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use crate::internals::ast::{Container, Data, Field, Style};
use crate::internals::attr::{Default, Identifier, TagType};
use crate::internals::{ungroup, Ctxt, Derive};
use syn::{Member, Type};
// Cross-cutting checks that require looking at more than a single attrs object.
// Simpler checks should happen when parsing and building the attrs.
pub fn check(cx: &Ctxt, cont: &mut Container, derive: Derive) {
check_default_on_tuple(cx, cont);
check_remote_generic(cx, cont);
check_getter(cx, cont);
check_flatten(cx, cont);
check_identifier(cx, cont);
check_variant_skip_attrs(cx, cont);
check_internal_tag_field_name_conflict(cx, cont);
check_adjacent_tag_conflict(cx, cont);
check_transparent(cx, cont, derive);
check_from_and_try_from(cx, cont);
}
// If some field of a tuple struct is marked #[serde(default)] then all fields
// after it must also be marked with that attribute, or the struct must have a
// container-level serde(default) attribute. A field's default value is only
// used for tuple fields if the sequence is exhausted at that point; that means
// all subsequent fields will fail to deserialize if they don't have their own
// default.
fn check_default_on_tuple(cx: &Ctxt, cont: &Container) {
if let Default::None = cont.attrs.default() {
if let Data::Struct(Style::Tuple, fields) = &cont.data {
let mut first_default_index = None;
for (i, field) in fields.iter().enumerate() {
// Skipped fields automatically get the #[serde(default)]
// attribute. We are interested only on non-skipped fields here.
if field.attrs.skip_deserializing() {
continue;
}
if let Default::None = field.attrs.default() {
if let Some(first) = first_default_index {
cx.error_spanned_by(
field.ty,
format!("field must have #[serde(default)] because previous field {} has #[serde(default)]", first),
);
}
continue;
}
if first_default_index.is_none() {
first_default_index = Some(i);
}
}
}
}
}
// Remote derive definition type must have either all of the generics of the
// remote type:
//
// #[serde(remote = "Generic")]
// struct Generic<T> {…}
//
// or none of them, i.e. defining impls for one concrete instantiation of the
// remote type only:
//
// #[serde(remote = "Generic<T>")]
// struct ConcreteDef {…}
//
fn check_remote_generic(cx: &Ctxt, cont: &Container) {
if let Some(remote) = cont.attrs.remote() {
let local_has_generic = !cont.generics.params.is_empty();
let remote_has_generic = !remote.segments.last().unwrap().arguments.is_none();
if local_has_generic && remote_has_generic {
cx.error_spanned_by(remote, "remove generic parameters from this path");
}
}
}
// Getters are only allowed inside structs (not enums) with the `remote`
// attribute.
fn check_getter(cx: &Ctxt, cont: &Container) {
match cont.data {
Data::Enum(_) => {
if cont.data.has_getter() {
cx.error_spanned_by(
cont.original,
"#[serde(getter = \"...\")] is not allowed in an enum",
);
}
}
Data::Struct(_, _) => {
if cont.data.has_getter() && cont.attrs.remote().is_none() {
cx.error_spanned_by(
cont.original,
"#[serde(getter = \"...\")] can only be used in structs that have #[serde(remote = \"...\")]",
);
}
}
}
}
// Flattening has some restrictions we can test.
fn check_flatten(cx: &Ctxt, cont: &Container) {
match &cont.data {
Data::Enum(variants) => {
for variant in variants {
for field in &variant.fields {
check_flatten_field(cx, variant.style, field);
}
}
}
Data::Struct(style, fields) => {
for field in fields {
check_flatten_field(cx, *style, field);
}
}
}
}
fn check_flatten_field(cx: &Ctxt, style: Style, field: &Field) {
if !field.attrs.flatten() {
return;
}
match style {
Style::Tuple => {
cx.error_spanned_by(
field.original,
"#[serde(flatten)] cannot be used on tuple structs",
);
}
Style::Newtype => {
cx.error_spanned_by(
field.original,
"#[serde(flatten)] cannot be used on newtype structs",
);
}
_ => {}
}
}
// The `other` attribute must be used at most once and it must be the last
// variant of an enum.
