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Fixed derive impl on an empty enum (#462)
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* Fixed derive impl on an empty enum

* Added DecodeError::EmptyEnum in case a user tries to decode an empty enum
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@VictorKoenders
VictorKoenders committed Jan 8, 2022
1 parent db398ec commit 53acac9
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Showing 3 changed files with 131 additions and 90 deletions.
197 changes: 107 additions & 90 deletions derive/src/derive_enum.rs
View file
Expand Up @@ -35,6 +35,9 @@ impl DeriveEnum {
fn_body.ident_str("match");
fn_body.ident_str("self");
fn_body.group(Delimiter::Brace, |match_body| {
if self.variants.is_empty() {
self.encode_empty_enum_case(match_body)?;
}
for (variant_index, variant) in self.iter_fields() {
// Self::Variant
match_body.ident_str("Self");
Expand Down Expand Up @@ -101,18 +104,24 @@ impl DeriveEnum {
?;
}
}
body.push_parsed("Ok(())")?;
Ok(())
})?;
match_body.punct(',');
}
Ok(())
})?;
fn_body.push_parsed("Ok(())")?;
Ok(())
})?;
Ok(())
}

/// If we're encoding an empty enum, we need to add an empty case in the form of:
/// `_ => core::unreachable!(),`
fn encode_empty_enum_case(&self, builder: &mut StreamBuilder) -> Result {
builder.push_parsed("_ => core::unreachable!()").map(|_| ())
}

/// Build the catch-all case for an int-to-enum decode implementation
fn invalid_variant_case(&self, enum_name: &str, result: &mut StreamBuilder) -> Result {
// we'll be generating:
Expand Down Expand Up @@ -195,57 +204,61 @@ impl DeriveEnum {
.with_arg("mut decoder", "D")
.with_return_type("core::result::Result<Self, bincode::error::DecodeError>")
.body(|fn_builder| {
fn_builder
.push_parsed(
"let variant_index = <u32 as bincode::Decode>::decode(&mut decoder)?;",
)?;
fn_builder.push_parsed("match variant_index")?;
fn_builder.group(Delimiter::Brace, |variant_case| {
for (mut variant_index, variant) in self.iter_fields() {
// idx => Ok(..)
if variant_index.len() > 1 {
variant_case.push_parsed("x if x == ")?;
variant_case.extend(variant_index);
} else {
variant_case.push(variant_index.remove(0));
}
variant_case.puncts("=>");
variant_case.ident_str("Ok");
variant_case.group(Delimiter::Parenthesis, |variant_case_body| {
// Self::Variant { }
// Self::Variant { 0: ..., 1: ... 2: ... },
// Self::Variant { a: ..., b: ... c: ... },
variant_case_body.ident_str("Self");
variant_case_body.puncts("::");
variant_case_body.ident(variant.name.clone());
if self.variants.is_empty() {
fn_builder.push_parsed("core::result::Result::Err(bincode::error::DecodeError::EmptyEnum { type_name: core::any::type_name::<Self>() })")?;
} else {
fn_builder
.push_parsed(
"let variant_index = <u32 as bincode::Decode>::decode(&mut decoder)?;",
)?;
fn_builder.push_parsed("match variant_index")?;
fn_builder.group(Delimiter::Brace, |variant_case| {
for (mut variant_index, variant) in self.iter_fields() {
// idx => Ok(..)
if variant_index.len() > 1 {
variant_case.push_parsed("x if x == ")?;
variant_case.extend(variant_index);
} else {
variant_case.push(variant_index.remove(0));
}
variant_case.puncts("=>");
variant_case.ident_str("Ok");
variant_case.group(Delimiter::Parenthesis, |variant_case_body| {
// Self::Variant { }
// Self::Variant { 0: ..., 1: ... 2: ... },
// Self::Variant { a: ..., b: ... c: ... },
variant_case_body.ident_str("Self");
variant_case_body.puncts("::");
variant_case_body.ident(variant.name.clone());

variant_case_body.group(Delimiter::Brace, |variant_body| {
let is_tuple = matches!(variant.fields, Fields::Tuple(_));
for (idx, field) in variant.fields.names().into_iter().enumerate() {
if is_tuple {
variant_body.lit_usize(idx);
} else {
variant_body.ident(field.unwrap_ident().clone());
variant_case_body.group(Delimiter::Brace, |variant_body| {
let is_tuple = matches!(variant.fields, Fields::Tuple(_));
for (idx, field) in variant.fields.names().into_iter().enumerate() {
if is_tuple {
variant_body.lit_usize(idx);
} else {
variant_body.ident(field.unwrap_ident().clone());
}
variant_body.punct(':');
if field.attributes().has_attribute(FieldAttribute::WithSerde)? {
variant_body
.push_parsed("<bincode::serde::Compat<_> as bincode::Decode>::decode(&mut decoder)?.0,")?;
} else {
variant_body
.push_parsed("bincode::Decode::decode(&mut decoder)?,")?;
}
}
variant_body.punct(':');
if field.attributes().has_attribute(FieldAttribute::WithSerde)? {
variant_body
.push_parsed("<bincode::serde::Compat<_> as bincode::Decode>::decode(&mut decoder)?.0,")?;
} else {
variant_body
.push_parsed("bincode::Decode::decode(&mut decoder)?,")?;
}
}
Ok(())
})?;
Ok(())
})?;
Ok(())
})?;
variant_case.punct(',');
}
variant_case.punct(',');
}

