deer: implement Deserialize for core::ops

libs/deer/src/error.rs

@@ -63,6 +63,7 @@ use core::{
     fmt::{self, Debug, Display, Formatter},
 };
 
+pub use duplicate::{DuplicateField, DuplicateFieldError, DuplicateKey, DuplicateKeyError};
 use error_stack::{Context, Frame, IntoReport, Report, Result};
 pub use extra::{
     ArrayLengthError, ExpectedLength, ObjectItemsExtraError, ObjectLengthError, ReceivedKey,
@@ -80,6 +81,7 @@ pub use value::{MissingError, ReceivedValue, ValueError};
 
 use crate::error::serialize::{impl_serialize, Export};
 
+mod duplicate;
 mod extra;
 mod internal;
 mod location;
@@ -469,3 +471,18 @@ impl<C: Context> ReportExt<C> for Report<C> {
         Export::new(self)
     }
 }
+
+pub(crate) trait ResultExtPrivate<C: Context> {
+    fn extend_one(&mut self, error: Report<C>);
+}
+
+impl<T, C: Context> ResultExtPrivate<C> for Result<T, C> {
+    fn extend_one(&mut self, error: Report<C>) {
+        match self {
+            Err(errors) => {
+                errors.extend_one(error);
+            }
+            errors => *errors = Err(error),
+        }
+    }
+}

libs/deer/src/error/duplicate.rs

@@ -0,0 +1,113 @@
+use alloc::string::String;
+use core::{
+    fmt,
+    fmt::{Display, Formatter},
+};
+
+use crate::{
+    error::{ErrorProperties, ErrorProperty, Id, Location, Namespace, Variant, NAMESPACE},
+    id,
+};
+
+pub struct DuplicateField(&'static str);
+
+impl DuplicateField {
+    #[must_use]
+    pub const fn new(name: &'static str) -> Self {
+        Self(name)
+    }
+}
+
+impl ErrorProperty for DuplicateField {
+    type Value<'a> = Option<&'static str> where Self: 'a;
+
+    fn key() -> &'static str {
+        "field"
+    }
+
+    fn value<'a>(mut stack: impl Iterator<Item = &'a Self>) -> Self::Value<'a> {
+        stack.next().map(|field| field.0)
+    }
+}
+
+#[derive(Debug)]
+pub struct DuplicateFieldError;
+
+impl Variant for DuplicateFieldError {
+    type Properties = (Location, DuplicateField);
+
+    const ID: Id = id!["duplicate", "field"];
+    const NAMESPACE: Namespace = NAMESPACE;
+
+    fn message(
+        &self,
+        fmt: &mut Formatter,
+        properties: &<Self::Properties as ErrorProperties>::Value<'_>,
+    ) -> fmt::Result {
+        let (_, field) = properties;
+
+        if let Some(field) = field {
+            write!(fmt, "duplicate field `{field}`")
+        } else {
+            Display::fmt(self, fmt)
+        }
+    }
+}
+
+impl Display for DuplicateFieldError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        f.write_str("duplicate field")
+    }
+}
+
+pub struct DuplicateKey(String);
+
+impl DuplicateKey {
+    pub fn new(key: impl Into<String>) -> Self {
+        Self(key.into())
+    }
+}
+
+impl ErrorProperty for DuplicateKey {
+    type Value<'a> = Option<&'a str> where Self: 'a;
+
+    fn key() -> &'static str {
+        "key"
+    }
+
+    fn value<'a>(mut stack: impl Iterator<Item = &'a Self>) -> Self::Value<'a> {
+        stack.next().map(|key| key.0.as_str())
+    }
+}
+
+#[derive(Debug)]
+pub struct DuplicateKeyError;
+
+impl Variant for DuplicateKeyError {
+    type Properties = (Location, DuplicateKey);
+
+    const ID: Id = id!["duplicate", "key"];
+    const NAMESPACE: Namespace = NAMESPACE;
+
+    fn message(
+        &self,
+        fmt: &mut Formatter,
+        properties: &<Self::Properties as ErrorProperties>::Value<'_>,
+    ) -> fmt::Result {
+        let (_, key) = properties;
+
+        if let Some(key) = key {
+            write!(fmt, "duplicate key `{key}`")
+        } else {
+            Display::fmt(self, fmt)
+        }
+    }
+}
+
+impl Display for DuplicateKeyError {
+    fn fmt(&self, f: &mut Formatter<'_>) -> fmt::Result {
+        f.write_str("duplicate key")
+    }
+}
+
+// TODO: unit test

libs/deer/src/helpers.rs

@@ -1,8 +1,10 @@
 use error_stack::{Result, ResultExt};
+use serde::{ser::SerializeMap, Serialize, Serializer};
 
 use crate::{
     error::{DeserializeError, VisitorError},
     ext::TupleExt,
+    schema::Reference,
     Deserialize, Deserializer, Document, EnumVisitor, FieldVisitor, ObjectAccess, Reflection,
     Schema, Visitor,
 };
@@ -123,3 +125,20 @@ impl<'de> Deserialize<'de> for ExpectNone {
 }
 
 // TODO: consider adding an error attachment marker type for "short-circuit"
+
+pub struct Properties<const N: usize>(pub [(&'static str, Reference); N]);
+
+impl<const N: usize> Serialize for Properties<N> {
+    fn serialize<S>(&self, serializer: S) -> core::result::Result<S::Ok, S::Error>
+    where
+        S: Serializer,
+    {
+        let mut map = serializer.serialize_map(Some(self.0.len()))?;
+
+        for (key, value) in self.0 {
+            map.serialize_entry(key, &value)?;
+        }
+
+        map.end()
+    }
+}

libs/deer/src/impls.rs

@@ -1 +1,26 @@
+use error_stack::Result;
+
+use crate::{error::VisitorError, Deserialize, Document, OptionalVisitor};
+
 mod core;
+
+pub(crate) struct UnitVariantVisitor;
+
+impl<'de> OptionalVisitor<'de> for UnitVariantVisitor {
+    type Value = ();
+
+    fn expecting(&self) -> Document {
+        // TODO: in theory also none, cannot be expressed with current schema
+        <() as Deserialize>::reflection()
+    }
+
+    fn visit_none(self) -> Result<Self::Value, VisitorError> {
+        Ok(())
+    }
+
+    fn visit_null(self) -> Result<Self::Value, VisitorError> {
+        Ok(())
+    }
+
+    // we do not implement `visit_some` because we do not allow for some values
+}

libs/deer/src/impls/core.rs

@@ -6,6 +6,7 @@ mod cmp;
 mod marker;
 mod mem;
 mod num;
+mod ops;
 mod option;
 mod result;
 mod string;