//
// Inside a `variant_identifier` all variants must be unit variants. Inside a
// `field_identifier` all but possibly one variant must be unit variants. The
// last variant may be a newtype variant which is an implicit "other" case.
fn check_identifier(cx: &Ctxt, cont: &Container) {
let variants = match &cont.data {
Data::Enum(variants) => variants,
Data::Struct(_, _) => return,
};
for (i, variant) in variants.iter().enumerate() {
match (
variant.style,
cont.attrs.identifier(),
variant.attrs.other(),
cont.attrs.tag(),
) {
// The `other` attribute may not be used in a variant_identifier.
(_, Identifier::Variant, true, _) => {
cx.error_spanned_by(
variant.original,
"#[serde(other)] may not be used on a variant identifier",
);
}
// Variant with `other` attribute cannot appear in untagged enum
(_, Identifier::No, true, &TagType::None) => {
cx.error_spanned_by(
variant.original,
"#[serde(other)] cannot appear on untagged enum",
);
}
// Variant with `other` attribute must be the last one.
(Style::Unit, Identifier::Field, true, _) | (Style::Unit, Identifier::No, true, _) => {
if i < variants.len() - 1 {
cx.error_spanned_by(
variant.original,
"#[serde(other)] must be on the last variant",
);
}
}
// Variant with `other` attribute must be a unit variant.
(_, Identifier::Field, true, _) | (_, Identifier::No, true, _) => {
cx.error_spanned_by(
variant.original,
"#[serde(other)] must be on a unit variant",
);
}
// Any sort of variant is allowed if this is not an identifier.
(_, Identifier::No, false, _) => {}
// Unit variant without `other` attribute is always fine.
(Style::Unit, _, false, _) => {}
// The last field is allowed to be a newtype catch-all.
(Style::Newtype, Identifier::Field, false, _) => {
if i < variants.len() - 1 {
cx.error_spanned_by(
variant.original,
format!("`{}` must be the last variant", variant.ident),
);
}
}
(_, Identifier::Field, false, _) => {
cx.error_spanned_by(
variant.original,
"#[serde(field_identifier)] may only contain unit variants",
);
}
(_, Identifier::Variant, false, _) => {
cx.error_spanned_by(
variant.original,
"#[serde(variant_identifier)] may only contain unit variants",
);
}
}
}
}
// Skip-(de)serializing attributes are not allowed on variants marked
// (de)serialize_with.
fn check_variant_skip_attrs(cx: &Ctxt, cont: &Container) {
let variants = match &cont.data {
Data::Enum(variants) => variants,
Data::Struct(_, _) => return,
};
for variant in variants {
if variant.attrs.serialize_with().is_some() {
if variant.attrs.skip_serializing() {
cx.error_spanned_by(
variant.original,
format!(
"variant `{}` cannot have both #[serde(serialize_with)] and #[serde(skip_serializing)]",
variant.ident
),
);
}
for field in &variant.fields {
let member = member_message(&field.member);
if field.attrs.skip_serializing() {
cx.error_spanned_by(
variant.original,
format!(
"variant `{}` cannot have both #[serde(serialize_with)] and a field {} marked with #[serde(skip_serializing)]",
variant.ident, member
),
);
}
if field.attrs.skip_serializing_if().is_some() {
cx.error_spanned_by(
variant.original,
format!(
"variant `{}` cannot have both #[serde(serialize_with)] and a field {} marked with #[serde(skip_serializing_if)]",
variant.ident, member
),
);
}
}
}
if variant.attrs.deserialize_with().is_some() {
if variant.attrs.skip_deserializing() {
cx.error_spanned_by(
variant.original,
format!(
"variant `{}` cannot have both #[serde(deserialize_with)] and #[serde(skip_deserializing)]",
variant.ident
),
);
}
for field in &variant.fields {
if field.attrs.skip_deserializing() {
let member = member_message(&field.member);
cx.error_spanned_by(
variant.original,
format!(
"variant `{}` cannot have both #[serde(deserialize_with)] and a field {} marked with #[serde(skip_deserializing)]",
variant.ident, member
),
);
}
}
}
}
}
// The tag of an internally-tagged struct variant must not be the same as either
// one of its fields, as this would result in duplicate keys in the serialized
// output and/or ambiguity in the to-be-deserialized input.
