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runtime-sdk: Implement automatic MigrationHandler derivation
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167 changes: 167 additions & 0 deletions
167
runtime-sdk-macros/src/module_derive/migration_handler.rs
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,167 @@ | ||
| use std::collections::HashSet; | ||
|
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| use proc_macro2::TokenStream; | ||
| use quote::quote; | ||
|
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| use crate::emit_compile_error; | ||
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| /// Deriver for the `MigrationHandler` trait. | ||
| pub struct DeriveMigrationHandler { | ||
| /// Item defining the `MigrationHandler::Genesis` associated type. | ||
| genesis_ty: Option<syn::ImplItem>, | ||
| /// Migration functions. | ||
| migrate_fns: Vec<MigrateFn>, | ||
| } | ||
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| struct MigrateFn { | ||
| item: syn::ImplItem, | ||
| ident: syn::Ident, | ||
| from_version: u32, | ||
| } | ||
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| impl DeriveMigrationHandler { | ||
| pub fn new() -> Box<Self> { | ||
| Box::new(Self { | ||
| genesis_ty: None, | ||
| migrate_fns: vec![], | ||
| }) | ||
| } | ||
| } | ||
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| impl super::Deriver for DeriveMigrationHandler { | ||
| fn preprocess(&mut self, item: syn::ImplItem) -> Option<syn::ImplItem> { | ||
| match item { | ||
| // We are looking for a `type Genesis = ...;` item. | ||
| syn::ImplItem::Type(ref ty) if &ty.ident.to_string() == "Genesis" => { | ||
| self.genesis_ty = Some(item); | ||
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| None // Take the item. | ||
| } | ||
| syn::ImplItem::Fn(ref f) => { | ||
| // Check whether a `migration` attribute is set for the method. | ||
| if let Some(attrs) = parse_attrs(&f.attrs) { | ||
| self.migrate_fns.push(MigrateFn { | ||
| ident: f.sig.ident.clone(), | ||
| from_version: attrs.from_version, | ||
| item, | ||
| }); | ||
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| None | ||
| } else { | ||
| Some(item) // Return the item. | ||
| } | ||
| } | ||
| _ => Some(item), // Return the item. | ||
| } | ||
| } | ||
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| fn derive(&mut self, generics: &syn::Generics, ty: &Box<syn::Type>) -> TokenStream { | ||
| let genesis_ty = if let Some(genesis_ty) = &self.genesis_ty { | ||
| genesis_ty | ||
| } else { | ||
| return quote! {}; | ||
| }; | ||
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| let mut seen_versions = HashSet::new(); | ||
| let (migrate_fns, mut migrate_arms): (Vec<_>, Vec<_>) = self.migrate_fns.iter().map(|f| { | ||
| let MigrateFn { item, ident, from_version } = f; | ||
| if seen_versions.contains(from_version) { | ||
| emit_compile_error(format!( | ||
| "Duplicate migration for version: {from_version}" | ||
| )); | ||
| } | ||
| seen_versions.insert(from_version); | ||
|
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| ( | ||
| item, | ||
| if from_version == &0 { | ||
| // Version zero is special as initializing from genesis always gets us latest. | ||
| quote! { if version == #from_version { Self::#ident(genesis); version = Self::VERSION; } } | ||
| } else { | ||
| // For other versions, each migration brings us from V to V+1. | ||
| quote! { if version == #from_version { Self::#ident(); version += 1; } } | ||
| } | ||
| ) | ||
| }).unzip(); | ||
|
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| // Ensure there is a genesis migration, at least an empty one that bumps the version. | ||
| if !seen_versions.contains(&0) { | ||
| migrate_arms.push(quote! { | ||
| if version == 0u32 { version = Self::VERSION; } | ||
| }); | ||
| } | ||
|
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| quote! { | ||
| #[automatically_derived] | ||
| impl #generics sdk::module::MigrationHandler for #ty { | ||
| #genesis_ty | ||
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| fn init_or_migrate<C: Context>( | ||
| _ctx: &mut C, | ||
| meta: &mut sdk::modules::core::types::Metadata, | ||
| genesis: Self::Genesis, | ||
| ) -> bool { | ||
| let mut version = meta.versions.get(Self::NAME).copied().unwrap_or_default(); | ||
| if version == Self::VERSION { | ||
| return false; // Already the latest version. | ||
| } | ||
|
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| #(#migrate_arms)* | ||
|
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| if version != Self::VERSION { | ||
| panic!("no migration for module state from version {version} to {}", Self::VERSION) | ||
| } | ||
|
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| // Update version information. | ||
| meta.versions.insert(Self::NAME.to_owned(), Self::VERSION); | ||
| return true; | ||
| } | ||
| } | ||
|
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| #[automatically_derived] | ||
| impl #generics #ty { | ||
| #(#migrate_fns)* | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
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| #[derive(Debug, Clone, PartialEq)] | ||
| struct MigrationHandlerAttr { | ||
| /// Version that this handler handles. Zero indicates genesis. | ||
| from_version: u32, | ||
| } | ||
| impl syn::parse::Parse for MigrationHandlerAttr { | ||
| fn parse(input: syn::parse::ParseStream<'_>) -> syn::Result<Self> { | ||
| let kind: syn::Ident = input.parse()?; | ||
| let from_version = match kind.to_string().as_str() { | ||
| "init" => 0, | ||
| "from" => { | ||
| let _: syn::token::Eq = input.parse()?; | ||
| let version: syn::LitInt = input.parse()?; | ||
|
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| version.base10_parse()? | ||
| } | ||
| _ => return Err(syn::Error::new(kind.span(), "invalid migration kind")), | ||
| }; | ||
|
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| if !input.is_empty() { | ||
| return Err(syn::Error::new(input.span(), "unexpected extra tokens")); | ||
| } | ||
| Ok(Self { from_version }) | ||
| } | ||
| } | ||
|
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| fn parse_attrs(attrs: &[syn::Attribute]) -> Option<MigrationHandlerAttr> { | ||
| let migration_meta = attrs | ||
| .iter() | ||
| .find(|attr| attr.path().is_ident("migration"))?; | ||
| migration_meta | ||
| .parse_args() | ||
| .map_err(|err| { | ||
| emit_compile_error(format!( | ||
| "Unsupported format of #[migration(...)] attribute: {err}" | ||
| )) | ||
| }) | ||
| .ok() | ||
| } |
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