xmpp-rs/xso-proc/src/field.rs

873 lines
34 KiB
Rust

// Copyright (c) 2024 Jonas Schäfer <jonas@zombofant.net>
//
// This Source Code Form is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.
//! Compound (struct or enum variant) field types
use proc_macro2::{Span, TokenStream};
use quote::{quote, ToTokens};
use syn::{spanned::Spanned, *};
use rxml_validation::NcName;
use crate::compound::Compound;
use crate::error_message::{self, ParentRef};
use crate::meta::{AmountConstraint, Flag, NameRef, NamespaceRef, QNameRef, XmlFieldMeta};
use crate::scope::{AsItemsScope, FromEventsScope};
use crate::types::{
as_optional_xml_text_fn, as_xml_iter_fn, as_xml_text_fn, default_fn, extend_fn, from_events_fn,
from_xml_builder_ty, from_xml_text_fn, into_iterator_into_iter_fn, into_iterator_item_ty,
into_iterator_iter_ty, item_iter_ty, option_ty, ref_ty, string_ty, text_codec_decode_fn,
text_codec_encode_fn, ty_from_ident,
};
/// Code slices necessary for declaring and initializing a temporary variable
/// for parsing purposes.
pub(crate) struct FieldTempInit {
/// The type of the temporary variable.
pub(crate) ty: Type,
/// The initializer for the temporary variable.
pub(crate) init: TokenStream,
}
/// Describe how a struct or enum variant's member is parsed from XML data.
///
/// This struct is returned from [`FieldDef::make_builder_part`] and
/// contains code snippets and instructions for
/// [`Compound::make_from_events_statemachine`][`crate::compound::Compound::make_from_events_statemachine`]
/// to parse the field's data from XML.
pub(crate) enum FieldBuilderPart {
/// Parse a field from the item's element's start event.
Init {
/// Expression and type which extracts the field's data from the
/// element's start event.
value: FieldTempInit,
},
/// Parse a field from text events.
Text {
/// Expression and type which initializes a buffer to use during
/// parsing.
value: FieldTempInit,
/// Statement which takes text and accumulates it into the temporary
/// value declared via `value`.
collect: TokenStream,
/// Expression which evaluates to the field's type, consuming the
/// temporary value.
finalize: TokenStream,
},
/// Parse a field from child element events.
Nested {
/// Additional definition items which need to be inserted at module
/// level for the rest of the implementation to work.
extra_defs: TokenStream,
/// Expression and type which initializes a buffer to use during
/// parsing.
value: FieldTempInit,
/// Expression which evaluates to `Result<T, FromEventsError>`,
/// consuming `name: rxml::QName` and `attrs: rxml::AttrMap`.
///
/// `T` must be the type specified in the
/// [`Self::Nested::builder`] field.
matcher: TokenStream,
/// Type implementing `xso::FromEventsBuilder` which parses the child
/// element.
///
/// This type is returned by the expressions in
/// [`matcher`][`Self::Nested::matcher`].
builder: Type,
/// Expression which consumes the value stored in the identifier
/// [`crate::common::FromEventsScope::substate_result`][`FromEventsScope::substate_result`]
/// and somehow collects it into the field declared with
/// [`value`][`Self::Nested::value`].
collect: TokenStream,
/// Expression which consumes the data from the field declared with
/// [`value`][`Self::Nested::value`] and converts it into the field's
/// type.
finalize: TokenStream,
},
}
/// Describe how a struct or enum variant's member is converted to XML data.
///
/// This struct is returned from [`FieldDef::make_iterator_part`] and
/// contains code snippets and instructions for
/// [`Compound::make_into_events_statemachine`][`crate::compound::Compound::make_into_events_statemachine`]
/// to convert the field's data into XML.
pub(crate) enum FieldIteratorPart {
/// The field is emitted as part of StartElement.
Header {
/// An expression which consumes the field's value and returns a
/// `Item`.
generator: TokenStream,
},
/// The field is emitted as text item.
