xso_proc/
lib.rs

1// Copyright (c) 2024 Jonas Schäfer <jonas@zombofant.net>
2//
3// This Source Code Form is subject to the terms of the Mozilla Public
4// License, v. 2.0. If a copy of the MPL was not distributed with this
5// file, You can obtain one at http://mozilla.org/MPL/2.0/.
6
7#![forbid(unsafe_code)]
8#![warn(missing_docs)]
9#![allow(rustdoc::private_intra_doc_links)]
10#![cfg_attr(docsrs, feature(doc_auto_cfg))]
11/*!
12# Macros for parsing XML into Rust structs, and vice versa
13
14**If you are a user of `xso_proc` or `xso`, please
15return to `xso` for more information**. The documentation of
16`xso_proc` is geared toward developers of `…_macros` and `…_core`.
17
18**You have been warned.**
19*/
20
21// Wondering about RawTokenStream vs. TokenStream?
22// syn mostly works with proc_macro2, while the proc macros themselves use
23// proc_macro.
24use proc_macro::TokenStream as RawTokenStream;
25use proc_macro2::{Span, TokenStream};
26use quote::quote;
27use syn::*;
28
29mod common;
30mod compound;
31mod enums;
32mod error_message;
33mod field;
34mod meta;
35mod scope;
36mod state;
37mod structs;
38mod types;
39
40use common::{AsXmlParts, FromXmlParts, ItemDef};
41
42/// Convert an [`syn::Item`] into the parts relevant for us.
43///
44/// If the item is of an unsupported variant, an appropriate error is
45/// returned.
46fn parse_struct(item: Item) -> Result<(Visibility, Ident, Box<dyn ItemDef>)> {
47    match item {
48        Item::Struct(item) => {
49            let meta = meta::XmlCompoundMeta::parse_from_attributes(&item.attrs)?;
50            let def = structs::StructDef::new(&item.ident, meta, &item.fields)?;
51            Ok((item.vis, item.ident, Box::new(def)))
52        }
53        Item::Enum(item) => {
54            let meta = meta::XmlCompoundMeta::parse_from_attributes(&item.attrs)?;
55            let def = enums::EnumDef::new(&item.ident, meta, &item.variants)?;
56            Ok((item.vis, item.ident, Box::new(def)))
57        }
58        other => Err(Error::new_spanned(other, "cannot derive on this item")),
59    }
60}
61
62/// Generate a `xso::FromXml` implementation for the given item, or fail with
63/// a proper compiler error.
64fn from_xml_impl(input: Item) -> Result<TokenStream> {
65    let (vis, ident, def) = parse_struct(input)?;
66
67    let name_ident = Ident::new("name", Span::call_site());
68    let attrs_ident = Ident::new("attrs", Span::call_site());
69
70    let FromXmlParts {
71        defs,
72        from_events_body,
73        builder_ty_ident,
74    } = def.make_from_events_builder(&vis, &name_ident, &attrs_ident)?;
75
76    #[cfg_attr(not(feature = "minidom"), allow(unused_mut))]
77    let mut result = quote! {
78        #defs
79
80        impl ::xso::FromXml for #ident {
81            type Builder = #builder_ty_ident;
82
83            fn from_events(
84                name: ::xso::exports::rxml::QName,
85                attrs: ::xso::exports::rxml::AttrMap,
86            ) -> ::core::result::Result<Self::Builder, ::xso::error::FromEventsError> {
87                #from_events_body
88            }
89        }
90    };
91
92    #[cfg(feature = "minidom")]
93    result.extend(quote! {
94        impl ::core::convert::TryFrom<::xso::exports::minidom::Element> for #ident {
95            type Error = ::xso::error::FromElementError;
96
97            fn try_from(other: ::xso::exports::minidom::Element) -> ::core::result::Result<Self, Self::Error> {
98                ::xso::try_from_element(other)
99            }
100        }
101    });
102
103    if def.debug() {
104        println!("{}", result);
105    }
106
107    Ok(result)
108}
109
110/// Macro to derive a `xso::FromXml` implementation on a type.
111///
112/// The user-facing documentation for this macro lives in the `xso` crate.
113#[proc_macro_derive(FromXml, attributes(xml))]
114pub fn from_xml(input: RawTokenStream) -> RawTokenStream {
115    // Shim wrapper around `from_xml_impl` which converts any errors into
116    // actual compiler errors within the resulting token stream.
117    let item = syn::parse_macro_input!(input as Item);
118    match from_xml_impl(item) {
119        Ok(v) => v.into(),
120        Err(e) => e.into_compile_error().into(),
121    }
122}
123
124/// Generate a `xso::AsXml` implementation for the given item, or fail with
125/// a proper compiler error.
126fn as_xml_impl(input: Item) -> Result<TokenStream> {
127    let (vis, ident, def) = parse_struct(input)?;
128
129    let AsXmlParts {
130        defs,
131        as_xml_iter_body,
132        item_iter_ty_lifetime,
133        item_iter_ty,
134    } = def.make_as_xml_iter(&vis)?;
135
136    #[cfg_attr(not(feature = "minidom"), allow(unused_mut))]
137    let mut result = quote! {
138        #defs
139
140        impl ::xso::AsXml for #ident {
141            type ItemIter<#item_iter_ty_lifetime> = #item_iter_ty;
142
143            fn as_xml_iter(&self) -> ::core::result::Result<Self::ItemIter<'_>, ::xso::error::Error> {
144                #as_xml_iter_body
145            }
146        }
147    };
148
149    #[cfg(all(feature = "minidom", feature = "panicking-into-impl"))]
150    result.extend(quote! {
151        impl ::core::convert::From<#ident> for ::xso::exports::minidom::Element {
152            fn from(other: #ident) -> Self {
153                ::xso::transform(&other).expect("seamless conversion into minidom::Element")
154            }
155        }
156
157        impl ::core::convert::From<&#ident> for ::xso::exports::minidom::Element {
158            fn from(other: &#ident) -> Self {
159                ::xso::transform(other).expect("seamless conversion into minidom::Element")
160            }
161        }
162    });
163
164    #[cfg(all(feature = "minidom", not(feature = "panicking-into-impl")))]
165    result.extend(quote! {
166        impl ::core::convert::TryFrom<#ident> for ::xso::exports::minidom::Element {
167            type Error = ::xso::error::Error;
168
169            fn try_from(other: #ident) -> ::core::result::Result<Self, Self::Error> {
170                ::xso::transform(&other)
171            }
172        }
173        impl ::core::convert::TryFrom<&#ident> for ::xso::exports::minidom::Element {
174            type Error = ::xso::error::Error;
175
176            fn try_from(other: &#ident) -> ::core::result::Result<Self, Self::Error> {
177                ::xso::transform(other)
178            }
179        }
180    });
181
182    if def.debug() {
183        println!("{}", result);
184    }
185
186    Ok(result)
187}
188
189/// Macro to derive a `xso::AsXml` implementation on a type.
190///
191/// The user-facing documentation for this macro lives in the `xso` crate.
192#[proc_macro_derive(AsXml, attributes(xml))]
193pub fn as_xml(input: RawTokenStream) -> RawTokenStream {
194    // Shim wrapper around `as_xml_impl` which converts any errors into
195    // actual compiler errors within the resulting token stream.
196    let item = syn::parse_macro_input!(input as Item);
197    match as_xml_impl(item) {
198        Ok(v) => v.into(),
199        Err(e) => e.into_compile_error().into(),
200    }
201}
xso_proc/lib.rs

xso_proc/
lib.rs
