add constants api to codegen (#402)

* add constants api to codegen Signed-off-by: Gregory Hill <gregorydhill@outlook.com> * handle constant decoding error Signed-off-by: Gregory Hill <gregorydhill@outlook.com> * fix clippy and remove extra constants allocation Signed-off-by: Gregory Hill <gregorydhill@outlook.com>
2026-04-22 09:08:06 +00:00 · 2022-01-27 14:27:20 +00:00
parent 3dded0c600
commit 5f5a7ef5f7
3 changed files with 97 additions and 0 deletions
@@ -0,0 +1,56 @@
+// Copyright 2019-2022 Parity Technologies (UK) Ltd.
+// This file is part of subxt.
+//
+// subxt is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// subxt is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with subxt.  If not, see <http://www.gnu.org/licenses/>.
+
+use crate::types::TypeGenerator;
+use frame_metadata::PalletConstantMetadata;
+use heck::SnakeCase as _;
+use proc_macro2::TokenStream as TokenStream2;
+use quote::{
+    format_ident,
+    quote,
+};
+use scale_info::form::PortableForm;
+
+pub fn generate_constants(
+    type_gen: &TypeGenerator,
+    constants: &[PalletConstantMetadata<PortableForm>],
+    types_mod_ident: &syn::Ident,
+) -> TokenStream2 {
+    let constant_fns = constants.iter().map(|constant| {
+        let fn_name = format_ident!("{}", constant.name.to_snake_case());
+        let return_ty = type_gen.resolve_type_path(constant.ty.id(), &[]);
+
+        let ref_slice = constant.value.as_slice();
+
+        quote! {
+            pub fn #fn_name(&self) -> ::core::result::Result<#return_ty, ::subxt::BasicError> {
+                Ok(::subxt::codec::Decode::decode(&mut &[#(#ref_slice,)*][..])?)
+            }
+        }
+    });
+
+    quote! {
+        pub mod constants {
+            use super::#types_mod_ident;
+
+            pub struct ConstantsApi;
+
+            impl ConstantsApi {
+                #(#constant_fns)*
+            }
+        }
+    }
+}