Text {
/// An expression which consumes the field's value and returns a
/// String, which is then emitted as text data.
generator: TokenStream,
},
/// The field is emitted as series of items which form a child element.
Content {
/// Additional definition items which need to be inserted at module
/// level for the rest of the implementation to work.
extra_defs: TokenStream,
/// Expression and type which initializes the nested iterator.
///
/// Note that this is evaluated at construction time of the iterator.
/// Fields of this variant do not get access to their original data,
/// unless they carry it in the contents of this `value`.
value: FieldTempInit,
/// An expression which uses the value (mutably) and evaluates to
/// a Result<Option<Item>, Error>. Once the state returns None, the
/// processing will advance to the next state.
generator: TokenStream,
},
}
/// Definition of what to extract from a child element.
struct ExtractDef {
/// The XML namespace of the child to extract data from.
xml_namespace: NamespaceRef,
/// The XML name of the child to extract data from.
xml_name: NameRef,
/// Compound which contains the arguments of the `extract(..)` meta
/// (except the `from`), transformed into a struct with unnamed
/// fields.
///
/// This is used to generate the parsing/serialisation code, by
/// essentially "declaring" a shim struct, as if it were a real Rust
/// struct, and using the result of the parsing process directly for
/// the field on which the `extract(..)` option was used, instead of
/// putting it into a Rust struct.
parts: Compound,
}
/// Specify how the field is mapped to XML.
enum FieldKind {
/// The field maps to an attribute.
Attribute {
/// The optional XML namespace of the attribute.
xml_namespace: Option<NamespaceRef>,
/// The XML name of the attribute.
xml_name: NameRef,
/// Flag indicating whether the value should be defaulted if the
/// attribute is absent.
default_: Flag,
},
/// The field maps to the character data of the element.
Text {
/// Optional codec to use
codec: Option<Expr>,
},
/// The field maps to a child
Child {
/// Flag indicating whether the value should be defaulted if the
/// child is absent.
default_: Flag,
/// Number of child elements allowed.
amount: AmountConstraint,
/// If set, the child element is not parsed as a field implementing
/// `FromXml` / `AsXml`, but instead its contents are extracted.
extract: Option<ExtractDef>,
},
}
fn default_name(span: Span, name: Option<NameRef>, field_ident: Option<&Ident>) -> Result<NameRef> {
match name {
Some(v) => Ok(v),
None => match field_ident {
None => Err(Error::new(
span,
"name must be explicitly specified with the `name` key on unnamed fields",
)),
Some(field_ident) => match NcName::try_from(field_ident.to_string()) {
Ok(value) => Ok(NameRef::Literal {
span: field_ident.span(),
value,
}),
Err(e) => Err(Error::new(
field_ident.span(),
format!("invalid XML name: {}", e),
)),
},
},
}
}
impl FieldKind {
/// Construct a new field implementation from the meta attributes.
///
/// `field_ident` is, for some field types, used to infer an XML name if
/// it is not specified explicitly.
///
/// `field_ty` is needed for type inferrence on extracted fields.
///
/// `container_namespace` is used in some cases to insert a default
/// namespace.
fn from_meta(
meta: XmlFieldMeta,
field_ident: Option<&Ident>,
field_ty: &Type,
container_namespace: &NamespaceRef,
) -> Result<Self> {
match meta {
XmlFieldMeta::Attribute {
span,
qname: QNameRef { namespace, name },
default_,
type_,
} => {
let xml_name = default_name(span, name, field_ident)?;
// This would've been taken via `XmlFieldMeta::take_type` if
// this field was within an extract where a `type_` is legal
// to have.
if let Some(type_) = type_ {
return Err(Error::new_spanned(
type_,
"specifying `type_` on fields inside structs and enum variants is redundant and not allowed."
