deer: implement Deserialize for &[u8] (#2389)

* feat: import from #1875

* test: byte-string

Author: indietyp

libs/deer/src/impls/core.rs

@@ -1,5 +1,6 @@
 mod array;
 mod bool;
+mod bytes;
 mod cell;
 mod cmp;
 mod floating;

libs/deer/src/impls/core/bytes.rs

@@ -0,0 +1,39 @@
+use core::marker::PhantomData;
+
+use error_stack::ResultExt;
+
+use crate::{
+    error::{DeserializeError, VisitorError},
+    Deserialize, Deserializer, Document, Reflection, Schema, Visitor,
+};
+
+struct BytesVisitor<'de>(PhantomData<fn() -> &'de ()>);
+
+impl<'de> Visitor<'de> for BytesVisitor<'de> {
+    type Value = &'de [u8];
+
+    fn expecting(&self) -> Document {
+        Self::Value::reflection()
+    }
+
+    fn visit_borrowed_bytes(self, v: &'de [u8]) -> error_stack::Result<Self::Value, VisitorError> {
+        Ok(v)
+    }
+}
+
+impl Reflection for [u8] {
+    fn schema(_: &mut Document) -> Schema {
+        // this type does not really exist in json-schema :/
+        // TODO: correct valid schema?
+        Schema::new("bytes")
+    }
+}
+
+impl<'de> Deserialize<'de> for &'de [u8] {
+    type Reflection = [u8];
+
+    fn deserialize<D: Deserializer<'de>>(de: D) -> error_stack::Result<Self, DeserializeError> {
+        de.deserialize_bytes(BytesVisitor(PhantomData))
+            .change_context(DeserializeError)
+    }
+}

libs/deer/tests/test_impls_core_bytes.rs

@@ -0,0 +1,9 @@
+use deer_desert::{assert_tokens, Token};
+
+// cannot use proptest because tokenizer does not yet support borrowed data
+#[test]
+fn bytes_ok() {
+    const EXPECTED: &[u8] = b"This is an example sentence";
+
+    assert_tokens(&EXPECTED, &[Token::BorrowedBytes(EXPECTED)]);
+}