1use proc_macro::TokenStream;2use quote::format_ident;3use syn::{4 parse::{Parse, ParseStream},5 Token, LitInt, parse_macro_input, ItemStruct, Error, Fields, Result, Field,6 punctuated::Punctuated, Expr, 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 versions: bool,22}232425impl Parse for VersionedAttrs {26 fn parse(input: ParseStream) -> Result<Self> {27 let mut current_version = None::<u32>;28 let mut first_version = None::<u32>;29 let mut upper = false;30 let mut versions = false;3132 loop {33 if input.is_empty() {34 break;35 }36 let lookahead = input.lookahead1();37 if lookahead.peek(kw::version) {38 input.parse::<kw::version>()?;39 input.parse::<Token![=]>()?;40 let t = input.parse::<LitInt>()?;41 if current_version.is_some() {42 return Err(Error::new_spanned(t, "version is already set"));43 }44 current_version = Some(t.base10_parse()?)45 } else if lookahead.peek(kw::first_version) {46 input.parse::<kw::first_version>()?;47 input.parse::<Token![=]>()?;48 let t = input.parse::<LitInt>()?;49 if first_version.is_some() {50 return Err(Error::new_spanned(t, "first version is already set"));51 }52 first_version = Some(t.base10_parse()?)53 } else if lookahead.peek(kw::upper) {54 input.parse::<kw::upper>()?;55 upper = true;56 } else if lookahead.peek(kw::versions) {57 input.parse::<kw::version>()?;58 versions = true;59 } else {60 return Err(lookahead.error())61 }6263 if input.is_empty() {64 break65 } else if input.peek(Token![,]) {66 input.parse::<Token![,]>()?;67 continue68 } else {69 return Err(input.error("unexpected token"))70 }71 }72 let first_version = first_version.unwrap_or(1);73 let current_version = current_version.unwrap_or(first_version);7475 if current_version == 0 || first_version == 0 || first_version > current_version {76 return Err(Error::new(input.span(), "1 <= first_version <= version"))77 }7879 Ok(Self {80 current_version,81 first_version,82 upper,83 versions,84 })85 }86}878889909192struct VersionAttr {93 since: u32,94 before: Option<u32>,9596 upper: Option<Expr>,97}98impl VersionAttr {99 fn exists_on(&self, version: u32) -> bool {100 version >= self.since && self.before.map_or(true, |before| version < before)101 }102}103impl Parse for VersionAttr {104 fn parse(input: ParseStream) -> Result<Self> {105 let mut since = None::<u32>;106 let mut before = None::<u32>;107 let lookahead = input.lookahead1();108109 if lookahead.peek(LitInt) {110 let t: LitInt = input.parse()?;111 since = Some(t.base10_parse()?);112 } else if !lookahead.peek(Token![..]) {113 return Err(lookahead.error());114 }115 let range = input.parse::<Token![..]>()?;116 let lookahead = input.lookahead1();117 if lookahead.peek(LitInt) {118 let t: LitInt = input.parse()?;119 before = Some(t.base10_parse()?);120 } else if !input.is_empty() && !lookahead.peek(Token![,]) {121 return Err(lookahead.error());122 }123124 let upper = if input.peek(Token![,]) {125 input.parse::<Token![,]>()?;126 input.parse::<kw::upper>()?;127 let expr;128 parenthesized!(expr in input);129130 Some(Expr::parse(&expr)?)131 } else {None};132133 if since.is_none() && before.is_none() {134 return Err(Error::new_spanned(135 range,136 "noop range, remove this version attribute",137 ));138 }139 Ok(Self {140 since: since.unwrap_or(1),141 before,142 upper,143 })144 }145}146impl Default for VersionAttr {147 fn default() -> Self {148 Self {149 since: 1,150 before: None,151 upper: None,152 }153 }154}155156157158159160161162163164165166167168169170#[proc_macro_attribute]171pub fn versioned(attr: TokenStream, input: TokenStream) -> TokenStream {172 let attr = parse_macro_input!(attr as VersionedAttrs);173 let input = parse_macro_input!