));
}
Ok(Self::Attribute {
xml_name,
xml_namespace: namespace,
default_,
})
}
XmlFieldMeta::Text {
span: _,
codec,
type_,
} => {
// This would've been taken via `XmlFieldMeta::take_type` if
// this field was within an extract where a `type_` is legal
// to have.
if let Some(type_) = type_ {
return Err(Error::new_spanned(
type_,
"specifying `type_` on fields inside structs and enum variants is redundant and not allowed."
));
}
Ok(Self::Text { codec })
}
XmlFieldMeta::Child {
span: _,
default_,
amount,
} => {
if let Some(AmountConstraint::Any(ref amount_span)) = amount {
if let Flag::Present(ref flag_span) = default_ {
let mut err = Error::new(
*flag_span,
"`default` has no meaning for child collections",
);
err.combine(Error::new(
*amount_span,
"the field is treated as a collection because of this `n` value",
));
return Err(err);
}
}
Ok(Self::Child {
default_,
amount: amount.unwrap_or(AmountConstraint::FixedSingle(Span::call_site())),
extract: None,
})
}
XmlFieldMeta::Extract {
span,
qname: QNameRef { namespace, name },
amount,
fields,
} => {
let xml_namespace = namespace.unwrap_or_else(|| container_namespace.clone());
let xml_name = default_name(span, name, field_ident)?;
let mut field = {
let mut fields = fields.into_iter();
let Some(field) = fields.next() else {
return Err(Error::new(
span,
"`#[xml(extract(..))]` must contain one `fields(..)` nested meta which contains at least one field meta."
));
};
if let Some(field) = fields.next() {
return Err(Error::new(
field.span(),
"more than one extracted piece of data is currently not supported",
));
}
field
};
let amount = amount.unwrap_or(AmountConstraint::FixedSingle(Span::call_site()));
let field_ty = match field.take_type() {
Some(v) => v,
None => match amount {
// Only allow inferrence for single values: inferrence
// for collections will always be wrong.
AmountConstraint::FixedSingle(_) => field_ty.clone(),
_ => {
return Err(Error::new(
field.span(),
"extracted field must specify a type explicitly when extracting into a collection."
));
}
},
};
let parts = Compound::from_field_defs(
[FieldDef::from_extract(field, 0, &field_ty, &xml_namespace)].into_iter(),
)?;
Ok(Self::Child {
default_: Flag::Absent,
amount,
extract: Some(ExtractDef {
xml_namespace,
xml_name,
parts,
}),
})
}
}
}
}
/// Definition of a single field in a compound.
///
/// See [`Compound`][`crate::compound::Compound`] for more information on
/// compounds in general.
pub(crate) struct FieldDef {
/// The member identifying the field.
member: Member,
/// The type of the field.
ty: Type,
/// The way the field is mapped to XML.
kind: FieldKind,
}
impl FieldDef {
/// Create a new field definition from its declaration.
///
/// The `index` must be the zero-based index of the field even for named
/// fields.
pub(crate) fn from_field(
field: &syn::Field,
index: u32,
container_namespace: &NamespaceRef,
) -> Result<Self> {
let field_span = field.span();
let meta = XmlFieldMeta::parse_from_attributes(&field.attrs, &field_span)?;
let (member, ident) = match field.ident.as_ref() {
Some(v) => (Member::Named(v.clone()), Some(v)),
None => (
Member::Unnamed(Index {
index,
span: field_span,
}),
None,
),
};
let ty = field.ty.clone();
Ok(Self {
kind: FieldKind::from_meta(meta, ident, &ty, container_namespace)?,
member,
ty,
})
}
/// Create a new field definition from its declaration.