// invalid idx
self.invalid_variant_case(&enum_name, variant_case)
})?;
// invalid idx
self.invalid_variant_case(&enum_name, variant_case)
})?;
}
Ok(())
})?;
Ok(())
Expand All @@ -267,54 +280,58 @@ impl DeriveEnum {
.with_arg("mut decoder", "D")
.with_return_type("core::result::Result<Self, bincode::error::DecodeError>")
.body(|fn_builder| {
fn_builder
.push_parsed("let variant_index = <u32 as bincode::Decode>::decode(&mut decoder)?;")?;
fn_builder.push_parsed("match variant_index")?;
fn_builder.group(Delimiter::Brace, |variant_case| {
for (mut variant_index, variant) in self.iter_fields() {
// idx => Ok(..)
if variant_index.len() > 1 {
variant_case.push_parsed("x if x == ")?;
variant_case.extend(variant_index);
} else {
variant_case.push(variant_index.remove(0));
}
variant_case.puncts("=>");
variant_case.ident_str("Ok");
variant_case.group(Delimiter::Parenthesis, |variant_case_body| {
// Self::Variant { }
// Self::Variant { 0: ..., 1: ... 2: ... },
// Self::Variant { a: ..., b: ... c: ... },
variant_case_body.ident_str("Self");
variant_case_body.puncts("::");
variant_case_body.ident(variant.name.clone());
if self.variants.is_empty() {
fn_builder.push_parsed("core::result::Result::Err(bincode::error::DecodeError::EmptyEnum { type_name: core::any::type_name::<Self>() })")?;
} else {
fn_builder
.push_parsed("let variant_index = <u32 as bincode::Decode>::decode(&mut decoder)?;")?;
fn_builder.push_parsed("match variant_index")?;
fn_builder.group(Delimiter::Brace, |variant_case| {
for (mut variant_index, variant) in self.iter_fields() {
// idx => Ok(..)
if variant_index.len() > 1 {
variant_case.push_parsed("x if x == ")?;
variant_case.extend(variant_index);
} else {
variant_case.push(variant_index.remove(0));
}
variant_case.puncts("=>");
variant_case.ident_str("Ok");
variant_case.group(Delimiter::Parenthesis, |variant_case_body| {
// Self::Variant { }
// Self::Variant { 0: ..., 1: ... 2: ... },
// Self::Variant { a: ..., b: ... c: ... },
variant_case_body.ident_str("Self");
variant_case_body.puncts("::");
variant_case_body.ident(variant.name.clone());

variant_case_body.group(Delimiter::Brace, |variant_body| {
let is_tuple = matches!(variant.fields, Fields::Tuple(_));
for (idx, field) in variant.fields.names().into_iter().enumerate() {
if is_tuple {
variant_body.lit_usize(idx);
} else {
variant_body.ident(field.unwrap_ident().clone());
variant_case_body.group(Delimiter::Brace, |variant_body| {
let is_tuple = matches!(variant.fields, Fields::Tuple(_));
for (idx, field) in variant.fields.names().into_iter().enumerate() {
if is_tuple {
variant_body.lit_usize(idx);
} else {
variant_body.ident(field.unwrap_ident().clone());
}
variant_body.punct(':');
if field.attributes().has_attribute(FieldAttribute::WithSerde)? {
variant_body
.push_parsed("<bincode::serde::BorrowCompat<_> as bincode::BorrowDecode>::borrow_decode(&mut decoder)?.0,")?;
} else {
variant_body.push_parsed("bincode::de::BorrowDecode::borrow_decode(&mut decoder)?,")?;
}
}
variant_body.punct(':');
if field.attributes().has_attribute(FieldAttribute::WithSerde)? {
variant_body
.push_parsed("<bincode::serde::BorrowCompat<_> as bincode::BorrowDecode>::borrow_decode(&mut decoder)?.0,")?;
} else {
variant_body.push_parsed("bincode::de::BorrowDecode::borrow_decode(&mut decoder)?,")?;
}
}
Ok(())
})?;
Ok(())
})?;
Ok(())
})?;
variant_case.punct(',');
}
variant_case.punct(',');
}

// invalid idx
self.invalid_variant_case(&enum_name, variant_case)
})?;
// invalid idx
self.invalid_variant_case(&enum_name, variant_case)
})?;
}
Ok(())
})?;
Ok(())
Expand Down
6 changes: 6 additions & 0 deletions src/error.rs
View file
Expand Up @@ -116,6 +116,12 @@ pub enum DecodeError {
found: usize,
},

/// Tried to decode an enum with no variants
EmptyEnum {
/// The type that was being decoded
type_name: &'static str,
},

/// The decoder tried to decode a `CStr` or `CString`, but the incoming data contained a 0 byte
#[cfg(feature = "std")]
CStrNulError {
Expand Down
18 changes: 18 additions & 0 deletions tests/derive.rs
View file
Expand Up @@ -251,3 +251,21 @@ fn test_macro_newtype() {
assert_eq!(len, newtype_len);
}
}

#[derive(bincode::Encode, bincode::Decode, Debug)]
pub enum EmptyEnum {}

#[derive(bincode::Encode, bincode::BorrowDecode, Debug)]
pub enum BorrowedEmptyEnum {}

#[test]
fn test_empty_enum_decode() {
let err =
bincode::decode_from_slice::<EmptyEnum, _>(&[], Configuration::standard()).unwrap_err();
assert_eq!(
err,
bincode::error::DecodeError::EmptyEnum {
type_name: "derive::EmptyEnum"
}
);
}

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