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use facet_core::{StructType, Type, UserType};
use facet_reflect::Partial;
use crate::{
DeserializeError, DeserializeErrorKind, FormatDeserializer, ParseEventKind, ScalarValue,
SpanGuard, ValueMeta, deserializer::entry::MetaSource,
};
/// Look up a field by name using precomputed TypePlan if available, otherwise linear scan.
///
/// The TypePlan's FieldLookup is precomputed at `Partial::alloc()` time and provides
/// O(1) or O(log n) lookup. If no TypePlan is available (custom deserialization frames),
/// this falls back to a linear scan through struct fields.
#[inline]
fn lookup_field<const BORROW: bool>(
wip: &Partial<'_, BORROW>,
struct_def: &'static StructType,
name: &str,
) -> Option<usize> {
// Try precomputed lookup from TypePlan first
if let Some(plan) = wip.struct_plan() {
return plan.field_lookup.find(name, wip.type_plan_core());
}
// Fallback: linear scan through fields (for frames without TypePlan)
struct_def
.fields
.iter()
.enumerate()
.find(|(_, f)| f.effective_name() == name || f.alias == Some(name))
.map(|(i, _)| i)
}
impl<'parser, 'input, const BORROW: bool> FormatDeserializer<'parser, 'input, BORROW> {
/// Deserialize a struct without flattened fields (simple case).
#[inline(never)]
pub(crate) fn deserialize_struct_simple(
&mut self,
wip: Partial<'input, BORROW>,
) -> Result<Partial<'input, BORROW>, DeserializeError> {
#[cfg(feature = "stacker")]
{
stacker::maybe_grow(1024 * 1024, 8 * 1024 * 1024, || {
self.deserialize_struct_simple_inner(wip)
})
}
#[cfg(not(feature = "stacker"))]
{
self.deserialize_struct_simple_inner(wip)
}
}
#[inline(never)]
fn deserialize_struct_simple_inner(
&mut self,
mut wip: Partial<'input, BORROW>,
) -> Result<Partial<'input, BORROW>, DeserializeError> {
use facet_core::Characteristic;
// Get struct fields for lookup (needed before hint)
let struct_def = match &wip.shape().ty {
Type::User(UserType::Struct(def)) => def,
_ => {
return Err(self.mk_err(
&wip,
DeserializeErrorKind::Unsupported {
message: format!("expected struct type but got {:?}", wip.shape().ty)
.into(),
},
));
}
};
// Hint to non-self-describing parsers how many fields to expect
if self.is_non_self_describing() {
self.parser.hint_struct_fields(struct_def.fields.len());
}
let struct_type_has_default = wip.shape().is(Characteristic::Default);
// Peek at the next event first to handle EOF and null gracefully
let maybe_event = self.peek_event_opt()?;
// Handle EOF (empty input / comment-only files): use Default if available
if maybe_event.is_none() {
if struct_type_has_default {
let _guard = SpanGuard::new(self.last_span);
wip = wip.set_default()?;
return Ok(wip);
}
return Err(self.mk_err(
&wip,
DeserializeErrorKind::UnexpectedEof { expected: "value" },
));
}
// Handle Scalar(Null): use Default if available
if let Some(ref event) = maybe_event
&& matches!(event.kind, ParseEventKind::Scalar(ScalarValue::Null))
&& struct_type_has_default
{
let _ = self.expect_event("null")?;
let _guard = SpanGuard::new(self.last_span);
wip = wip.set_default()?;
return Ok(wip);
}
let event = self.expect_event("value")?;
if !matches!(event.kind, ParseEventKind::StructStart(_)) {
return Err(self.mk_err(
&wip,
DeserializeErrorKind::UnexpectedToken {
expected: "struct start",
got: event.kind_name().into(),
},
));
}
let deny_unknown_fields = wip.struct_plan().unwrap().deny_unknown_fields;
let mut ordered_field_index = 0usize;
loop {
let event = self.expect_event("value")?;
let _guard = SpanGuard::new(self.last_span);
trace!(
?event,
"deserialize_struct_simple: loop iteration, got event"
);
match event.kind {
ParseEventKind::StructEnd => {
break;
}
ParseEventKind::OrderedField => {
// Non-self-describing formats emit OrderedField events in order
let idx = ordered_field_index;
ordered_field_index += 1;
if idx < struct_def.fields.len() {
wip = wip
.begin_nth_field(idx)?
.with(|w| self.deserialize_into(w, MetaSource::FromEvents))?
.end()?;
}
}
ParseEventKind::FieldKey(key) => {
trace!(?key, "deserialize_struct_simple: got FieldKey");
// Unit keys don't make sense for struct fields
let key_name = match key.name() {
Some(name) => name.as_ref(),
None => {
// Skip unit keys in struct context
self.skip_value()?;
continue;
}
};
// Look up field by name/alias using precomputed TypePlan lookup
if let Some(idx) = lookup_field(&wip, struct_def, key_name) {
trace!(
idx,
field_name = struct_def.fields[idx].name,
"deserialize_struct_simple: matched field"
);
// Extract metadata from key for metadata containers
let mut meta_builder = ValueMeta::builder();
if let Some(lines) = key.doc() {
meta_builder = meta_builder.doc(
lines
.iter()
.map(|s| std::borrow::Cow::Owned(s.to_string()))
.collect(),
);
}
if let Some(t) = key.tag() {
meta_builder = meta_builder.tag(std::borrow::Cow::Owned(t.to_string()));
}
let meta = meta_builder.build();
wip = wip.begin_nth_field(idx)?;
wip = self.deserialize_into(wip, MetaSource::Owned(meta))?;
let _guard = SpanGuard::new(self.last_span);
wip = wip.end()?;
continue;
}
if deny_unknown_fields {
return Err(self.mk_err(
&wip,
DeserializeErrorKind::UnknownField {
field: key_name.to_owned().into(),
suggestion: None,
},
));
} else {
// Unknown field - skip it
trace!(field_name = ?key_name, "deserialize_struct_simple: skipping unknown field");
self.skip_value()?;
}
}
other => {
return Err(self.mk_err(
&wip,
DeserializeErrorKind::UnexpectedToken {
expected: "field key or struct end",
got: other.kind_name().into(),
},
));
}
}
}
// In deferred mode, skip validation - finish_deferred() will handle it.
// This allows formats like TOML to reopen tables and set more fields later.
if wip.is_deferred() {
return Ok(wip);
}
// Defaults for missing fields are applied automatically by facet-reflect's
// fill_defaults() when build() or end() is called.
Ok(wip)
}
}