Extend pallet hash with Events

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

* metadata/tests: Extend pallet hash with constants

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

* metadata/tests: Extend pallet hash with error

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

* examples: Extend metadata compatibiliy with StorageApi and ConstantsApi

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

* Modify comments and documentation

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

* metadata: Benchmarks for full validation and pallet validation

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

* metadata/benches: Fix clippy

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

* metadata: Hash metadata just by inspecting the provided pallets

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

* metadata: Make pallets generic over T for `AsRef<str>`

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

* codegen: Expose the name of the pallets composing the metadata

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

* subxt/tests: Update polkadot.rs with pallets name

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

* codegen: Obtain metadata hash only by inspecting pallets

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

* codegen,subxt: Extend the metadata hash to utilize just pallets

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

* subxt/tests: Update polkadot.rs with client metadata has per pallet

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

* metadata/tests: Test `get_metadata_per_pallet_hash` correctness

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

* metadata: Fix clippy

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

* metadata/benches: Fix decode of metadata

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

* metadata: Fix clippy

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

* [static metadata] validate storage, calls and constants per call (#507)

* validate storage, calls and constants per call

* fix typo

* cache per-thing hashing, move an Arc, remove some unused bits

* create hash_cache to simplify metadata call/constant/storage caching

* simplify/robustify the caching logic to help prevent mismatch between get and set

* cargo fmt

* Fix clippy

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

* bench the per-call metadata functions

* metadata: Add test for `node_template_runtime_variant`

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

* ensure criteron cli opts work

* group benchmarks and avoid unwrap issues

* metadata: Check template runtime for handling the pallet swap order case

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

* metadata: Remove debug logs

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

* metadata: Optimise by removing field's name and type_name and type's path

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

* metadata: Refactor `get_type_hash` to break recursion earlier

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

* subxt: Add tests for `hash_cache`

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

* subxt: Add tests for checking Metadata Inner cache

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

* metadata: Check semantic changes inside enum and struct fields

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

* metadata: Add enums named differently with compatible semantic meaning

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

* metadata: Guard testing of release versions for `node_template_runtime`

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

* Improve documentation

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

* Update polkadot.rs

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

* metadata/tests: Manually construct type of `node_template_runtimeL::Call`

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

* no more special Call handling, avoid a little cloning, and actually sort by name

* remove unused deps and fmt

* RuntimeMetadataLastVersion => RuntimeMetadataV14

* remove a bunch of allocations in the metadata hashing, speed up from ~17ms to ~5ms

* update release docs to release metadata crate too

* subxt: Remove codegen dependency

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

* subxt: Replace std RwLock with parking_lot

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

* subxt/tests: Add ws address to `TestNodeProcess`

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

* subxt/tests: Add metadata validation integration test

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

* subxt: Allow setting metadata on the ClientBuilder

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

* subxt/tests: Check incompatible metadatas

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

* metadata: Fix constant hashing for deterministic output

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

* subxt/tests: Check metadata validation for constants

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

* subxt/tests: Test validation for calls

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

* subxt/tests: Test validation for storage

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

* subxt: Expose `set_metadata` for testing only

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

* subxt: Guard metadata tests under integration-tests

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

Co-authored-by: James Wilson <james@jsdw.me>

codegen/src/api/mod.rs

@@ -37,6 +37,8 @@ mod errors;
 mod events;
 mod storage;
 
+use subxt_metadata::get_metadata_per_pallet_hash;
+
 use super::GeneratedTypeDerives;
 use crate::{
     ir,
@@ -181,9 +183,28 @@ impl RuntimeGenerator {
             })
             .collect::<Vec<_>>();
 
+        // Pallet names and their length are used to create PALLETS array.
+        // The array is used to identify the pallets composing the metadata for
+        // validation of just those pallets.
+        let pallet_names: Vec<_> = self
+            .metadata
+            .pallets
+            .iter()
+            .map(|pallet| &pallet.name)
+            .collect();
+        let pallet_names_len = pallet_names.len();
+
+        let metadata_hash = get_metadata_per_pallet_hash(&self.metadata, &pallet_names);
+
         let modules = pallets_with_mod_names.iter().map(|(pallet, mod_name)| {
             let calls = if let Some(ref calls) = pallet.calls {
-                calls::generate_calls(&type_gen, pallet, calls, types_mod_ident)
+                calls::generate_calls(
+                    &self.metadata,
+                    &type_gen,
+                    pallet,
+                    calls,
+                    types_mod_ident,
+                )
             } else {
                 quote!()
             };
@@ -195,13 +216,20 @@ impl RuntimeGenerator {
             };
 