///
/// The `index` must be the zero-based index of the field even for named
/// fields.
pub(crate) fn from_extract(
meta: XmlFieldMeta,
index: u32,
ty: &Type,
container_namespace: &NamespaceRef,
) -> Result<Self> {
let span = meta.span();
Ok(Self {
member: Member::Unnamed(Index { index, span }),
ty: ty.clone(),
kind: FieldKind::from_meta(meta, None, ty, container_namespace)?,
})
}
/// Access the [`syn::Member`] identifying this field in the original
/// type.
pub(crate) fn member(&self) -> &Member {
&self.member
}
/// Access the field's type.
pub(crate) fn ty(&self) -> &Type {
&self.ty
}
/// Construct the builder pieces for this field.
///
/// `container_name` must be a reference to the compound's type, so that
/// it can be used for error messages.
pub(crate) fn make_builder_part(
&self,
scope: &FromEventsScope,
container_name: &ParentRef,
) -> Result<FieldBuilderPart> {
match self.kind {
FieldKind::Attribute {
ref xml_name,
ref xml_namespace,
ref default_,
} => {
let FromEventsScope { ref attrs, .. } = scope;
let ty = self.ty.clone();
let missing_msg = error_message::on_missing_attribute(container_name, &self.member);
let xml_namespace = match xml_namespace {
Some(v) => v.to_token_stream(),
None => quote! {
::xso::exports::rxml::Namespace::none()
},
};
let from_xml_text = from_xml_text_fn(ty.clone());
let on_absent = match default_ {
Flag::Absent => quote! {
return ::core::result::Result::Err(::xso::error::Error::Other(#missing_msg).into())
},
Flag::Present(_) => {
let default_ = default_fn(ty.clone());
quote! {
#default_()
}
}
};
Ok(FieldBuilderPart::Init {
value: FieldTempInit {
init: quote! {
match #attrs.remove(#xml_namespace, #xml_name).map(#from_xml_text).transpose()? {
::core::option::Option::Some(v) => v,
::core::option::Option::None => #on_absent,
}
},
ty: self.ty.clone(),
},
})
}
FieldKind::Text { ref codec } => {
let FromEventsScope { ref text, .. } = scope;
let field_access = scope.access_field(&self.member);
let finalize = match codec {
Some(codec) => {
let decode = text_codec_decode_fn(self.ty.clone());
quote! {
#decode(&#codec, #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 {
init: quote! { ::std::string::String::new() },
ty: string_ty(Span::call_site()),
},
collect: quote! {
#field_access.push_str(#text.as_str());
},
finalize,
})
}
FieldKind::Child {
ref default_,
ref amount,
ref extract,
} => {
let FromEventsScope {
ref substate_result,
..
} = scope;
let field_access = scope.access_field(&self.member);
let element_ty = match amount {
AmountConstraint::FixedSingle(_) => self.ty.clone(),
AmountConstraint::Any(_) => into_iterator_item_ty(self.ty.clone()),
};
let (extra_defs, matcher, fetch, builder) = match extract {
Some(ExtractDef {
ref xml_namespace,
ref xml_name,
ref parts,
}) => {
let from_xml_builder_ty_ident =
scope.make_member_type_name(&self.member, "FromXmlBuilder");
let state_ty_ident =
quote::format_ident!("{}State", from_xml_builder_ty_ident,);
let extra_defs = parts.make_from_events_statemachine(
&state_ty_ident,
&container_name.child(self.member.clone()),
"",
)?.with_augmented_init(|init| quote! {
if name.0 == #xml_namespace && name.1 == #xml_name {
#init
} else {
::core::result::Result::Err(::xso::error::FromEventsError::Mismatch { name, attrs })
}
}).compile().render(
&Visibility::Inherited,
&from_xml_builder_ty_ident,
&state_ty_ident,
&Type::Tuple(TypeTuple {
paren_token: token::Paren::default(),
elems: [
element_ty.clone(),
].into_iter().collect(),
})
)?;
let from_xml_builder_ty =
ty_from_ident(from_xml_builder_ty_ident.clone()).into();
