difftreelog
Merge pull request #434 from UniqueNetwork/doc/struct-versioning
in: master
Doc/struct versioning
2 files changed
crates/struct-versioning/README.mddiffbeforeafterboth--- /dev/null
+++ b/crates/struct-versioning/README.md
@@ -0,0 +1,62 @@
+# struct-versioning
+
+The crate contains procedural macros for versioning data structures.
+Macros [`versioned`] generate versioned variants of a struct.
+
+Example:
+```
+# use struct_versioning::versioned;
+#[versioned(version = 5, first_version = 2)]
+struct Example {}
+
+// versioned macro will generate suffixed versions of example struct,
+// starting from `Version{first_version or 1}` to `Version{version}` inclusive
+let _ver2 = ExampleVersion2 {};
+let _ver3 = ExampleVersion3 {};
+let _ver4 = ExampleVersion4 {};
+let _ver5 = ExampleVersion5 {};
+
+// last version will also be aliased with original struct name
+let _orig: Example = ExampleVersion5 {};
+
+#[versioned(version = 2, upper)]
+#[derive(PartialEq, Debug)]
+struct Upper {
+ #[version(..2)]
+ removed: u32,
+ #[version(2.., upper(10))]
+ added: u32,
+
+ #[version(..2)]
+ retyped: u32,
+ #[version(2.., upper(retyped as u64))]
+ retyped: u64,
+}
+
+// #[version] attribute on field allows to specify, in which versions of structs this field should present
+// versions here works as standard rust ranges, start is inclusive, end is exclusive
+let _up1 = UpperVersion1 {removed: 1, retyped: 0};
+let _up2 = UpperVersion2 {added: 1, retyped: 0};
+
+// and upper() allows to specify, which value should be assigned to this field in `From<OldVersion>` impl
+assert_eq!(
+ UpperVersion2::from(UpperVersion1 {removed: 0, retyped: 6}),
+ UpperVersion2 {added: 10, retyped: 6},
+);
+```
+
+In this case, the upgrade is described in `on_runtime_upgrade` using the `translate_values` substrate feature
+
+```ignore
+#[pallet::hooks]
+impl<T: Config> Hooks<BlockNumberFor<T>> for Pallet<T> {
+ fn on_runtime_upgrade() -> Weight {
+ if StorageVersion::get::<Pallet<T>>() < StorageVersion::new(1) {
+ <TokenData<T>>::translate_values::<ItemDataVersion1, _>(|v| {
+ Some(<ItemDataVersion2>::from(v))
+ })
+ }
+ 0
+ }
+}
+```
crates/struct-versioning/src/lib.rsdiffbeforeafterboth1use proc_macro::TokenStream;2use quote::format_ident;3use syn::{4 parse::{Parse, ParseStream},5 Token, LitInt, parse_macro_input, ItemStruct, Error, Fields, Result, Field, Expr,6 parenthesized,7};8use quote::quote;910mod kw {11 syn::custom_keyword!(version);12 syn::custom_keyword!(first_version);13 syn::custom_keyword!(versions);14 syn::custom_keyword!(upper);15}1617struct VersionedAttrs {18 current_version: u32,19 first_version: u32,20 upper: bool,21}2223/// #[versioned(version = 2)]24impl Parse for VersionedAttrs {25 fn parse(input: ParseStream) -> Result<Self> {26 let mut current_version = None::<u32>;27 let mut first_version = None::<u32>;28 let mut upper = false;2930 loop {31 if input.is_empty() {32 break;33 }34 let lookahead = input.lookahead1();35 if lookahead.peek(kw::version) {36 input.parse::<kw::version>()?;37 input.parse::<Token![=]>()?;38 let t = input.parse::<LitInt>()?;39 if current_version.is_some() {40 return Err(Error::new_spanned(t, "version is already set"));41 }42 current_version = Some(t.base10_parse()?)43 } else if lookahead.peek(kw::first_version) {44 input.parse::<kw::first_version>()?;45 input.parse::<Token![=]>()?;46 let t = input.parse::<LitInt>()?;47 if first_version.is_some() {48 return Err(Error::new_spanned(t, "first version is already set"));49 }50 first_version = Some(t.base10_parse()?)51 } else if lookahead.peek(kw::upper) {52 input.parse::<kw::upper>()?;53 upper = true;54 } else {55 return Err(lookahead.error());56 }5758 if input.is_empty() {59 break;60 } else if input.peek(Token![,]) {61 input.parse::<Token![,]>()?;62 continue;63 } else {64 return Err(input.error("unexpected token"));65 }66 }67 let first_version = first_version.unwrap_or(1);68 let current_version = current_version.unwrap_or(first_version);6970 if current_version == 0 || first_version == 0 || first_version > current_version {71 return Err(Error::new(input.span(), "1 <= first_version <= version"));72 }7374 Ok(Self {75 current_version,76 first_version,77 upper,78 })79 }80}8182/// #[version(..3)] - field vas removed in version 3 (i.e it was exist on version 2, but doesn't on version 3)83/// #[version(3..)] - field has appeared in version 384/// #[version(2..4)] - field was on versions 2, 385/// #[version(1..2, upper(old_field + 1))] - when updating struct from old version to new - calculate new field value from passed expression86struct VersionAttr {87 since: u32,88 before: Option<u32>,8990 upper: Option<Expr>,91}92impl VersionAttr {93 fn exists_on(&self, version: u32) -> bool {94 version >= self.since && self.before.map_or(true, |before| version < before)95 }96}97impl Parse for VersionAttr {98 fn parse(input: ParseStream) -> Result<Self> {99 let mut since = None::<u32>;100 let mut before = None::<u32>;101 let lookahead = input.lookahead1();102103 if lookahead.peek(LitInt) {104 let t: LitInt = input.parse()?;105 since = Some(t.base10_parse()?);106 } else if !lookahead.peek(Token![..]) {107 return Err(lookahead.error());108 }109 let range = input.parse::<Token![..]>()?;110 let lookahead = input.lookahead1();111 if lookahead.peek(LitInt) {112 let t: LitInt = input.parse()?;113 before = Some(t.base10_parse()?);114 } else if !input.is_empty() && !lookahead.peek(Token![,]) {115 return Err(lookahead.error());116 }117118 let upper = if input.peek(Token![,]) {119 input.parse::<Token![,]>()?;120 input.parse::<kw::upper>()?;121 let expr;122 parenthesized!(expr in input);123124 Some(Expr::parse(&expr)?)125 } else {126 None127 };128129 if since.is_none() && before.is_none() {130 return Err(Error::new_spanned(131 range,132 "noop range, remove this version attribute",133 ));134 }135 Ok(Self {136 since: since.unwrap_or(1),137 before,138 upper,139 })140 }141}142impl Default for VersionAttr {143 fn default() -> Self {144 Self {145 since: 1,146 before: None,147 upper: None,148 }149 }150}151152/// Generate versioned variants of a struct153///154/// `#[versioned(version = 1[, first_version = 1][, upper][, versions])]`155/// - *version* - current version of a struct156/// - *first_version* - allows to skip generation of structs, which predates first supported version157/// - *upper* - generate From impls, which converts old version of structs to new158/// - *versions* - generate enum, which contains all possible versions of struct159///160/// Each field may have version attribute161/// `#[version([1]..[2][, upper(old)])]`162/// - *1* - version, on which this field is appeared163/// - *2* - version, in which this field was removed164/// (i.e if set to 2, this field was exist on version 1, and no longer exist on version 2)165/// - *upper* - code, which should be executed to transform old value to new/create new value166#[proc_macro_attribute]167pub fn versioned(attr: TokenStream, input: TokenStream) -> TokenStream {168 let attr = parse_macro_input!(attr as VersionedAttrs);169 let input = parse_macro_input!