git.delta.rocks / unique-network / refs/commits / 593e55c0dc52

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, 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}