Allow renaming storage item prefixes (#9016)

* Implement parsing for #[pallet::storage_name] on storage items

* Rename storage prefix when a #[pallet::storage_name] is supplied

* Fix test_storage_info

* Rename storage_name to storage_prefix

* Check for duplicates when renaming storage prefixes

* Allow only string literals for storage_prefix renames

* Use proper spans for attribute errors

* Check for valid identifiers when parsing storage prefix renames

substrate/frame/support/procedural/src/pallet/expand/storage.rs

@@ -15,22 +15,48 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use crate::pallet::Def;
+use crate::pallet::{Def, parse::storage::StorageDef};
 use crate::pallet::parse::storage::{Metadata, QueryKind, StorageGenerics};
 use frame_support_procedural_tools::clean_type_string;
+use std::collections::HashSet;
 
 /// Generate the prefix_ident related the the storage.
 /// prefix_ident is used for the prefix struct to be given to storage as first generic param.
-fn prefix_ident(storage_ident: &syn::Ident) -> syn::Ident {
+fn prefix_ident(storage: &StorageDef) -> syn::Ident {
+	let storage_ident = &storage.ident;
 	syn::Ident::new(&format!("_GeneratedPrefixForStorage{}", storage_ident), storage_ident.span())
 }
 
+/// Check for duplicated storage prefixes. This step is necessary since users can specify an
+/// alternative storage prefix using the #[pallet::storage_prefix] syntax, and we need to ensure
+/// that the prefix specified by the user is not a duplicate of an existing one.
+fn check_prefix_duplicates(
+	storage_def: &StorageDef,
+	set: &mut HashSet<String>,
+) -> syn::Result<()> {
+	let prefix = storage_def.prefix();
+
+	if !set.insert(prefix.clone()) {
+		let err = syn::Error::new(
+			storage_def.prefix_span(),
+			format!("Duplicate storage prefixes found for `{}`", prefix),
+		);
+		return Err(err);
+	}
+
+	Ok(())
+}
+
 /// * if generics are unnamed: replace the first generic `_` by the generated prefix structure
 /// * if generics are named: reorder the generic, remove their name, and add the missing ones.
 /// * Add `#[allow(type_alias_bounds)]`
-pub fn process_generics(def: &mut Def) {
+pub fn process_generics(def: &mut Def) -> syn::Result<()> {
 	let frame_support = &def.frame_support;
+	let mut prefix_set = HashSet::new();
+
 	for storage_def in def.storages.iter_mut() {
+		check_prefix_duplicates(storage_def, &mut prefix_set)?;
+
 		let item = &mut def.item.content.as_mut().expect("Checked by def").1[storage_def.index];
 
 		let typ_item = match item {
@@ -50,7 +76,7 @@ pub fn process_generics(def: &mut Def) {
 			_ => unreachable!("Checked by def"),
 		};
 
-		let prefix_ident = prefix_ident(&storage_def.ident);
+		let prefix_ident = prefix_ident(&storage_def);
 		let type_use_gen = if def.config.has_instance {
 			quote::quote_spanned!(storage_def.attr_span => T, I)
 		} else {
@@ -116,6 +142,8 @@ pub fn process_generics(def: &mut Def) {
 			args.args[0] = syn::parse_quote!( #prefix_ident<#type_use_gen> );
 		}
 	}
+
+	Ok(())
 }
 
 /// * generate StoragePrefix structs (e.g. for a storage `MyStorage` a struct with the name
@@ -125,7 +153,9 @@ pub fn process_generics(def: &mut Def) {
 /// * Add `#[allow(type_alias_bounds)]` on storages type alias
 /// * generate metadatas
 pub fn expand_storages(def: &mut Def) -> proc_macro2::TokenStream {
-	process_generics(def);
+	if let Err(e) = process_generics(def) {
+		return e.into_compile_error().into();
+	}
 
 	let frame_support = &def.frame_support;
 	let frame_system = &def.frame_system;
@@ -344,9 +374,9 @@ pub fn expand_storages(def: &mut Def) -> proc_macro2::TokenStream {
 	let prefix_structs = def.storages.iter().map(|storage_def| {
 		let type_impl_gen = &def.type_impl_generics(storage_def.attr_span);
 		let type_use_gen = &def.type_use_generics(storage_def.attr_span);
-		let prefix_struct_ident = prefix_ident(&storage_def.ident);
+		let prefix_struct_ident = prefix_ident(&storage_def);
 		let prefix_struct_vis = &storage_def.vis;
-		let prefix_struct_const = storage_def.ident.to_string();
+		let prefix_struct_const = storage_def.prefix();
 		let config_where_clause = &def.config.where_clause;
 
 		let cfg_attrs = &storage_def.cfg_attrs;