1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192
#![deny(rustdoc, missing_docs, warnings, clippy::pedantic)] #![allow(missing_doc_code_examples)] #![doc(test(attr(deny(warnings), forbid(unsafe_code))))] #![no_std] //! An attribute macro to apply function-like macros. //! It can apply *multiple* function-like macros that *only* accept an item (do //! *not* accept other function-like macro calls) to a single item or just //! improve the *readability* of the code. //! //! This crate has *no* dependency so you don't need to worry about compile //! time. //! //! # Examples //! ``` //! use apply_macro::apply; //! //! macro_rules! derive_debug { //! { //! #[$attr:meta] // will receive `#[apply(derive_clone, derive_partial_eq)]` //! $input:item //! } => { //! #[$attr] //! #[derive(Debug)] //! $input //! }; //! } //! //! macro_rules! derive_clone { //! { //! #[$attr:meta] // will receive `#[apply(derive_partial_eq)]` //! $input:item //! } => { //! #[$attr] //! #[derive(Clone)] //! $input //! }; //! } //! //! macro_rules! derive_partial_eq { //! ($input:item) => { //! #[derive(PartialEq)] //! $input //! }; //! } //! //! #[apply(derive_debug, derive_clone, derive_partial_eq)] //! struct Num(i32); //! //! assert_eq!(Num(-1).clone(), Num(-1)); //! assert_ne!(Num(1), Num(-1)); //! //! #[apply(derive_debug, derive_clone, derive_partial_eq,)] //! struct TrailingCommaIsAllowed; //! //! assert_eq!(TrailingCommaIsAllowed, TrailingCommaIsAllowed); //! ``` //! //! Single macro example: //! ``` //! use apply_macro::apply; //! //! macro_rules! common_derive { //! ($input:item) => { //! #[derive(Debug, PartialEq)] //! $input //! }; //! } //! //! #[apply(common_derive)] //! struct Num(i32); //! //! assert_eq!(Num(-1), Num(-1)); //! assert_ne!(Num(1), Num(-1)); //! //! #[apply(common_derive,)] //! struct TrailingCommaIsAllowed; //! //! assert_eq!(TrailingCommaIsAllowed, TrailingCommaIsAllowed); //! ``` //! //! The `#[apply(common_derive)]` on `Num` expands to: //! ``` //! # macro_rules! common_derive { //! # ($dummy:item) => {}; //! # } //! common_derive! { //! struct Num(i32); //! } //! ``` //! //! Empty argument is allowed (consistent with `#[derive()]`): //! ``` //! use apply_macro::apply; //! //! #[apply()] //! #[derive()] // consistent //! # #[allow(unused_attributes, dead_code)] //! struct EmptyArg; //! ``` //! //! Although, as a procedural macro, `#[apply]` can't be banned: //! ``` //! # use apply_macro::apply; //! #[apply] // same as `#[apply()]` //! # #[allow(dead_code)] //! struct Oops; //! ``` use core::iter::once; use proc_macro::{Delimiter, Group, Ident, Punct, Spacing, Span, TokenStream, TokenTree}; fn into_tt(tt: impl Into<TokenTree>) -> impl Iterator<Item = TokenTree> { once(tt.into()) } macro_rules! punct { [$punct1:literal $($punct:literal)*] => { into_tt(Punct::new($punct1, Spacing::Joint)) $(.chain(into_tt(Punct::new($punct, Spacing::Joint))))* }; } /// The main attribute macro of this crate. /// /// This macro accepts comma-separated paths to the function-like macros you /// want to call as arguments. See also [examples in the crate-level /// documentation](crate#example). /// /// ## Limitation /// **Note that this may be fixed in the future without a major version bump. /// Do not rely on it.** /// /// This macro does not check for invalid arguments: /// ``` /// use apply_macro::apply; /// /// macro_rules! derive_debug { /// ($input:item) => { /// #[derive(Debug)] /// $input /// }; /// } /// /// #[apply(#[derive(Debug)] struct AnotherStruct; derive_debug)] /// struct ImplsDebug; /// /// dbg!(AnotherStruct, ImplsDebug); /// ``` #[proc_macro_attribute] pub fn apply(args: TokenStream, input: TokenStream) -> TokenStream { if args.is_empty() { input } else { let mut args = args.into_iter(); let mut result = TokenStream::new(); for tt in &mut args { if let TokenTree::Punct(ref punct) = tt { // TODO: https://github.com/rust-lang/rust/pull/78636 if punct.as_char() == ',' { let args: TokenStream = args.collect(); if args.is_empty() { break; } result.extend( punct!['!'].chain(into_tt(Group::new( Delimiter::Brace, punct!['#'] .chain(into_tt(Group::new( Delimiter::Bracket, punct![':' ':'] .chain(into_tt(Ident::new( "apply_macro", Span::call_site(), ))) .chain(punct![':' ':']) .chain(into_tt(Ident::new("apply", Span::call_site()))) .chain(into_tt(Group::new(Delimiter::Parenthesis, args))) .collect(), ))) .chain(input) .collect(), ))), ); return result; } } result.extend(once(tt)); } result.extend(punct!['!'].chain(into_tt(Group::new(Delimiter::Brace, input)))); result } }