Use the generated DispatchError instead of the hardcoded Substrate one #394
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,171 @@ | ||
| // 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/>. | ||
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| use frame_metadata::v14::RuntimeMetadataV14; | ||
| use proc_macro2::{ | ||
| Span as Span2, | ||
| TokenStream as TokenStream2, | ||
| }; | ||
| use quote::quote; | ||
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| pub struct ErrorDetails { | ||
| pub type_def: TokenStream2, | ||
| pub dispatch_error_impl_fn: TokenStream2, | ||
| } | ||
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| impl ErrorDetails { | ||
| fn emit_compile_error(err: &str) -> ErrorDetails { | ||
| let err_lit_str = syn::LitStr::new(err, Span2::call_site()); | ||
| ErrorDetails { | ||
| type_def: quote!(), | ||
| dispatch_error_impl_fn: quote!(compile_error!(#err_lit_str)), | ||
| } | ||
| } | ||
| } | ||
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| /// The purpose of this is to enumerate all of the possible `(module_index, error_index)` error | ||
| /// variants, so that we can convert `u8` error codes inside a generated `DispatchError` into | ||
| /// nicer error strings with documentation. To do this, we emit the type we'll return instances of, | ||
| /// and a function that returns such an instance for all of the error codes seen in the metadata. | ||
| pub fn generate_error_details(metadata: &RuntimeMetadataV14) -> ErrorDetails { | ||
| let errors = match pallet_errors(metadata) { | ||
| Ok(errors) => errors, | ||
| Err(e) => { | ||
| let err_string = | ||
| format!("Failed to generate error details from metadata: {}", e); | ||
| return ErrorDetails::emit_compile_error(&err_string) | ||
| } | ||
| }; | ||
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| let match_body_items = errors.into_iter().map(|err| { | ||
| let docs = err.description(); | ||
| let pallet_index = err.pallet_index; | ||
| let error_index = err.error_index; | ||
| let pallet_name = err.pallet; | ||
| let error_name = err.error; | ||
|
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| quote! { | ||
| (#pallet_index, #error_index) => Some(ErrorDetails { | ||
| pallet: #pallet_name, | ||
| error: #error_name, | ||
| docs: #docs | ||
| }) | ||
| } | ||
| }); | ||
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| ErrorDetails { | ||
| // A type we'll be returning that needs defining at the top level: | ||
| type_def: quote! { | ||
| pub struct ErrorDetails { | ||
| pub pallet: &'static str, | ||
| pub error: &'static str, | ||
| pub docs: &'static str, | ||
| } | ||
| }, | ||
| // A function which will live in an impl block for our DispatchError, | ||
| // to statically return details for known error types: | ||
| dispatch_error_impl_fn: quote! { | ||
| pub fn details(&self) -> Option<ErrorDetails> { | ||
| if let Self::Module { index, error } = self { | ||
| match (index, error) { | ||
| #( #match_body_items ),*, | ||
| _ => None | ||
| } | ||
| } else { | ||
| None | ||
| } | ||
| } | ||
| }, | ||
| } | ||
| } | ||
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| fn pallet_errors( | ||
| metadata: &RuntimeMetadataV14, | ||
| ) -> Result<Vec<ErrorMetadata>, InvalidMetadataError> { | ||
| let get_type_def_variant = |type_id: u32| { | ||
| let ty = metadata | ||
| .types | ||
| .resolve(type_id) | ||
| .ok_or(InvalidMetadataError::MissingType(type_id))?; | ||
| if let scale_info::TypeDef::Variant(var) = ty.type_def() { | ||
| Ok(var) | ||
| } else { | ||
| Err(InvalidMetadataError::TypeDefNotVariant(type_id)) | ||
| } | ||
| }; | ||
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| let pallet_errors = metadata | ||
| .pallets | ||
| .iter() | ||
| .filter_map(|pallet| { | ||
| pallet.error.as_ref().map(|error| { | ||
| let type_def_variant = get_type_def_variant(error.ty.id())?; | ||
| Ok((pallet, type_def_variant)) | ||
| }) | ||
| }) | ||
| .collect::<Result<Vec<(_, _)>, _>>()?; | ||
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| let errors = pallet_errors | ||
| .iter() | ||
| .flat_map(|(pallet, type_def_variant)| { | ||
| type_def_variant.variants().iter().map(move |var| { | ||
| ErrorMetadata { | ||
| pallet_index: pallet.index, | ||
| error_index: var.index(), | ||
| pallet: pallet.name.clone(), | ||
| error: var.name().clone(), | ||
| variant: var.clone(), | ||
| } | ||
| }) | ||
| }) | ||
| .collect(); | ||
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| Ok(errors) | ||
| } | ||
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| #[derive(Clone, Debug)] | ||
| pub struct ErrorMetadata { | ||
|
There was a problem hiding this comment. Missing docs here. Also, what do you think about moving this to the top? |
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| pub pallet_index: u8, | ||
| pub error_index: u8, | ||
| pub pallet: String, | ||
| pub error: String, | ||
| variant: scale_info::Variant<scale_info::form::PortableForm>, | ||
|
There was a problem hiding this comment. dq: what is the reason for storing the variant for? There was a problem hiding this comment. Yup, that's it! I'm not sure why I did/left this now. I've made it be just the doc string, which simplifies things a bit! |
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| } | ||
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| impl ErrorMetadata { | ||
| pub fn description(&self) -> String { | ||
| self.variant.docs().join("\n") | ||
|
There was a problem hiding this comment. So if the node is compiled to strip the docs, this will be empty? Worth detecting and add some kind of default, "No docs available in the metadata"? There was a problem hiding this comment. In the empty case docs will just be "", which seems good enough (that can be detected and handled down the line in whichever way things prefer) |
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| } | ||
| } | ||
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| #[derive(Debug)] | ||
| pub enum InvalidMetadataError { | ||
|
There was a problem hiding this comment. Ah; doesn't need to be |
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| MissingType(u32), | ||
| TypeDefNotVariant(u32), | ||
| } | ||
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| impl std::fmt::Display for InvalidMetadataError { | ||
| fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result { | ||
| match self { | ||
| InvalidMetadataError::MissingType(n) => { | ||
| write!(f, "Type {} missing from type registry", n) | ||
| } | ||
| InvalidMetadataError::TypeDefNotVariant(n) => { | ||
| write!(f, "Type {} was not a variant/enum type", n) | ||
| } | ||
| } | ||
| } | ||
| } | ||
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Maybe we can unify these two chains into a single? Like, why collect the
pallet_errorsfirst and then build theerrorsVec?There was a problem hiding this comment.
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It might be a bit tricky; we end up with
Result<_>Items just prior to that collect, so the collecting I think is just there to give a chance to bail if we encounter any errors! I'll see whether I can do it in a clean way!There was a problem hiding this comment.
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I settled on standard for loops; it felt tidier: