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Some initial work on xml parsing
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Lennart
278
crates/xml/derive/src/de/de_struct.rs
Normal file
278
crates/xml/derive/src/de/de_struct.rs
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@@ -0,0 +1,278 @@
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use super::attrs::{parse_field_attrs, parse_struct_attrs, FieldAttrs};
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use core::panic;
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use heck::ToKebabCase;
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use proc_macro2::Span;
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use quote::quote;
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use syn::{AngleBracketedGenericArguments, DataStruct, DeriveInput, TypePath};
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fn get_generic_type(ty: &syn::Type) -> Option<&syn::Type> {
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if let syn::Type::Path(TypePath { path, .. }) = ty {
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if let Some(seg) = path.segments.last() {
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if let syn::PathArguments::AngleBracketed(AngleBracketedGenericArguments {
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args, ..
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}) = &seg.arguments
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{
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if let Some(syn::GenericArgument::Type(t)) = &args.first() {
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return Some(t);
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}
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}
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}
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}
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None
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}
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pub struct Field {
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pub field: syn::Field,
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pub attrs: FieldAttrs,
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}
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impl Field {
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fn from_syn_field(field: syn::Field) -> Self {
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Self {
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attrs: parse_field_attrs(&field.attrs),
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field,
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}
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}
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fn de_name(&self) -> String {
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self.attrs
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.rename
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.to_owned()
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.unwrap_or(self.field_ident().to_string().to_kebab_case())
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}
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fn field_ident(&self) -> &syn::Ident {
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self.field
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.ident
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.as_ref()
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.expect("tuple structs not supported")
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}
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fn ty(&self) -> &syn::Type {
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&self.field.ty
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}
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fn builder_field(&self) -> proc_macro2::TokenStream {
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let field_ident = self.field_ident();
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let ty = self.ty();
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if self.attrs.default.is_some() {
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quote! {
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#field_ident: #ty,
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}
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} else if self.attrs.flatten {
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let generic_type = get_generic_type(ty).expect("flatten attribute only implemented for explicit generics (rustical_xml will assume the first generic as the inner type)");
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quote! {
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#field_ident: Vec<#generic_type>,
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}
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} else {
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quote! {
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#field_ident: Option<#ty>,
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}
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}
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}
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fn builder_field_init(&self) -> proc_macro2::TokenStream {
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let field_ident = self.field_ident();
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if let Some(default) = &self.attrs.default {
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quote! {
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#field_ident: #default(),
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}
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} else if self.attrs.flatten {
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quote! {
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#field_ident: vec![],
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}
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} else {
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quote! {
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#field_ident: None,
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}
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}
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}
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fn builder_field_build(&self) -> proc_macro2::TokenStream {
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let field_ident = self.field_ident();
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if self.attrs.flatten {
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quote! {
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#field_ident: FromIterator::from_iter(builder.#field_ident.into_iter())
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}
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} else if self.attrs.default.is_some() {
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quote! {
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#field_ident: builder.#field_ident,
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}
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} else {
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quote! {
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#field_ident: builder.#field_ident.expect("todo: handle missing field"),
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}
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}
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}
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fn named_branch(&self) -> Option<proc_macro2::TokenStream> {
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if self.attrs.text {
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return None;
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}
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if self.attrs.untagged {
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return None;
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}
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let field_name = syn::LitByteStr::new(self.de_name().as_bytes(), Span::call_site());
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let field_ident = self.field_ident();
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let deserializer = self.ty();
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Some(if self.attrs.default.is_some() {
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quote! {
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#field_name => {
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builder.#field_ident = <#deserializer as rustical_xml::XmlDeserialize>::deserialize(reader, &start, empty)?;
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},
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}
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} else if self.attrs.flatten {
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let deserializer = get_generic_type(self.ty()).expect("flatten attribute only implemented for explicit generics (rustical_xml will assume the first generic as the inner type)");
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quote! {
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#field_name => {
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builder.#field_ident.push(<#deserializer as rustical_xml::XmlDeserialize>::deserialize(reader, &start, empty)?);
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},
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}
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} else {
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quote! {
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#field_name => {
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builder.#field_ident = Some(<#deserializer as rustical_xml::XmlDeserialize>::deserialize(reader, &start, empty)?);
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},
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}
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})
