Add serde::from_row_via_index

CHANGELOG.md

@@ -15,6 +15,7 @@ Procedure when bumping the version number:
 
 ### Added
 - `serde` feature
+- `serde::from_row_via_index`
 
 ### Changed
 - **(breaking)**

src/lib.rs

@@ -9,12 +9,17 @@
 // Clippy lints
 #![warn(clippy::use_self)]
 
+#[cfg(feature = "serde")]
+pub mod serde;
 pub mod simple;
 #[cfg(feature = "tokio")]
 pub mod tokio;
 
 use rusqlite::{Connection, Transaction};
 
+#[cfg(feature = "serde")]
+pub use self::serde::*;
+
 /// An action that can be performed on a [`Connection`].
 ///
 /// Both commands and queries are considered actions. Commands usually have a

src/serde.rs

@@ -0,0 +1,247 @@
+use std::{error, fmt, str::Utf8Error};
+
+use rusqlite::{
+    types::{FromSqlError, ValueRef},
+    Row,
+};
+use serde::{
+    de::{
+        self, value::BorrowedStrDeserializer, DeserializeSeed, Deserializer, MapAccess, SeqAccess,
+        Visitor,
+    },
+    forward_to_deserialize_any, Deserialize,
+};
+
+#[derive(Debug)]
+enum Error {
+    ExpectedTupleLikeBaseType,
+    Utf8(Utf8Error),
+    Rusqlite(rusqlite::Error),
+    Custom(String),
+}
+
+impl fmt::Display for Error {
+    fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        match self {
+            Self::ExpectedTupleLikeBaseType => write!(f, "expected tuple-like base type"),
+            Self::Utf8(err) => err.fmt(f),
+            Self::Rusqlite(err) => err.fmt(f),
+            Self::Custom(msg) => msg.fmt(f),
+        }
+    }
+}
+
+impl error::Error for Error {}
+
+impl de::Error for Error {
+    fn custom<T: fmt::Display>(msg: T) -> Self {
+        Self::Custom(msg.to_string())
+    }
+}
+
+impl From<Utf8Error> for Error {
+    fn from(value: Utf8Error) -> Self {
+        Self::Utf8(value)
+    }
+}
+
+impl From<rusqlite::Error> for Error {
+    fn from(value: rusqlite::Error) -> Self {
+        Self::Rusqlite(value)
+    }
+}
+
+struct ValueRefDeserializer<'de> {
+    value: ValueRef<'de>,
+}
+
+impl<'de> Deserializer<'de> for ValueRefDeserializer<'de> {
+    type Error = Error;
+
+    forward_to_deserialize_any! {
+        i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes byte_buf
+        unit unit_struct seq tuple tuple_struct map struct identifier
+        ignored_any
+    }
+
+    fn deserialize_any<V: Visitor<'de>>(self, visitor: V) -> Result<V::Value, Self::Error> {
+        match self.value {
+            ValueRef::Null => visitor.visit_unit(),
+            ValueRef::Integer(v) => visitor.visit_i64(v),
+            ValueRef::Real(v) => visitor.visit_f64(v),
+            ValueRef::Text(v) => visitor.visit_borrowed_str(std::str::from_utf8(v)?),
+            ValueRef::Blob(v) => visitor.visit_borrowed_bytes(v),
+        }
+    }
+
+    fn deserialize_bool<V: Visitor<'de>>(self, visitor: V) -> Result<V::Value, Self::Error> {
+        match self.value {
+            ValueRef::Integer(0) => visitor.visit_bool(false),
+            ValueRef::Integer(_) => visitor.visit_bool(true),
+            _ => self.deserialize_any(visitor),
+        }
+    }
+
+    fn deserialize_option<V: Visitor<'de>>(self, visitor: V) -> Result<V::Value, Self::Error> {
+        match self.value {
+            ValueRef::Null => visitor.visit_none(),
+            _ => visitor.visit_some(self),
+        }
+    }
+
+    fn deserialize_newtype_struct<V: Visitor<'de>>(
+        self,
+        _name: &'static str,
+        visitor: V,
+    ) -> Result<V::Value, Self::Error> {
+        visitor.visit_newtype_struct(self)
+    }
+
+    fn deserialize_enum<V: Visitor<'de>>(
+        self,
+        name: &'static str,
+        variants: &'static [&'static str],
+        visitor: V,
+    ) -> Result<V::Value, Self::Error> {
+        match self.value {
+            ValueRef::Text(v) => {
+                let v = BorrowedStrDeserializer::new(std::str::from_utf8(v)?);
