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feat(shape): a fixed array carries its length #22

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Merged
Kinflou merged 1 commit into from
Oct 18, 2026
Merged

feat(shape): a fixed array carries its length #22

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35 changes: 29 additions & 6 deletions src/shape.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -108,7 +108,12 @@ impl TypeDef {
pub enum TypeRef {
Prim { name: String },
Ref { name: String },
Array { of: Box<TypeRef> },
/// `len` is a fixed array's length (`u8[4]`); absent for `T[]`.
Array {
of: Box<TypeRef>,
#[serde(default, skip_serializing_if = "Option::is_none")]
len: Option<u64>,
},
Unit,
Union { of: Vec<TypeRef> },
}
Expand All @@ -131,7 +136,8 @@ pub fn type_label(ty: &TypeRef) -> String {
match ty {
TypeRef::Unit => "()".to_string(),
TypeRef::Prim { name } | TypeRef::Ref { name } => name.clone(),
TypeRef::Array { of } => format!("{}[]", type_label(of)),
TypeRef::Array { of, len: None } => format!("{}[]", type_label(of)),
TypeRef::Array { of, len: Some(n) } => format!("{}[{n}]", type_label(of)),
TypeRef::Union { of } => of.iter().map(type_label).collect::<Vec<_>>().join(" | "),
}
}
Expand All @@ -145,7 +151,10 @@ pub fn zero_value(ty: &TypeRef, types: &[TypeDef]) -> Value {
fn zero_value_seen(ty: &TypeRef, types: &[TypeDef], seen: &mut Vec<String>) -> Value {
match ty {
TypeRef::Unit => Value::Null,
TypeRef::Array { .. } => Value::Array(Vec::new()),
TypeRef::Array { len: None, .. } => Value::Array(Vec::new()),
TypeRef::Array { of, len: Some(n) } => {
Value::Array((0..*n).map(|_| zero_value_seen(of, types, seen)).collect())
}
TypeRef::Union { of } => of
.first()
.map_or(Value::Null, |t| zero_value_seen(t, types, seen)),
Expand Down Expand Up @@ -272,7 +281,8 @@ mod tests {
TypeRef::Array {
of: Box::new(TypeRef::Ref {
name: "Message".into()
})
}),
len: None
}
);
assert_eq!(
Expand Down Expand Up @@ -328,12 +338,24 @@ mod tests {
assert_eq!(
zero_value(
&TypeRef::Array {
of: Box::new(TypeRef::Unit)
of: Box::new(TypeRef::Unit),
len: None
},
&types
),
json!([])
);
// A fixed array is already its full length.
assert_eq!(
zero_value(
&TypeRef::Array {
of: Box::new(TypeRef::Prim { name: "u8".into() }),
len: Some(3)
},
&types
),
json!([0, 0, 0])
);
assert_eq!(
zero_value(
&TypeRef::Prim {
Expand Down Expand Up @@ -384,7 +406,8 @@ mod tests {
type_label(&TypeRef::Array {
of: Box::new(TypeRef::Ref {
name: "Message".into()
})
}),
len: None
}),
"Message[]"
);
Expand Down
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