let matcher = quote! { #state_ty_ident::new(name, attrs).map(|x| #from_xml_builder_ty_ident(::core::option::Option::Some(x))) };
(
extra_defs,
matcher,
quote! { #substate_result.0 },
from_xml_builder_ty,
)
}
None => {
let from_events = from_events_fn(element_ty.clone());
let from_xml_builder = from_xml_builder_ty(element_ty.clone());
let matcher = quote! { #from_events(name, attrs) };
let builder = from_xml_builder;
(
TokenStream::default(),
matcher,
quote! { #substate_result },
builder,
)
}
};
match amount {
AmountConstraint::FixedSingle(_) => {
let missing_msg =
error_message::on_missing_child(container_name, &self.member);
let duplicate_msg =
error_message::on_duplicate_child(container_name, &self.member);
let on_absent = match default_ {
Flag::Absent => quote! {
return ::core::result::Result::Err(::xso::error::Error::Other(#missing_msg).into())
},
Flag::Present(_) => {
let default_ = default_fn(element_ty.clone());
quote! {
#default_()
}
}
};
Ok(FieldBuilderPart::Nested {
extra_defs,
value: FieldTempInit {
init: quote! { ::std::option::Option::None },
ty: option_ty(self.ty.clone()),
},
matcher: quote! {
match #matcher {
::core::result::Result::Ok(v) => if #field_access.is_some() {
::core::result::Result::Err(::xso::error::FromEventsError::Invalid(::xso::error::Error::Other(#duplicate_msg)))
} else {
::core::result::Result::Ok(v)
},
::core::result::Result::Err(e) => ::core::result::Result::Err(e),
}
},
builder,
collect: quote! {
#field_access = ::std::option::Option::Some(#fetch);
},
finalize: quote! {
match #field_access {
::std::option::Option::Some(value) => value,
::std::option::Option::None => #on_absent,
}
},
})
}
AmountConstraint::Any(_) => {
let ty_extend = extend_fn(self.ty.clone(), element_ty.clone());
let ty_default = default_fn(self.ty.clone());
Ok(FieldBuilderPart::Nested {
extra_defs,
value: FieldTempInit {
init: quote! { #ty_default() },
ty: self.ty.clone(),
},
matcher,
builder,
collect: quote! {
#ty_extend(&mut #field_access, [#fetch]);
},
finalize: quote! { #field_access },
})
}
}
}
}
}
/// Construct the iterator pieces for this field.
///
/// `bound_name` must be the name to which the field's value is bound in
/// the iterator code.
pub(crate) fn make_iterator_part(
&self,
scope: &AsItemsScope,
container_name: &ParentRef,
bound_name: &Ident,
) -> Result<FieldIteratorPart> {
match self.kind {
FieldKind::Attribute {
ref xml_name,
ref xml_namespace,
..
} => {
let xml_namespace = match xml_namespace {
Some(v) => quote! { ::xso::exports::rxml::Namespace::from(#v) },
None => quote! {
::xso::exports::rxml::Namespace::NONE
},
};
let as_optional_xml_text = as_optional_xml_text_fn(self.ty.clone());
Ok(FieldIteratorPart::Header {
generator: quote! {
#as_optional_xml_text(#bound_name)?.map(|#bound_name| ::xso::Item::Attribute(
#xml_namespace,
::std::borrow::Cow::Borrowed(#xml_name),
#bound_name,
));
},
})
}
FieldKind::Text { ref codec } => {
let generator = match codec {
Some(codec) => {
let encode = text_codec_encode_fn(self.ty.clone());
quote! { #encode(&#codec, #bound_name)? }
}
None => {
let as_xml_text = as_xml_text_fn(self.ty.clone());
quote! { ::core::option::Option::Some(#as_xml_text(#bound_name)?) }
}
};
Ok(FieldIteratorPart::Text { generator })
}
FieldKind::Child {
default_: _,
ref amount,
ref extract,
} => {
let AsItemsScope { ref lifetime, .. } = scope;
let item_ty = match amount {
AmountConstraint::FixedSingle(_) => self.ty.clone(),
AmountConstraint::Any(_) => {
// This should give us the type of element stored in the
// collection.
