libsql: port row deserializer from rust client

libsql/src/deserialize_row.rs

@@ -0,0 +1,99 @@
+use crate::{Row, Value};
+use serde::de::{
+    value::{Error as DeError, SeqDeserializer},
+    Error, IntoDeserializer, MapAccess, Visitor,
+};
+use serde::{Deserialize, Deserializer};
+
+struct RowDeserializer<'de> {
+    row: &'de Row,
+}
+
+impl<'de> Deserializer<'de> for RowDeserializer<'de> {
+    type Error = DeError;
+
+    fn deserialize_any<V>(self, _visitor: V) -> Result<V::Value, Self::Error>
+    where
+        V: Visitor<'de>,
+    {
+        Err(DeError::custom("Expects a struct"))
+    }
+
+    fn deserialize_struct<V>(
+        self,
+        _name: &'static str,
+        _fields: &'static [&'static str],
+        visitor: V,
+    ) -> Result<V::Value, Self::Error>
+    where
+        V: Visitor<'de>,
+    {
+        struct RowMapAccess<'a> {
+            row: &'a Row,
+            idx: std::ops::Range<usize>,
+            value: Option<Value>,
+        }
+
+        impl<'de> MapAccess<'de> for RowMapAccess<'de> {
+            type Error = DeError;
+
+            fn next_key_seed<K>(&mut self, seed: K) -> Result<Option<K::Value>, Self::Error>
+            where
+                K: serde::de::DeserializeSeed<'de>,
+            {
+                match self.idx.next() {
+                    None => Ok(None),
+                    Some(i) => {
+                        let value = self
+                            .row
+                            .get_value(i as i32)
+                            .map_err(|e| DeError::custom(e))?;
+                        self.value = Some(value);
+                        self.row
+                            .column_name(i as i32)
+                            .map(|name| seed.deserialize(name.into_deserializer()))
+                            .transpose()
+                    }
+                }
+            }
+
+            fn next_value_seed<V>(&mut self, seed: V) -> Result<V::Value, Self::Error>
+            where
+                V: serde::de::DeserializeSeed<'de>,
+            {
+                let value = self
+                    .value
+                    .take()
+                    .ok_or(DeError::custom("Expects a value but row is exhausted"))?;
+
+                match value {
+                    Value::Text(value) => seed.deserialize(value.into_deserializer()),
+                    Value::Null => seed.deserialize(().into_deserializer()),
+                    Value::Integer(value) => seed.deserialize(value.into_deserializer()),
+                    Value::Real(value) => seed.deserialize(value.into_deserializer()),
+                    Value::Blob(value) => {
+                        let seq = SeqDeserializer::new(value.iter().cloned());
+                        seed.deserialize(seq)
+                    }
+                }
+            }
+        }
+
+        visitor.visit_map(RowMapAccess {
+            row: self.row,
+            idx: 0..self.row.inner.column_count(),
+            value: None,
+        })
+    }
+
+    serde::forward_to_deserialize_any! {
+        bool i8 i16 i32 i64 i128 u8 u16 u32 u64 u128 f32 f64 char str string
+        bytes byte_buf option unit unit_struct newtype_struct seq tuple
+        tuple_struct map enum identifier ignored_any
+    }
+}
+
+pub fn from_row<'de, T: Deserialize<'de>>(row: &'de Row) -> Result<T, DeError> {
+    let de = RowDeserializer { row };
+    T::deserialize(de)
+}

libsql/src/hrana/mod.rs

@@ -190,6 +190,10 @@ impl RowInner for Row {
             Err(crate::Error::ColumnNotFound(idx))
         }
     }
+
+    fn column_count(&self) -> usize {
+        self.cols.len()
+    }
 }
 
 fn bind_params(params: Params, stmt: &mut Stmt) {

libsql/src/lib.rs

@@ -87,6 +87,9 @@ mod statement;
 mod transaction;
 mod value;
 
+#[cfg(feature = "serde")]
+pub mod deserialize_row;
+
 pub use value::{Value, ValueRef, ValueType};
 
 cfg_hrana! {

libsql/src/local/impls.rs

@@ -162,6 +162,10 @@ impl RowInner for LibsqlRow {
     fn column_type(&self, idx: i32) -> Result<ValueType> {
         self.0.column_type(idx).map(ValueType::from)
     }
+
+    fn column_count(&self) -> usize {
+        self.0.stmt.column_count()
+    }
 }
 
 impl fmt::Debug for LibsqlRow {

libsql/src/replication/connection.rs

@@ -648,6 +648,10 @@ impl RowInner for RemoteRow {
             .map(ValueType::from)
             .ok_or(Error::InvalidColumnType)
     }
+
+    fn column_count(&self) -> usize {
+        self.1.len()
+    }
 }
 
 pub(super) struct RemoteTx(pub(super) Option<RemoteConnection>);

libsql/src/rows.rs

@@ -219,4 +219,5 @@ pub(crate) trait RowInner: fmt::Debug {
     fn column_str(&self, idx: i32) -> Result<&str>;
     fn column_name(&self, idx: i32) -> Option<&str>;
     fn column_type(&self, idx: i32) -> Result<ValueType>;
+    fn column_count(&self) -> usize;
 }

libsql/tests/integration_tests.rs

@@ -360,3 +360,44 @@ async fn debug_print_row() {
         "{Some(\"id\"): (Integer, 123), Some(\"name\"): (Text, \"potato\"), Some(\"score\"): (Real, 3.14), Some(\"data\"): (Blob, 4), Some(\"age\"): (Null, ())}"
     );
 }
+
+#[cfg(feature = "serde")]
+#[tokio::test]
+async fn deserialize_row() {
+    let db = Database::open(":memory:").unwrap();
+    let conn = db.connect().unwrap();
+    let _ = conn
+        .execute(
+            "CREATE TABLE users (id INTEGER, name TEXT, score REAL, data BLOB, age INTEGER)",
+            (),
+        )
+        .await;
+    conn.execute("INSERT INTO users (id, name, score, data, age) VALUES (123, \"potato\", 3.14, X'deadbeef', NULL)", ())
+    .await
+    .unwrap();
+
+    use serde::Deserialize;
+
+    #[derive(Deserialize, Debug)]
+    struct Data {
+        id: i64,
+        name: String,
+        score: f64,
+        data: Vec<u8>,
+        age: (),
+    }
+
+    let row = conn
+        .query("SELECT * FROM users", ())
+        .await
+        .unwrap()
+        .next()
+        .unwrap()
+        .unwrap();
+    let data: Data = libsql::deserialize_row::from_row(&row).unwrap();
+    assert_eq!(data.id, 123);
+    assert_eq!(data.name, "potato".to_string());
+    assert_eq!(data.score, 3.14);
+    assert_eq!(data.data, vec![0xde, 0xad, 0xbe, 0xef]);
+    assert_eq!(data.age, ());
+}