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xso-proc: add support for text codecs

Browse source 
Text codecs allow to customize the conversion of data from/to XML,
in particular in two scenarios:

1. When the type for which the behaviour is to be defined comes from a
   foreign crate, preventing the implementation of
   FromXmlText/IntoXmlText.

2. When there is not one obvious, or more than one sensible, way to
   convert a value to XML text and back.
This commit is contained in:
Jonas Schäfer 2024-06-26 18:26:13 +02:00
commit c83ff286e0
8 changed files with 258 additions and 26 deletions
Download patch file Download diff file Expand all files Collapse all files

4
xso-proc/src/compound.rs
View file

@ -280,9 +280,9 @@ impl Compound {
State::new(state_name)
.with_field(&bound_name, field.ty())
.with_impl(quote! {
::core::option::Option::Some(::xso::exports::rxml::Event::Text(
#generator.map(|value| ::xso::exports::rxml::Event::Text(
::xso::exports::rxml::parser::EventMetrics::zero(),
#generator,
value,
))
}),
);

46
xso-proc/src/field.rs
View file

@ -17,6 +17,7 @@ use crate::meta::{Flag, NameRef, NamespaceRef, XmlFieldMeta};
use crate::scope::{FromEventsScope, IntoEventsScope};
use crate::types::{
default_fn, from_xml_text_fn, into_optional_xml_text_fn, into_xml_text_fn, string_ty,
text_codec_decode_fn, text_codec_encode_fn,
};
/// Code slices necessary for declaring and initializing a temporary variable
@ -98,7 +99,10 @@ enum FieldKind {
},
/// The field maps to the character data of the element.
Text,
Text {
/// Optional codec to use
codec: Option<Type>,
},
}
impl FieldKind {
@ -143,7 +147,7 @@ impl FieldKind {
})
}
XmlFieldMeta::Text => Ok(Self::Text),
XmlFieldMeta::Text { codec } => Ok(Self::Text { codec }),
}
}
}
@ -257,10 +261,21 @@ impl FieldDef {
})
}
FieldKind::Text => {
FieldKind::Text { ref codec } => {
let FromEventsScope { ref text, .. } = scope;
let field_access = scope.access_field(&self.member);
let from_xml_text = from_xml_text_fn(self.ty.clone());
let finalize = match codec {
Some(codec_ty) => {
let decode = text_codec_decode_fn(codec_ty.clone(), self.ty.clone());
quote! {
#decode(#field_access)?
}
}
None => {
let from_xml_text = from_xml_text_fn(self.ty.clone());
quote! { #from_xml_text(#field_access)? }
}
};
Ok(FieldBuilderPart::Text {
value: FieldTempInit {
@ -270,9 +285,7 @@ impl FieldDef {
collect: quote! {
#field_access.push_str(#text.as_str());
},
finalize: quote! {
#from_xml_text(#field_access)?
},
finalize,
})
}
}
@ -318,14 +331,19 @@ impl FieldDef {
})
}
FieldKind::Text => {
let into_xml_text = into_xml_text_fn(self.ty.clone());
FieldKind::Text { ref codec } => {
let generator = match codec {
Some(codec_ty) => {
let encode = text_codec_encode_fn(codec_ty.clone(), self.ty.clone());
quote! { #encode(#bound_name)? }
}
None => {
let into_xml_text = into_xml_text_fn(self.ty.clone());
quote! { ::core::option::Option::Some(#into_xml_text(#bound_name)?) }
}
};
Ok(FieldIteratorPart::Text {
generator: quote! {
#into_xml_text(#bound_name)?
},
})
Ok(FieldIteratorPart::Text { generator })
}
}
}

29
xso-proc/src/meta.rs
View file

@ -312,7 +312,10 @@ pub(crate) enum XmlFieldMeta {
},
/// `#[xml(text)]`
Text,
Text {
/// The path to the optional codec type.
codec: Option<Type>,
},
}
impl XmlFieldMeta {
@ -393,8 +396,28 @@ impl XmlFieldMeta {
}
/// Parse a `#[xml(text)]` meta.
fn text_from_meta(_: ParseNestedMeta<'_>) -> Result<Self> {
Ok(Self::Text)
fn text_from_meta(meta: ParseNestedMeta<'_>) -> Result<Self> {
let mut codec: Option<Type> = None;
if meta.input.peek(Token![=]) {
Ok(Self::Text {
codec: Some(meta.value()?.parse()?),
})
} else if meta.input.peek(syn::token::Paren) {
meta.parse_nested_meta(|meta| {
if meta.path.is_ident("codec") {
if codec.is_some() {
return Err(Error::new_spanned(meta.path, "duplicate `codec` key"));
}
codec = Some(meta.value()?.parse()?);
Ok(())
} else {
Err(Error::new_spanned(meta.path, "unsupported key"))
}
})?;
Ok(Self::Text { codec })
} else {
Ok(Self::Text { codec: None })
}
}
/// Parse [`Self`] from a nestd meta, switching on the identifier

73
xso-proc/src/types.rs
View file

@ -220,3 +220,76 @@ pub(crate) fn into_xml_text_fn(ty: Type) -> Expr {
},
})
}
/// Construct a [`syn::TypePath`] referring to
/// `<#codec_ty as ::xso::TextCodec::<#for_ty>>` and return the
/// [`syn::Span`] of the `codec_ty` alongside it.
fn text_codec_of(codec_ty: Type, for_ty: Type) -> (Span, TypePath) {
let span = codec_ty.span();
(
span,
TypePath {
qself: Some(QSelf {
lt_token: syn::token::Lt { spans: [span] },
ty: Box::new(codec_ty),
position: 2,
as_token: Some(syn::token::As { span }),
gt_token: syn::token::Gt { spans: [span] },
}),
path: Path {
leading_colon: Some(syn::token::PathSep {
spans: [span, span],
}),
segments: [
PathSegment {
ident: Ident::new("xso", span),
arguments: PathArguments::None,
},
PathSegment {
ident: Ident::new("TextCodec", span),
arguments: PathArguments::AngleBracketed(AngleBracketedGenericArguments {
colon2_token: Some(syn::token::PathSep {
spans: [span, span],
}),
lt_token: syn::token::Lt { spans: [span] },
args: [GenericArgument::Type(for_ty)].into_iter().collect(),
gt_token: syn::token::Gt { spans: [span] },
}),
},
]
.into_iter()
.collect(),
},
},
)
}
/// Construct a [`syn::Expr`] referring to
/// `<#codec_ty as ::xso::TextCodec::<#for_ty>>::encode`.
pub(crate) fn text_codec_encode_fn(codec_ty: Type, for_ty: Type) -> Expr {
let (span, mut ty) = text_codec_of(codec_ty, for_ty);
ty.path.segments.push(PathSegment {
ident: Ident::new("encode", span),
arguments: PathArguments::None,
});
Expr::Path(ExprPath {
attrs: Vec::new(),
qself: ty.qself,
path: ty.path,
})
}
/// Construct a [`syn::Expr`] referring to
/// `<#codec_ty as ::xso::TextCodec::<#for_ty>>::decode`.
pub(crate) fn text_codec_decode_fn(codec_ty: Type, for_ty: Type) -> Expr {
let (span, mut ty) = text_codec_of(codec_ty, for_ty);
ty.path.segments.push(PathSegment {
ident: Ident::new("decode", span),
arguments: PathArguments::None,
});
Expr::Path(ExprPath {
attrs: Vec::new(),
qself: ty.qself,
path: ty.path,
})
}