fn check_internal_tag_field_name_conflict(cx: &Ctxt, cont: &Container) {
let variants = match &cont.data {
Data::Enum(variants) => variants,
Data::Struct(_, _) => return,
};
let tag = match cont.attrs.tag() {
TagType::Internal { tag } => tag.as_str(),
TagType::External | TagType::Adjacent { .. } | TagType::None => return,
};
let diagnose_conflict = || {
cx.error_spanned_by(
cont.original,
format!("variant field name `{}` conflicts with internal tag", tag),
);
};
for variant in variants {
match variant.style {
Style::Struct => {
if variant.attrs.untagged() {
continue;
}
for field in &variant.fields {
let check_ser =
!(field.attrs.skip_serializing() || variant.attrs.skip_serializing());
let check_de =
!(field.attrs.skip_deserializing() || variant.attrs.skip_deserializing());
let name = field.attrs.name();
let ser_name = name.serialize_name();
if check_ser && ser_name == tag {
diagnose_conflict();
return;
}
for de_name in field.attrs.aliases() {
if check_de && de_name == tag {
diagnose_conflict();
return;
}
}
}
}
Style::Unit | Style::Newtype | Style::Tuple => {}
}
}
}
// In the case of adjacently-tagged enums, the type and the contents tag must
// differ, for the same reason.
fn check_adjacent_tag_conflict(cx: &Ctxt, cont: &Container) {
let (type_tag, content_tag) = match cont.attrs.tag() {
TagType::Adjacent { tag, content } => (tag, content),
TagType::Internal { .. } | TagType::External | TagType::None => return,
};
if type_tag == content_tag {
cx.error_spanned_by(
cont.original,
format!(
"enum tags `{}` for type and content conflict with each other",
type_tag
),
);
}
}
// Enums and unit structs cannot be transparent.
fn check_transparent(cx: &Ctxt, cont: &mut Container, derive: Derive) {
if !cont.attrs.transparent() {
return;
}
if cont.attrs.type_from().is_some() {
cx.error_spanned_by(
cont.original,
"#[serde(transparent)] is not allowed with #[serde(from = \"...\")]",
);
}
if cont.attrs.type_try_from().is_some() {
cx.error_spanned_by(
cont.original,
"#[serde(transparent)] is not allowed with #[serde(try_from = \"...\")]",
);
}
if cont.attrs.type_into().is_some() {
cx.error_spanned_by(
cont.original,
"#[serde(transparent)] is not allowed with #[serde(into = \"...\")]",
);
}
let fields = match &mut cont.data {
Data::Enum(_) => {
cx.error_spanned_by(
cont.original,
"#[serde(transparent)] is not allowed on an enum",
);
return;
}
Data::Struct(Style::Unit, _) => {
cx.error_spanned_by(
cont.original,
"#[serde(transparent)] is not allowed on a unit struct",
);
return;
}
Data::Struct(_, fields) => fields,
};
let mut transparent_field = None;
for field in fields {
if allow_transparent(field, derive) {
if transparent_field.is_some() {
cx.error_spanned_by(
cont.original,
"#[serde(transparent)] requires struct to have at most one transparent field",
);
return;
}
transparent_field = Some(field);
}
}
match transparent_field {
Some(transparent_field) => transparent_field.attrs.mark_transparent(),
None => match derive {
Derive::Serialize => {
cx.error_spanned_by(
cont.original,
"#[serde(transparent)] requires at least one field that is not skipped",
);
}
Derive::Deserialize => {
cx.error_spanned_by(
cont.original,
"#[serde(transparent)] requires at least one field that is neither skipped nor has a default",
);
}
},
}
}
fn member_message(member: &Member) -> String {
match member {
Member::Named(ident) => format!("`{}`", ident),
Member::Unnamed(i) => format!("#{}", i.index),
}
}
fn allow_transparent(field: &Field, derive: Derive) -> bool {
if let Type::Path(ty) = ungroup(field.ty) {
if let Some(seg) = ty.path.segments.last() {
if seg.ident == "PhantomData" {
return false;
}
}
}
match derive {
Derive::Serialize => !field.attrs.skip_serializing(),
Derive::Deserialize => !field.attrs.skip_deserializing() && field.attrs.default().is_none(),
}
}
fn check_from_and_try_from(cx: &Ctxt, cont: &mut Container) {
if cont.attrs.type_from().is_some() && cont.attrs.type_try_from().is_some() {
cx.error_spanned_by(
cont.original,
"#[serde(from = \"...\")] and #[serde(try_from = \"...\")] conflict with each other",
);
}
}