[After Transaction Extension PR] CheckMetadataHash transaction extension benchmark.

Cargo.toml

@@ -668,6 +668,7 @@ codec = { version = "3.6.12", default-features = false, package = "parity-scale-
 collectives-westend-emulated-chain = { path = "cumulus/parachains/integration-tests/emulated/chains/parachains/collectives/collectives-westend" }
 collectives-westend-runtime = { path = "cumulus/parachains/runtimes/collectives/collectives-westend" }
 color-eyre = { version = "0.6.1", default-features = false }
+const-hex = { version = "1.10.0", default-features = false }
 color-print = { version = "0.3.4" }
 colored = { version = "2.0.4" }
 comfy-table = { version = "7.1.0", default-features = false }

substrate/frame/metadata-hash-extension/Cargo.toml

@@ -17,6 +17,7 @@ frame-support = { workspace = true }
 frame-system = { workspace = true }
 log = { workspace = true }
 docify = { workspace = true }
+const-hex = { workspace = true }
 
 [dev-dependencies]
 substrate-wasm-builder = { features = ["metadata-hash"], workspace = true, default-features = true }
@@ -36,4 +37,5 @@ std = [
 	"log/std",
 	"scale-info/std",
 	"sp-runtime/std",
+	"const-hex/std",
 ]

substrate/frame/metadata-hash-extension/src/lib.rs

@@ -39,7 +39,7 @@ extern crate alloc;
 extern crate self as frame_metadata_hash_extension;
 
 use codec::{Decode, Encode};
-use frame_support::DebugNoBound;
+use frame_support::{pallet_prelude::Weight, DebugNoBound};
 use frame_system::Config;
 use scale_info::TypeInfo;
 use sp_runtime::{
@@ -68,12 +68,20 @@ enum MetadataHash {
 	Custom([u8; 32]),
 }
 
+const RUNTIME_METADATA: Option<[u8; 32]> = if let Some(hex) = option_env!("RUNTIME_METADATA_HASH") {
+	match const_hex::const_decode_to_array(hex.as_bytes()) {
+		Ok(hex) => Some(hex),
+		Err(_) => None,
+	}
+} else {
+	None
+};
+
 impl MetadataHash {
 	/// Returns the metadata hash.
 	fn hash(&self) -> Option<[u8; 32]> {
 		match self {
-			Self::FetchFromEnv =>
-				option_env!("RUNTIME_METADATA_HASH").map(array_bytes::hex2array_unchecked),
+			Self::FetchFromEnv => RUNTIME_METADATA,
 			Self::Custom(hash) => Some(*hash),
 		}
 	}
@@ -152,6 +160,9 @@ impl<T: Config + Send + Sync> TransactionExtensionBase for CheckMetadataHash<T>
 
 		Ok(signed)
 	}
+	fn weight() -> Weight {
+		Weight::default()
+	}
 }
 impl<T: Config + Send + Sync> TransactionExtension<T::RuntimeCall> for CheckMetadataHash<T> {
 	type Val = ();