Allow to specify some max number of values for storages in pallet macro. (#8735)

* implement max_values + storages info

* some formatting + doc

* rename StoragesInfo -> PalletStorageInfo

* merge both StorageInfoTrait and PalletStorageInfo

I think it is more future proof. In the future some storage could make
use of multiple prefix. Like one to store how much value has been
inserted, etc...

* Update frame/support/procedural/src/storage/parse.rs

Co-authored-by: Peter Goodspeed-Niklaus <coriolinus@users.noreply.github.com>

* Update frame/support/procedural/src/storage/storage_struct.rs

Co-authored-by: Peter Goodspeed-Niklaus <coriolinus@users.noreply.github.com>

* Fix max_size using hasher information

hasher now expose `max_len` which allows to computes their maximum len.
For hasher without concatenation, it is the size of the hash part,
for hasher with concatenation, it is the size of the hash part + max
encoded len of the key.

* fix tests

* fix ui tests

Co-authored-by: Peter Goodspeed-Niklaus <coriolinus@users.noreply.github.com>

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

@@ -15,7 +15,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-use crate::pallet::{Def, parse::helper::get_doc_literals};
+use crate::pallet::{Def, expand::merge_where_clauses, parse::helper::get_doc_literals};
 
 /// * Add derive trait on Pallet
 /// * Implement GetPalletVersion on Pallet
@@ -24,6 +24,7 @@ use crate::pallet::{Def, parse::helper::get_doc_literals};
 /// * declare Module type alias for construct_runtime
 /// * replace the first field type of `struct Pallet` with `PhantomData` if it is `_`
 /// * implementation of `PalletInfoAccess` information
+/// * implementation of `StorageInfoTrait` on Pallet
 pub fn expand_pallet_struct(def: &mut Def) -> proc_macro2::TokenStream {
 	let frame_support = &def.frame_support;
 	let frame_system = &def.frame_system;
@@ -33,6 +34,10 @@ pub fn expand_pallet_struct(def: &mut Def) -> proc_macro2::TokenStream {
 	let pallet_ident = &def.pallet_struct.pallet;
 	let config_where_clause = &def.config.where_clause;
 
+	let mut storages_where_clauses = vec![&def.config.where_clause];
+	storages_where_clauses.extend(def.storages.iter().map(|storage| &storage.where_clause));
+	let storages_where_clauses = merge_where_clauses(&storages_where_clauses);
+
 	let pallet_item = {
 		let pallet_module_items = &mut def.item.content.as_mut().expect("Checked by def").1;
 		let item = &mut pallet_module_items[def.pallet_struct.index];
@@ -97,6 +102,41 @@ pub fn expand_pallet_struct(def: &mut Def) -> proc_macro2::TokenStream {
 		)
 	};
 
+	let storage_info = if let Some(storage_info_span) = def.pallet_struct.generate_storage_info {
+		let storage_names = &def.storages.iter().map(|storage| &storage.ident).collect::<Vec<_>>();
+		let storage_cfg_attrs = &def.storages.iter()
+			.map(|storage| &storage.cfg_attrs)
+			.collect::<Vec<_>>();
+
+		quote::quote_spanned!(storage_info_span =>
+			impl<#type_impl_gen> #frame_support::traits::StorageInfoTrait
+				for #pallet_ident<#type_use_gen>
+				#storages_where_clauses
+			{
+				fn storage_info()
+					-> #frame_support::sp_std::vec::Vec<#frame_support::traits::StorageInfo>
+				{
+					let mut res = #frame_support::sp_std::vec![];
+
+					#(
+						#(#storage_cfg_attrs)*
+						{
+							let mut storage_info = <
+								#storage_names<#type_use_gen>
+								as #frame_support::traits::StorageInfoTrait
+							>::storage_info();
+							res.append(&mut storage_info);
+						}
+					)*
+
+					res
+				}
+			}
+		)
+	} else {
+		Default::default()
+	};
+
 	quote::quote_spanned!(def.pallet_struct.attr_span =>
 		#module_error_metadata
 
@@ -157,5 +197,7 @@ pub fn expand_pallet_struct(def: &mut Def) -> proc_macro2::TokenStream {
 						implemented by the runtime")
 			}
 		}
+
+		#storage_info
 	)
 }