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Added implementation of #[field(flatten)]. #2225

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Added implementation of #[field(flatten)]. #2225

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9 changes: 9 additions & 0 deletions core/codegen/src/derive/form_field.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -19,6 +19,7 @@ pub struct FieldAttr {
pub validate: Option<SpanWrapped<syn::Expr>>,
pub default: Option<syn::Expr>,
pub default_with: Option<syn::Expr>,
pub flatten: Option<bool>,
}

impl FieldAttr {
Expand All @@ -33,6 +34,7 @@ pub(crate) trait FieldExt {
fn first_field_name(&self) -> Result<Option<FieldName>>;
fn stripped_ty(&self) -> syn::Type;
fn name_buf_opt(&self) -> Result<TokenStream>;
fn is_flattened(&self) -> Result<bool>;
}

#[derive(FromMeta)]
Expand Down Expand Up @@ -201,6 +203,13 @@ impl FieldExt for Field<'_> {
.map(|name| quote_spanned!(span => Some(#_form::NameBuf::from((__c.__parent, #name)))))
.unwrap_or_else(|| quote_spanned!(span => None::<#_form::NameBuf>)))
}

fn is_flattened(&self) -> Result<bool> {
Ok(FieldAttr::from_attrs(FieldAttr::NAME, &self.attrs)?
.into_iter()
.filter_map(|attr| attr.flatten)
.last().unwrap_or(false))
}
}

struct RecordMemberAccesses(Vec<syn::Member>);
Expand Down
39 changes: 29 additions & 10 deletions core/codegen/src/derive/from_form.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -11,37 +11,56 @@ type WherePredicates = syn::punctuated::Punctuated<syn::WherePredicate, syn::Tok

// F: fn(field_ty: Ty, field_context: Expr)
fn fields_map<F>(fields: Fields<'_>, map_f: F) -> Result<TokenStream>
where F: Fn(&syn::Type, &syn::Expr) -> TokenStream
where F: Fn(&syn::Type, &syn::Expr, &syn::Expr) -> TokenStream
{
let mut matchers = vec![];
let mut flattened_field = None;
for field in fields.iter() {
let (ident, ty) = (field.context_ident(), field.stripped_ty());
let field_context: syn::Expr = syn::parse2(quote_spanned!(ty.span() => {
let __o = __c.__opts;
__c.#ident.get_or_insert_with(|| <#ty as #_form::FromForm<'r>>::init(__o))
})).expect("form context expression");

let push = map_f(&ty, &field_context);
let push = |field: &syn::Expr| map_f(&ty, &field_context, field);
if fields.are_unnamed() {
// If we have unnamed fields, then we have exactly one by virtue of
// the earlier validation. Push directly to it and return.
let push = push(&syn::parse2(quote!(__f.shift())).expect("field value expression"));
return Ok(quote_spanned!(ident.span() =>
__c.__parent = __f.name.parent();
#push
));
}

matchers.extend(field.field_names()?.into_iter().map(|f| match f {
Cased(name) => quote!(#name => { #push }),
Uncased(name) => quote!(__n if __n.as_uncased() == #name => { #push }),
}));
let is_flattened = field.is_flattened()?;

if is_flattened {
let push = push(&syn::parse2(quote!(__f)).expect("field value expression"));
if let Some(flattened_field) = flattened_field {
drop(flattened_field);
todo!("Emit an error.");
} else {
flattened_field = Some(push);
}
} else {
let push = push(&syn::parse2(quote!(__f.shift())).expect("field value expression"));
matchers.extend(field.field_names()?.into_iter().map(|f| match f {
Cased(name) => quote!(#name => { #push }),
Uncased(name) => quote!(__n if __n.as_uncased() == #name => { #push }),
}));
}
}

// TODO: check in options that they aren't strict or pass to flattened fields strict = false.

let flattened_field = flattened_field.iter();
Ok(quote! {
__c.__parent = __f.name.parent();

match __f.name.key_lossy().as_str() {
#(#matchers,)*
#(_ => { #flattened_field },)*
__k if __k == "_method" || !__c.__opts.strict => { /* ok */ },
_ => __c.__errors.push(__f.unexpected()),
}
Expand Down Expand Up @@ -181,8 +200,8 @@ pub fn derive_from_form(input: proc_macro::TokenStream) -> TokenStream {
#output
}
})
.try_fields_map(|_, f| fields_map(f, |ty, ctxt| quote_spanned!(ty.span() => {
<#ty as #_form::FromForm<'r>>::push_value(#ctxt, __f.shift());
.try_fields_map(|_, f| fields_map(f, |ty, ctxt, field| quote_spanned!(ty.span() => {
<#ty as #_form::FromForm<'r>>::push_value(#ctxt, #field);
})))
)
.inner_mapper(MapperBuild::new()
Expand All @@ -201,8 +220,8 @@ pub fn derive_from_form(input: proc_macro::TokenStream) -> TokenStream {
})
// Without the `let _fut`, we get a wild lifetime error. It don't
// make no sense, Rust async/await: it don't make no sense.
.try_fields_map(|_, f| fields_map(f, |ty, ctxt| quote_spanned!(ty.span() => {
let _fut = <#ty as #_form::FromForm<'r>>::push_data(#ctxt, __f.shift());
.try_fields_map(|_, f| fields_map(f, |ty, ctxt, field| quote_spanned!(ty.span() => {
let _fut = <#ty as #_form::FromForm<'r>>::push_data(#ctxt, #field);
_fut.await;
})))
)
Expand Down