into_iterator_item_ty(self.ty.clone())
}
};
let (extra_defs, fetch, as_xml_iter, iter_ty) = match extract {
Some(ExtractDef {
ref xml_namespace,
ref xml_name,
ref parts,
}) => {
let item_iter_ty_ident =
scope.make_member_type_name(&self.member, "AsXmlIterator");
let state_ty_ident = quote::format_ident!("{}State", item_iter_ty_ident,);
let mut item_iter_ty = ty_from_ident(item_iter_ty_ident.clone());
item_iter_ty.path.segments[0].arguments =
PathArguments::AngleBracketed(AngleBracketedGenericArguments {
colon2_token: None,
lt_token: token::Lt::default(),
args: [GenericArgument::Lifetime(lifetime.clone())]
.into_iter()
.collect(),
gt_token: token::Gt::default(),
});
let item_iter_ty = item_iter_ty.into();
let extra_defs = parts
.make_as_item_iter_statemachine(
&container_name.child(self.member.clone()),
&state_ty_ident,
"",
lifetime,
)?
.with_augmented_init(|init| {
quote! {
let name = (
::xso::exports::rxml::Namespace::from(#xml_namespace),
::std::borrow::Cow::Borrowed(#xml_name),
);
#init
}
})
.compile()
.render(
&Visibility::Inherited,
&Type::Tuple(TypeTuple {
paren_token: token::Paren::default(),
elems: [ref_ty(item_ty.clone(), lifetime.clone())]
.into_iter()
.collect(),
}),
&state_ty_ident,
lifetime,
&item_iter_ty,
)?;
(
extra_defs,
quote! { (&#bound_name,) },
quote! { #item_iter_ty_ident::new },
item_iter_ty,
)
}
None => {
let as_xml_iter = as_xml_iter_fn(item_ty.clone());
let item_iter = item_iter_ty(item_ty.clone(), lifetime.clone());
(
TokenStream::default(),
quote! { #bound_name },
quote! { #as_xml_iter },
item_iter,
)
}
};
match amount {
AmountConstraint::FixedSingle(_) => Ok(FieldIteratorPart::Content {
extra_defs,
value: FieldTempInit {
init: quote! {
#as_xml_iter(#fetch)?
},
ty: iter_ty,
},
generator: quote! {
#bound_name.next().transpose()
},
}),
AmountConstraint::Any(_) => {
// This is the collection type we actually work
// with -- as_xml_iter uses references after all.
let ty = ref_ty(self.ty.clone(), lifetime.clone());
// But the iterator for iterating over the elements
// inside the collection must use the ref type.
let element_iter = into_iterator_iter_ty(ty.clone());
// And likewise the into_iter impl.
let into_iter = into_iterator_into_iter_fn(ty.clone());
let state_ty = Type::Tuple(TypeTuple {
paren_token: token::Paren::default(),
elems: [element_iter, option_ty(iter_ty)].into_iter().collect(),
});
Ok(FieldIteratorPart::Content {
extra_defs,
value: FieldTempInit {
init: quote! {
(#into_iter(#bound_name), ::core::option::Option::None)
},
ty: state_ty,
},
generator: quote! {
loop {
if let ::core::option::Option::Some(current) = #bound_name.1.as_mut() {
if let ::core::option::Option::Some(item) = current.next() {
break ::core::option::Option::Some(item).transpose();
}
}
if let ::core::option::Option::Some(item) = #bound_name.0.next() {
#bound_name.1 = ::core::option::Option::Some(#as_xml_iter({ let #bound_name = item; #fetch })?)
} else {
break ::core::result::Result::Ok(::core::option::Option::None)
}
}
},
})
}
}
}
}
}
/// Return true if this field's parsing consumes text data.
pub(crate) fn is_text_field(&self) -> bool {
matches!(self.kind, FieldKind::Text { .. })
}
}