             let storage_mod = if let Some(ref storage) = pallet.storage {
-                storage::generate_storage(&type_gen, pallet, storage, types_mod_ident)
+                storage::generate_storage(
+                    &self.metadata,
+                    &type_gen,
+                    pallet,
+                    storage,
+                    types_mod_ident,
+                )
             } else {
                 quote!()
             };
 
             let constants_mod = if !pallet.constants.is_empty() {
                 constants::generate_constants(
+                    &self.metadata,
                     &type_gen,
                     pallet,
                     &pallet.constants,
@@ -244,24 +272,26 @@ impl RuntimeGenerator {
         };
 
         let mod_ident = item_mod_ir.ident;
-        let pallets_with_constants =
-            pallets_with_mod_names
-                .iter()
-                .filter_map(|(pallet, pallet_mod_name)| {
-                    (!pallet.constants.is_empty()).then(|| pallet_mod_name)
-                });
-        let pallets_with_storage =
-            pallets_with_mod_names
-                .iter()
-                .filter_map(|(pallet, pallet_mod_name)| {
-                    pallet.storage.as_ref().map(|_| pallet_mod_name)
-                });
-        let pallets_with_calls =
-            pallets_with_mod_names
-                .iter()
-                .filter_map(|(pallet, pallet_mod_name)| {
-                    pallet.calls.as_ref().map(|_| pallet_mod_name)
-                });
+        let pallets_with_constants: Vec<_> = pallets_with_mod_names
+            .iter()
+            .filter_map(|(pallet, pallet_mod_name)| {
+                (!pallet.constants.is_empty()).then(|| pallet_mod_name)
+            })
+            .collect();
+
+        let pallets_with_storage: Vec<_> = pallets_with_mod_names
+            .iter()
+            .filter_map(|(pallet, pallet_mod_name)| {
+                pallet.storage.as_ref().map(|_| pallet_mod_name)
+            })
+            .collect();
+
+        let pallets_with_calls: Vec<_> = pallets_with_mod_names
+            .iter()
+            .filter_map(|(pallet, pallet_mod_name)| {
+                pallet.calls.as_ref().map(|_| pallet_mod_name)
+            })
+            .collect();
 
         let has_module_error_impl =
             errors::generate_has_module_error_impl(&self.metadata, types_mod_ident);
@@ -271,6 +301,8 @@ impl RuntimeGenerator {
             pub mod #mod_ident {
                 // Make it easy to access the root via `root_mod` at different levels:
                 use super::#mod_ident as root_mod;
+                // Identify the pallets composing the static metadata by name.
+                pub static PALLETS: [&str; #pallet_names_len] = [ #(#pallet_names,)* ];
 
                 #outer_event
                 #( #modules )*
@@ -301,6 +333,14 @@ impl RuntimeGenerator {
                     T: ::subxt::Config,
                     X: ::subxt::extrinsic::ExtrinsicParams<T>,
                 {
+                    pub fn validate_metadata(&'a self) -> Result<(), ::subxt::MetadataError> {
+                        if self.client.metadata().metadata_hash(&PALLETS) != [ #(#metadata_hash,)* ] {
+                            Err(::subxt::MetadataError::IncompatibleMetadata)
+                        } else {
+                            Ok(())
+                        }
+                    }
+
                     pub fn constants(&'a self) -> ConstantsApi<'a, T> {
                         ConstantsApi { client: &self.client }
                     }
@@ -384,12 +424,13 @@ impl RuntimeGenerator {
     }
 }
 
+/// Return a vector of tuples of variant names and corresponding struct definitions.
 pub fn generate_structs_from_variants<'a, F>(
     type_gen: &'a TypeGenerator,
     type_id: u32,
     variant_to_struct_name: F,
     error_message_type_name: &str,
-) -> Vec<CompositeDef>
+) -> Vec<(String, CompositeDef)>
 where
     F: Fn(&str) -> std::borrow::Cow<str>,
 {
@@ -406,14 +447,15 @@ where
                     &[],
                     type_gen,
                 );
-                CompositeDef::struct_def(
+                let struct_def = CompositeDef::struct_def(
                     struct_name.as_ref(),
                     Default::default(),
                     fields,
                     Some(parse_quote!(pub)),
                     type_gen,
                     var.docs(),
-                )
+                );
+                (var.name().to_string(), struct_def)
             })
             .collect()
     } else {