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}
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fn untagged_branch(&self) -> Option<proc_macro2::TokenStream> {
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if !self.attrs.untagged {
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return None;
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}
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let field_ident = self.field_ident();
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let deserializer = self.ty();
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Some(quote! {
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_ => {
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builder.#field_ident = Some(<#deserializer as rustical_xml::XmlDeserialize>::deserialize(reader, &start, empty)?);
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},
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})
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}
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fn text_branch(&self) -> Option<proc_macro2::TokenStream> {
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if !self.attrs.text {
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return None;
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}
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let field_ident = self.field_ident();
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Some(quote! {
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builder.#field_ident = Some(text.to_owned().into());
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})
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}
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}
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pub fn impl_de_struct(input: &DeriveInput, data: &DataStruct) -> proc_macro2::TokenStream {
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let (impl_generics, type_generics, where_clause) = input.generics.split_for_impl();
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let name = &input.ident;
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let struct_attrs = parse_struct_attrs(&input.attrs);
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let fields: Vec<_> = data
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.fields
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.iter()
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.map(|field| Field::from_syn_field(field.to_owned()))
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.collect();
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let builder_fields = fields.iter().map(Field::builder_field);
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let builder_field_inits = fields.iter().map(Field::builder_field_init);
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let named_field_branches = fields.iter().filter_map(Field::named_branch);
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let untagged_field_branches: Vec<_> =
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fields.iter().filter_map(Field::untagged_branch).collect();
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if untagged_field_branches.len() > 1 {
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panic!("Currently only one untagged field supported!");
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}
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let text_field_branches = fields.iter().filter_map(Field::text_branch);
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let builder_field_builds = fields.iter().map(Field::builder_field_build);
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let xml_root_impl = if let Some(root) = struct_attrs.root {
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quote! {
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impl #impl_generics ::rustical_xml::XmlRoot for #name #type_generics #where_clause {
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fn root_tag() -> &'static [u8] {
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#root
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}
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}
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}
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} else {
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quote! {}
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};
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quote! {
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#xml_root_impl
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impl #impl_generics ::rustical_xml::XmlDeserialize for #name #type_generics #where_clause {
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fn deserialize<R: std::io::BufRead>(
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reader: &mut quick_xml::NsReader<R>,
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start: &quick_xml::events::BytesStart,
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empty: bool
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) -> Result<Self, rustical_xml::XmlError> {
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use quick_xml::events::Event;
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use rustical_xml::XmlError;
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let mut buf = Vec::new();
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// initialise fields
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struct StructBuilder {
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#(#builder_fields)*
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}
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let mut builder = StructBuilder {
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#(#builder_field_inits)*
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};
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if !empty {
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loop {
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let event = reader.read_event_into(&mut buf)?;
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match &event {
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Event::End(e) if e.name() == start.name() => {
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break;
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}
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Event::Eof => return Err(XmlError::Eof),
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// start of a child element
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Event::Start(start) | Event::Empty(start) => {
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let empty = matches!(event, Event::Empty(_));
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let (_ns, name) = reader.resolve_element(start.name());
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match name.as_ref() {
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#(#named_field_branches)*
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#(#untagged_field_branches)*
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_ => {
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// invalid field name
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return Err(XmlError::UnknownError)
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}
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}
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}
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Event::Text(bytes_text) => {
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let text = bytes_text.unescape()?;
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#(#text_field_branches)*
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}
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Event::CData(cdata) => {
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return Err(XmlError::UnsupportedEvent("CDATA"));
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}
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Event::Comment(_) => {
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// ignore
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}
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Event::Decl(_) => {
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// Error: not supported
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return Err(XmlError::UnsupportedEvent("Declaration"));
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}
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Event::PI(_) => {
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// Error: not supported
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return Err(XmlError::UnsupportedEvent("Processing instruction"));
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}
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Event::DocType(doctype) => {
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// Error: start of new document
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return Err(XmlError::UnsupportedEvent("Doctype in the middle of the document"));
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}
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Event::End(end) => {
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// Error: premature end
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return Err(XmlError::Other("Unexpected closing tag for wrong element".to_owned()));
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}
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}
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}
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}
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Ok(Self {
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#(#builder_field_builds)*
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})
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}
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}
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}
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}
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