sp-api: Put frame-metadata behind some feature (#14398)

* sp-api: Put `frame-metadata` behind some feature

Closes: https://github.com/paritytech/substrate/issues/14296

* ".git/.scripts/commands/fmt/fmt.sh"

* Review feedback

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Co-authored-by: command-bot <>

substrate/primitives/api/proc-macro/src/decl_runtime_apis.rs

@@ -20,7 +20,6 @@ use crate::{
 		API_VERSION_ATTRIBUTE, BLOCK_GENERIC_IDENT, CHANGED_IN_ATTRIBUTE, CORE_TRAIT_ATTRIBUTE,
 		RENAMED_ATTRIBUTE, SUPPORTED_ATTRIBUTE_NAMES,
 	},
-	runtime_metadata::generate_decl_runtime_metadata,
 	utils::{
 		extract_parameter_names_types_and_borrows, fold_fn_decl_for_client_side,
 		generate_crate_access, generate_runtime_mod_name_for_trait, parse_runtime_api_version,
@@ -188,13 +187,17 @@ fn generate_runtime_decls(decls: &[ItemTrait]) -> Result<TokenStream> {
 		let mut decl = decl.clone();
 		let decl_span = decl.span();
 		extend_generics_with_block(&mut decl.generics);
-		let metadata = generate_decl_runtime_metadata(&decl);
 		let mod_name = generate_runtime_mod_name_for_trait(&decl.ident);
 		let found_attributes = remove_supported_attributes(&mut decl.attrs);
 		let api_version =
 			get_api_version(&found_attributes).map(|v| generate_runtime_api_version(v as u32))?;
 		let id = generate_runtime_api_id(&decl.ident.to_string());
 
+		#[cfg(feature = "frame-metadata")]
+		let metadata = crate::runtime_metadata::generate_decl_runtime_metadata(&decl);
+		#[cfg(not(feature = "frame-metadata"))]
+		let metadata = quote!();
+
 		let trait_api_version = get_api_version(&found_attributes)?;
 
 		let mut methods_by_version: BTreeMap<u64, Vec<TraitItemFn>> = BTreeMap::new();