(input as ItemStruct);170171 let fields = match input.fields {172 Fields::Named(named) => named.named,173 _ => {174 return Error::new_spanned(input, "expected named fields")175 .into_compile_error()176 .into()177 }178 };179 let fields = fields180 .iter()181 .map(|field| {182 let version_attr = match field.attrs.iter().find(|a| a.path.is_ident("version")) {183 Some(v) => v.parse_args::<VersionAttr>()?,184 None => return Ok((VersionAttr::default(), field.clone())),185 };186 let mut field = field.clone();187 field.attrs.retain(|a| !a.path.is_ident("version"));188 Ok((version_attr, field))189 })190 .collect::<Result<Vec<(VersionAttr, Field)>>>();191 let fields = match fields {192 Ok(f) => f,193 Err(e) => return e.into_compile_error().into(),194 };195196 let attrs = input.attrs;197 let vis = input.vis;198 let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();199 let mut out = Vec::new();200 for version in attr.first_version..=attr.current_version {201 let name = if version == attr.current_version {202 input.ident.clone()203 } else {204 format_ident!("{}Version{}", &input.ident, version)205 };206 let current_fields = fields207 .iter()208 .filter_map(|(ver, field)| ver.exists_on(version).then(|| field));209210 let mut doc = Vec::new();211 if version > attr.first_version {212 doc.push(" # Versioning".into());213 doc.push(format!(" Changes between {} and {}:", version - 1, version));214 for (ver, field) in fields.iter() {215 match (ver.exists_on(version - 1), ver.exists_on(version)) {216 (true, false) => {217 let ty = &field.ty;218 doc.push(format!(219 " - {}: {} was removed",220 field.ident.as_ref().unwrap(),221 quote! {#ty}222 ))223 }224 (false, true) => {225 let ty = &field.ty;226 doc.push(format!(227 " - [`{}`]: {} was added",228 field.ident.as_ref().unwrap(),229 quote! {#ty}230 ))231 }232 _ => {}233 }234 }235 }236237 let upper = if attr.upper && version > attr.first_version {238 let prev_version = format_ident!("{}Version{}", &input.ident, version - 1);239 let removed_fields = fields240 .iter()241 .filter(|(v, _)| v.exists_on(version - 1) && !v.exists_on(version))242 .map(|(_, f)| f.ident.as_ref().unwrap())243 .collect::<Vec<_>>();244 let added_fields = fields245 .iter()246 .filter(|(v, _)| !v.exists_on(version - 1) && v.exists_on(version))247 .map(|(v, f)| {248 let name = f.ident.as_ref().unwrap();249 let value = v.upper.clone().unwrap_or_else(|| {250 Expr::Verbatim(251 Error::new_spanned(f, "missing upper declaration").to_compile_error(),252 )253 });254 quote! { #name: #value }255 });256 let passed_fields = fields257 .iter()258 .filter(|(v, _)| v.exists_on(version - 1) && v.exists_on(version))259 .map(|(_, f)| f.ident.as_ref().unwrap())260 .collect::<Vec<_>>();261 // let added_fields = fields;262 quote! {263 impl #impl_generics From<#prev_version #ty_generics> for #name #ty_generics #where_clause {264 fn from(old: #prev_version #ty_generics) -> Self {265 let #prev_version {266 #(#removed_fields,)*267 #(#passed_fields,)*268 } = old;269 #(let _ = &#removed_fields;)*270 Self {271 #(#added_fields,)*272 #(#passed_fields,)*273 }274 }275 }276 }277 } else {278 quote! {}279 };280281 out.push(quote! {282 #(#attrs)*283 #(#[doc = #doc])*284 #vis struct #name #impl_generics #where_clause {285 #(#current_fields,)*286 }287288 #upper289 });290 }291292 let ident = &input.ident;293 let last_version = format_ident!("{}Version{}", input.ident, attr.current_version);294295 quote! {296 #(#out)*297298 #vis type #last_version #ty_generics = #ident #ty_generics;299 }300 .into()301}