ezno_parser_visitable_derive/
macro.rs

1use proc_macro::TokenStream;
2use std::error::Error;
3use string_cases::StringCasesExt;
4use syn_helpers::{
5	derive_trait,
6	proc_macro2::{Ident, Span},
7	quote,
8	syn::{
9		self, parse_macro_input, parse_quote, DeriveInput, Stmt, __private::quote::format_ident,
10		parse::Parse,
11	},
12	Constructable, FieldMut, HasAttributes, NamedOrUnnamedFieldMut, Trait, TraitItem,
13};
14
15/// On the top structure
16const VISIT_SELF_NAME: &str = "visit_self";
17/// Per field modifiers
18const VISIT_SKIP_NAME: &str = "visit_skip_field";
19/// Add to chain. Can be on item or a field
20const VISIT_WITH_CHAIN_NAME: &str = "visit_with_chain";
21
22/// Usage #[derive(Visitable)]
23#[proc_macro_derive(Visitable, attributes(visit_self, visit_skip_field, visit_custom_visit))]
24pub fn generate_visit_implementation(input: TokenStream) -> TokenStream {
25	let input = parse_macro_input!(input as DeriveInput);
26
27	let visit_item = TraitItem::new_method(
28		Ident::new("visit", Span::call_site()),
29		Some(vec![parse_quote!(TData)]),
30		syn_helpers::TypeOfSelf::Reference,
31		vec![
32			parse_quote!(visitors: &mut (impl crate::visiting::VisitorReceiver<TData> + ?Sized)),
33			parse_quote!(data: &mut TData),
34			parse_quote!(options: &crate::VisitOptions),
35			parse_quote!(chain: &mut ::temporary_annex::Annex<crate::visiting::Chain>),
36		],
37		None,
38		|item| generated_visit_item(item, VisitType::Immutable),
39	);
40
41	let visit_mut_item = TraitItem::new_method(
42		Ident::new("visit_mut", Span::call_site()),
43		Some(vec![parse_quote!(TData)]),
44		syn_helpers::TypeOfSelf::MutableReference,
45		vec![
46			parse_quote!(visitors: &mut (impl crate::visiting::VisitorMutReceiver<TData> + ?Sized)),
47			parse_quote!(data: &mut TData),
48			parse_quote!(options: &crate::VisitOptions),
49			parse_quote!(chain: &mut ::temporary_annex::Annex<crate::visiting::Chain>),
50		],
51		None,
52		|item| generated_visit_item(item, VisitType::Mutable),
53	);
54
55	let visitable_trait = Trait {
56		name: parse_quote!(crate::visiting::Visitable),
57		generic_parameters: None,
58		items: vec![visit_item, visit_mut_item],
59	};
60
61	let output = derive_trait(input, visitable_trait);
62
63	output.into()
64}
65
66#[derive(Clone, Copy)]
67enum VisitType {
68	Immutable,
69	Mutable,
70}
71
72fn generated_visit_item(
73	mut item: syn_helpers::Item,
74	visit_type: VisitType,
75) -> Result<Vec<Stmt>, Box<dyn Error>> {
76	let attributes = item.structure.get_attributes();
77
78	let visit_self = attributes.iter().find_map(|attr| {
79		attr.path().is_ident(VISIT_SELF_NAME).then_some({
80			let mut ident = None::<Ident>;
81			let res = attr.parse_nested_meta(|meta| {
82				if meta.path.is_ident("under") {
83					let value = meta.value()?;
84					ident = value.parse()?;
85					Ok(())
86				} else {
87					Err(meta.error("expected `under=...`"))
88				}
89			});
90			if res.is_ok() {
91				Some(ident.unwrap())
92			} else {
93				// TODO
94				None
95			}
96		})
97	});
98
99	let visit_with_chain: Option<syn::Expr> = attributes
100		.iter()
101		.find_map(|attr| {
102			attr.path().is_ident(VISIT_WITH_CHAIN_NAME).then_some(attr.parse_args().ok())
103		})
104		.flatten();
105
106	let mut lines = Vec::new();
107
108	if let Some(expr_tokens) = visit_with_chain {
109		lines.push(parse_quote!( let mut chain = &mut chain.push_annex(#expr_tokens); ))
110	}
111
112	if let Some(under) = visit_self {
113		let mut_postfix =
114			matches!(visit_type, VisitType::Mutable).then_some("_mut").unwrap_or_default();
115
116		if let Some(under) = under {
117			let func_name = format_ident!("visit_{}{}", under, mut_postfix);
118			lines.push(parse_quote!(visitors.#func_name(self.into(), data,  chain); ))
119		} else {
120			let struct_name_as_snake_case = &item.structure.get_name().to_string().to_snake_case();
121			let func_name = format_ident!("visit_{}{}", struct_name_as_snake_case, mut_postfix);
122			lines.push(parse_quote!( visitors.#func_name(self, data,  chain); ))
123		}
124	}
125
126	let mut field_lines = item.map_constructable(|mut constructable| {
127		Ok(constructable
128			.get_fields_mut()
129			.fields_iterator_mut()
130			.flat_map(|mut field: NamedOrUnnamedFieldMut| -> Option<Stmt> {
131				let attributes = field.get_attributes();
132
133				let skip_field_attr =
134					attributes.iter().find(|attr| attr.path().is_ident(VISIT_SKIP_NAME));
135
136				// TODO maybe?
137				// // None == unconditional
138				// let _skip_field_expression: Option<Expr> =
139				// 	skip_field_attr.as_ref().map(|attr| attr.bracket_token);
140
141				let visit_with_chain = attributes.iter().find_map(|attr| {
142					// TODO error rather than flatten
143					attr.path()
144						.is_ident(VISIT_WITH_CHAIN_NAME)
145						.then_some(attr.parse_args_with(syn::Expr::parse).ok())
146						.flatten()
147				});
148
149				let chain = if let Some(expr_tokens) = visit_with_chain {
150					quote!(&mut chain.push_annex(#expr_tokens))
151				} else {
152					quote!(chain)
153				};
154
155				if skip_field_attr.is_none() {
156					let reference = field.get_reference();
157					Some(match visit_type {
158						VisitType::Immutable => parse_quote! {
159							crate::Visitable::visit(#reference, visitors, data, options, #chain);
160						},
161						VisitType::Mutable => parse_quote! {
162							crate::Visitable::visit_mut(#reference, visitors, data, options, #chain);
163						},
164					})
165				} else {
166					None
167				}
168			})
169			.collect::<Vec<_>>())
170	})?;
171
172	lines.append(&mut field_lines);
173
174	Ok(lines)
175}
ezno_parser_visitable_derive/macro.rs

ezno_parser_visitable_derive/
macro.rs