+                v.deserialize_enum(name, variants, visitor)
+            }
+            _ => self.deserialize_any(visitor),
+        }
+    }
+}
+
+struct IndexedRowDeserializer<'de, 'stmt> {
+    row: &'de Row<'stmt>,
+}
+
+impl<'de> Deserializer<'de> for IndexedRowDeserializer<'de, '_> {
+    type Error = Error;
+
+    forward_to_deserialize_any! {
+        bool i8 i16 i32 i64 u8 u16 u32 u64 f32 f64 char str string bytes
+        byte_buf option unit unit_struct map enum identifier ignored_any
+    }
+
+    fn deserialize_any<V: Visitor<'de>>(self, _visitor: V) -> Result<V::Value, Self::Error> {
+        Err(Error::ExpectedTupleLikeBaseType)
+    }
+
+    fn deserialize_newtype_struct<V: Visitor<'de>>(
+        self,
+        _name: &'static str,
+        visitor: V,
+    ) -> Result<V::Value, Self::Error> {
+        visitor.visit_newtype_struct(self)
+    }
+
+    fn deserialize_seq<V: Visitor<'de>>(self, visitor: V) -> Result<V::Value, Self::Error> {
+        visitor.visit_seq(IndexedRowSeq::new(self.row))
+    }
+
+    fn deserialize_tuple<V: Visitor<'de>>(
+        self,
+        _len: usize,
+        visitor: V,
+    ) -> Result<V::Value, Self::Error> {
+        self.deserialize_seq(visitor)
+    }
+
+    fn deserialize_tuple_struct<V: Visitor<'de>>(
+        self,
+        _name: &'static str,
+        _len: usize,
+        visitor: V,
+    ) -> Result<V::Value, Self::Error> {
+        self.deserialize_seq(visitor)
+    }
+
+    fn deserialize_struct<V: Visitor<'de>>(
+        self,
+        _name: &'static str,
+        fields: &'static [&'static str],
+        visitor: V,
+    ) -> Result<V::Value, Self::Error> {
+        visitor.visit_map(IndexedRowMap::new(self.row, fields))
+    }
+}
+
+struct IndexedRowSeq<'de, 'stmt> {
+    row: &'de Row<'stmt>,
+    next_index: usize,
+}
+
+impl<'de, 'stmt> IndexedRowSeq<'de, 'stmt> {
+    fn new(row: &'de Row<'stmt>) -> Self {
+        Self { row, next_index: 0 }
+    }
+}
+
+impl<'de> SeqAccess<'de> for IndexedRowSeq<'de, '_> {
+    type Error = Error;
+
+    fn next_element_seed<T>(&mut self, seed: T) -> Result<Option<T::Value>, Self::Error>
+    where
+        T: DeserializeSeed<'de>,
+    {
+        match self.row.get_ref(self.next_index) {
+            Ok(value) => {
+                self.next_index += 1;
+                seed.deserialize(ValueRefDeserializer { value }).map(Some)
+            }
+            Err(rusqlite::Error::InvalidColumnIndex(_)) => Ok(None),
+            Err(err) => Err(err)?,
+        }
+    }
+}
+
+struct IndexedRowMap<'de, 'stmt> {
+    row: &'de Row<'stmt>,
+    fields: &'static [&'static str],
+    next_index: usize,
+}
+
+impl<'de, 'stmt> IndexedRowMap<'de, 'stmt> {
+    fn new(row: &'de Row<'stmt>, fields: &'static [&'static str]) -> Self {
+        Self {
+            row,
+            fields,
+            next_index: 0,
+        }
+    }
+}
+
+impl<'de> MapAccess<'de> for IndexedRowMap<'de, '_> {
+    type Error = Error;
+
+    fn next_key_seed<K>(&mut self, seed: K) -> Result<Option<K::Value>, Self::Error>
+    where
+        K: DeserializeSeed<'de>,
+    {
+        if let Some(key) = self.fields.get(self.next_index) {
+            self.next_index += 1;
+            seed.deserialize(BorrowedStrDeserializer::new(key))
+                .map(Some)
+        } else {
+            Ok(None)
+        }
+    }
+
+    fn next_value_seed<V>(&mut self, seed: V) -> Result<V::Value, Self::Error>
+    where
+        V: DeserializeSeed<'de>,
+    {
+        let value = self.row.get_ref(self.next_index - 1)?;
+        seed.deserialize(ValueRefDeserializer { value })
+    }
+}
+
+pub fn from_row_via_index<'de, T>(row: &'de Row<'_>) -> rusqlite::Result<T>
+where
+    T: Deserialize<'de>,
+{
+    T::deserialize(IndexedRowDeserializer { row })
+        .map_err(|err| FromSqlError::Other(Box::new(err)).into())
+}