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der/derive: support for skipped field #1008

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14 changes: 14 additions & 0 deletions der/derive/src/attributes.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -79,6 +79,9 @@ pub(crate) struct FieldAttrs {

/// Is the inner type constructed?
pub constructed: bool,

/// Is the type skipped?
pub skipped: Option<Path>,
}

impl FieldAttrs {
Expand All @@ -98,6 +101,7 @@ impl FieldAttrs {
let mut optional = None;
let mut tag_mode = None;
let mut constructed = None;
let mut skipped = None;

let mut parsed_attrs = Vec::new();
AttrNameValue::from_attributes(attrs, &mut parsed_attrs);
Expand Down Expand Up @@ -154,6 +158,15 @@ impl FieldAttrs {
}

constructed = Some(ty);
// `skipped` attribute
} else if attr.parse_value::<String>("skipped").is_some() {
if skipped.is_some() {
abort!(attr.name, "duplicate ASN.1 `skipped` attribute");
}

skipped = Some(attr.value.parse().unwrap_or_else(|e| {
abort!(attr.value, "error parsing ASN.1 `skipped` attribute: {}", e)
}));
} else {
abort!(
attr.name,
Expand All @@ -171,6 +184,7 @@ impl FieldAttrs {
optional: optional.unwrap_or_default(),
tag_mode: tag_mode.unwrap_or(type_attrs.tag_mode),
constructed: constructed.unwrap_or_default(),
skipped,
}
}

Expand Down
28 changes: 21 additions & 7 deletions der/derive/src/sequence.rs
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Expand Up @@ -8,7 +8,7 @@ use field::SequenceField;
use proc_macro2::TokenStream;
use proc_macro_error::abort;
use quote::quote;
use syn::{DeriveInput, Ident, Lifetime};
use syn::{DeriveInput, Ident, Lifetime, TypeParam};

/// Derive the `Sequence` trait for a struct
pub(crate) struct DeriveSequence {
Expand All @@ -18,6 +18,9 @@ pub(crate) struct DeriveSequence {
/// Lifetime of the struct.
lifetime: Option<Lifetime>,

/// Type param of the struct.
type_param: Option<TypeParam>,

/// Fields of the struct.
fields: Vec<SequenceField>,
}
Expand All @@ -40,6 +43,8 @@ impl DeriveSequence {
.next()
.map(|lt| lt.lifetime.clone());

let type_param = input.generics.type_params().next().cloned();

let type_attrs = TypeAttrs::parse(&input.attrs);

let fields = data
Expand All @@ -51,6 +56,7 @@ impl DeriveSequence {
Self {
ident: input.ident,
lifetime,
type_param,
fields,
}
}
Expand All @@ -72,6 +78,13 @@ impl DeriveSequence {
.map(|_| lifetime.clone())
.unwrap_or_default();

let type_params = self.type_param.as_ref().map(|t| {
let mut t = t.clone();
t.default = None;
t
});
let type_params_names = self.type_param.as_ref().map(|t| t.ident.clone());

let mut decode_body = Vec::new();
let mut decode_result = Vec::new();
let mut encoded_lengths = Vec::new();
Expand All @@ -81,13 +94,14 @@ impl DeriveSequence {
decode_body.push(field.to_decode_tokens());
decode_result.push(&field.ident);

let field = field.to_encode_tokens();
encoded_lengths.push(quote!(#field.encoded_len()?));
encode_fields.push(quote!(#field.encode(writer)?;));
if let Some(field) = field.to_encode_tokens() {
encoded_lengths.push(quote!(#field.encoded_len()?));
encode_fields.push(quote!(#field.encode(writer)?;));
}
}

quote! {
impl<#lifetime> ::der::DecodeValue<#lifetime> for #ident<#lt_params> {
impl<#lifetime, #type_params> ::der::DecodeValue<#lifetime> for #ident<#lt_params #type_params_names> {
fn decode_value<R: ::der::Reader<#lifetime>>(
reader: &mut R,
header: ::der::Header,
Expand All @@ -104,7 +118,7 @@ impl DeriveSequence {
}
}

impl<#lifetime> ::der::EncodeValue for #ident<#lt_params> {
impl<#lifetime, #type_params> ::der::EncodeValue for #ident<#lt_params #type_params_names> {
fn value_len(&self) -> ::der::Result<::der::Length> {
use ::der::Encode as _;

