Metadata V16: Implement support for Pallet View Functions (#1981)

* Support Pallet View Functions in Subxt

* fmt

* clippy

* Move a little view function logic to subxt_core

* clippy

* Add back check that prob isnt needed

* avoid vec macro in core

* Add view funciton test and apply various fixes to get it working

* Add test for dynamic view fn call and fix issues

* clippy

* fix test-runtime

* fmt

* remove export

* avoid vec for nostd core

* use const instead of fn for view fn call name

* Update to support latest unstable metadata

* Update metadata stripping tests for new v16 version

codegen/src/api/mod.rs

@@ -9,6 +9,7 @@ mod constants;
 mod custom_values;
 mod errors;
 mod events;
+mod pallet_view_functions;
 mod runtime_apis;
 mod storage;
 
@@ -170,12 +171,19 @@ impl RuntimeGenerator {
 
                 let errors = errors::generate_error_type_alias(&type_gen, pallet)?;
 
+                let view_functions = pallet_view_functions::generate_pallet_view_functions(
+                    &type_gen,
+                    pallet,
+                    &crate_path,
+                )?;
+
                 Ok(quote! {
                     pub mod #mod_name {
                         use super::root_mod;
                         use super::#types_mod_ident;
                         #errors
                         #calls
+                        #view_functions
                         #event
                         #storage_mod
                         #constants_mod
@@ -206,6 +214,12 @@ impl RuntimeGenerator {
             .filter_map(|(pallet, pallet_mod_name)| pallet.call_ty_id().map(|_| pallet_mod_name))
             .collect();
 
+        let pallets_with_view_functions: Vec<_> = pallets_with_mod_names
+            .iter()
+            .filter(|(pallet, _pallet_mod_name)| pallet.has_view_functions())
+            .map(|(_, pallet_mod_name)| pallet_mod_name)
+            .collect();
+
         let rust_items = item_mod_ir.rust_items();
 
         let apis_mod = runtime_apis::generate_runtime_apis(
@@ -283,6 +297,10 @@ impl RuntimeGenerator {
 
                 #apis_mod
 
+                pub fn view_functions() -> ViewFunctionsApi {
+                    ViewFunctionsApi
+                }
+
                 pub fn custom() -> CustomValuesApi {
                     CustomValuesApi
                 }
@@ -316,6 +334,15 @@ impl RuntimeGenerator {
                     )*
                 }
 
+                pub struct ViewFunctionsApi;
+                impl ViewFunctionsApi {
+                    #(
+                        pub fn #pallets_with_view_functions(&self) -> #pallets_with_view_functions::view_functions::ViewFunctionsApi {
+                            #pallets_with_view_functions::view_functions::ViewFunctionsApi
+                        }
+                    )*
+                }
+
                 /// check whether the metadata provided is aligned with this statically generated code.
                 pub fn is_codegen_valid_for(metadata: &#crate_path::Metadata) -> bool {
                     let runtime_metadata_hash = metadata