(input as ItemStruct);174175 let fields = match input.fields {176 Fields::Named(named) => named.named,177 _ => {178 return Error::new_spanned(input, "expected named fields")179 .into_compile_error()180 .into()181 }182 };183 let fields = fields184 .iter()185 .map(|field| {186 let version_attr = match field.attrs.iter().find(|a| a.path.is_ident("version")) {187 Some(v) => v.parse_args::<VersionAttr>()?,188 None => return Ok((VersionAttr::default(), field.clone())),189 };190 let mut field = field.clone();191 field.attrs.retain(|a| !a.path.is_ident("version"));192 Ok((version_attr, field))193 })194 .collect::<Result<Vec<(VersionAttr, Field)>>>();195 let fields = match fields {196 Ok(f) => f,197 Err(e) => return e.into_compile_error().into(),198 };199200 let attrs = input.attrs;201 let vis = input.vis;202 let (impl_generics, ty_generics, where_clause) = input.generics.split_for_impl();203 let mut out = Vec::new();204 for version in attr.first_version..=attr.current_version {205 let name = format_ident!("{}Version{}", &input.ident, version);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!(" - {}: {} was removed", field.ident.as_ref().unwrap(), quote!{#ty}))219 }220 (false, true) => {221 let ty = &field.ty;222 doc.push(format!(" - [`{}`]: {} was added", field.ident.as_ref().unwrap(), quote!{#ty}))223 }224 _ => {},225 }226 }227 }228229 let upper = if attr.upper && version > attr.first_version {230 let prev_version = format_ident!("{}Version{}", &input.ident, version - 1);231 let removed_fields = fields.iter()232 .filter(|(v, _)| v.exists_on(version - 1) && !v.exists_on(version))233 .map(|(_, f)| f.ident.as_ref().unwrap())234 .collect::<Vec<_>>();235 let added_fields = fields.iter()236 .filter(|(v, _)| !v.exists_on(version - 1) && v.exists_on(version))237 .map(|(v, f)| {238 let name = f.ident.as_ref().unwrap();239 let value = v.upper.clone().unwrap_or_else(|| Expr::Verbatim(Error::new_spanned(f, "missing upper declaration").to_compile_error()));240 quote! { #name: #value }241 });242 let passed_fields = fields.iter()243 .filter(|(v, _)| v.exists_on(version - 1) && v.exists_on(version))244 .map(|(_, f)| f.ident.as_ref().unwrap())245 .collect::<Vec<_>>();246 247 quote! {248 impl #impl_generics From<#prev_version #ty_generics> for #name #ty_generics #where_clause {249 fn from(old: #prev_version #ty_generics) -> Self {250 let #prev_version {251 #(#removed_fields,)*252 #(#passed_fields,)*253 } = old;254 #(let _ = &#removed_fields;)*255 Self {256 #(#added_fields,)*257 #(#passed_fields,)*258 }259 }260 }261 }262 } else {quote!{}};263264 out.push(quote! {265 #(#attrs)*266 #(#[doc = #doc])*267 #vis struct #name #impl_generics #where_clause {268 #(#current_fields,)*269 }270271 #upper272 });273 }274275 let ident = &input.ident;276 let last_version = format_ident!("{}Version{}", input.ident, attr.current_version);277278 let versions = if attr.versions {279 let name = format_ident!("{}Versions", input.ident);280 let versions = (attr.first_version..=attr.current_version).map(|v| {281 let var_name = format_ident!("V{}", v);282 let var_type = format_ident!("{}Version{}", input.ident, v);283 quote! {284 #var_name(#var_type),285 }286 });287 let versions = (attr.first_version..=attr.current_version).map(|this_version| {288 let var_name = format_ident!("V{}", this_version);289 let stages = (this_version+1..=attr.current_version).map(|v| {290 let var_type = format_ident!("{}Version{}", input.ident, v);291 quote! {292 let v = #var_type::from(v);293 }294 });295 quote! {296 #var_name(v) => {297 #(#stages)*298 v299 }300 }301 }).collect::<Vec<_>>();302 quote! {303 #vis enum #name {304 #(#versions)*305 }306 impl struct_versioning::Versions for #name {307 type Last = #last_version;308 fn up(self) -> Self::Last {309 match self {310 #(#versions)*311 }312 }313 }314 }315 } else {quote!{}};316317 quote! {318 #(#out)*319320 #vis type #ident #ty_generics = #last_version #ty_generics;321322 #versions323 }324 .into()325}