Expand All @@ -122,7 +136,7 @@ impl DeriveSequence {
}
}

impl<#lifetime> ::der::Sequence<#lifetime> for #ident<#lt_params> {}
impl<#lifetime, #type_params> ::der::Sequence<#lifetime> for #ident<#lt_params #type_params_names> {}
}
}
}
Expand Down
71 changes: 66 additions & 5 deletions der/derive/src/sequence/field.rs
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Expand Up @@ -72,11 +72,22 @@ impl SequenceField {
}
}

if let Some(default) = &self.attrs.skipped {
let ident = &self.ident;
return quote! {
let #ident = #default();
};
}

lowerer.into_tokens(&self.ident)
}

/// Derive code for encoding a field of a sequence.
pub(super) fn to_encode_tokens(&self) -> TokenStream {
pub(super) fn to_encode_tokens(&self) -> Option<TokenStream> {
if self.attrs.skipped.is_some() {
return None;
}

let mut lowerer = LowerFieldEncoder::new(&self.ident);
let attrs = &self.attrs;

Expand All @@ -101,7 +112,7 @@ impl SequenceField {
lowerer.apply_default(&self.ident, default);
}

lowerer.into_tokens()
Some(lowerer.into_tokens())
}
}

Expand Down Expand Up @@ -241,7 +252,7 @@ mod tests {
use crate::{FieldAttrs, TagMode, TagNumber};
use proc_macro2::Span;
use quote::quote;
use syn::{punctuated::Punctuated, Ident, Path, PathSegment, Type, TypePath};
use syn::{punctuated::Punctuated, Ident, Path, PathArguments, PathSegment, Type, TypePath};

/// Create a [`Type::Path`].
pub fn type_path(ident: Ident) -> Type {
Expand Down Expand Up @@ -273,6 +284,7 @@ mod tests {
optional: false,
tag_mode: TagMode::Explicit,
constructed: false,
skipped: None,
};

let field_type = Ident::new("String", span);
Expand All @@ -292,7 +304,7 @@ mod tests {
);

assert_eq!(
field.to_encode_tokens().to_string(),
field.to_encode_tokens().unwrap().to_string(),
quote! {
self.example_field
}
Expand All @@ -313,6 +325,7 @@ mod tests {
optional: false,
tag_mode: TagMode::Implicit,
constructed: false,
skipped: None,
};

let field_type = Ident::new("String", span);
Expand Down Expand Up @@ -343,7 +356,7 @@ mod tests {
);

assert_eq!(
field.to_encode_tokens().to_string(),
field.to_encode_tokens().unwrap().to_string(),
quote! {
::der::asn1::ContextSpecificRef {
tag_number: ::der::TagNumber::N0,
Expand All @@ -354,4 +367,52 @@ mod tests {
.to_string()
);
}

#[test]
fn skipped() {
let span = Span::call_site();
let ident = Ident::new("skipped", span);

let mut segments = Punctuated::new();
segments.push(PathSegment {
ident: Ident::new("Default", span),
arguments: PathArguments::None,
});
segments.push(PathSegment {
ident: Ident::new("default", span),
arguments: PathArguments::None,
});

let attrs = FieldAttrs {
asn1_type: None,
context_specific: Some(TagNumber(0)),
default: None,
extensible: false,
optional: false,
tag_mode: TagMode::Implicit,
constructed: false,
skipped: Some(Path {
leading_colon: None,
segments,
}),
};

let field_type = Ident::new("String", span);

let field = SequenceField {
ident,
attrs,
field_type: type_path(field_type),
};

assert_eq!(
field.to_decode_tokens().to_string(),
quote! {
let skipped = Default::default();
}
.to_string()
);

assert!(field.to_encode_tokens().is_none());
}
}
4 changes: 4 additions & 0 deletions der/derive/src/value_ord.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -171,6 +171,10 @@ impl ValueField {

/// Lower to [`TokenStream`].
fn to_tokens(&self) -> TokenStream {
if self.attrs.skipped.is_some() {
return TokenStream::default();
}

let ident = &self.ident;

if self.is_enum {
Expand Down