Add support for deriving FromSql and ToSql for structs with references

Author: alexwl

postgres-derive-test/src/compile-fail/invalid-types.rs

@@ -22,4 +22,9 @@ enum FromSqlEnum {
     Foo(i32),
 }
 
+#[derive(FromSql)]
+struct FromSqlTypeParameter<T> {
+    foo: T,
+}
+
 fn main() {}

postgres-derive-test/src/compile-fail/invalid-types.stderr

@@ -33,3 +33,9 @@ error: non-C-like enums are not supported
    |
 22 |     Foo(i32),
    |     ^^^^^^^^
+
+error: #[derive(FromSql)] does not support type parameters.
+  --> $DIR/invalid-types.rs:26:28
+   |
+26 | struct FromSqlTypeParameter<T> {
+   |                            ^^^

postgres-derive-test/src/composites.rs

@@ -215,3 +215,32 @@ fn wrong_type() {
         .unwrap_err();
     assert!(err.source().unwrap().is::<WrongType>());
 }
+
+#[test]
+fn struct_with_references() {
+    #[derive(FromSql, ToSql, Debug, PartialEq)]
+    #[postgres(name = "item")]
+    struct Item<'a, 'b: 'a> {
+        name: &'a str,
+        data: &'b [u8],
+    }
+
+    let mut conn = Client::connect("user=postgres host=localhost port=5433", NoTls).unwrap();
+    conn.batch_execute(
+        "CREATE TYPE pg_temp.item AS (
+            name TEXT,
+            data BYTEA
+        );",
+    )
+    .unwrap();
+
+    let item = Item {
+        name: "foobar",
+        data: b"12345",
+    };
+
+    let row = conn.query_one("SELECT $1::item", &[&item]).unwrap();
+    let result: Item<'_, '_> = row.get(0);
+    assert_eq!(item.name, result.name);
+    assert_eq!(item.data, result.data);
+}

postgres-derive-test/src/domains.rs

@@ -119,3 +119,23 @@ fn domain_in_composite() {
         )],
     );
 }
+
+#[test]
+fn struct_with_reference() {
+    #[derive(FromSql, ToSql, Debug, PartialEq)]
+    struct SessionId<'b>(&'b [u8]);
+
+    let mut conn = Client::connect("user=postgres host=localhost port=5433", NoTls).unwrap();
+    conn.execute(
+        "CREATE DOMAIN pg_temp.\"SessionId\" AS bytea CHECK(octet_length(VALUE) = 16);",
+        &[],
+    )
+    .unwrap();
+
+    let session_id = b"0123456789abcdef";
+    let row = conn
+        .query_one("SELECT $1::\"SessionId\"", &[&SessionId(session_id)])
+        .unwrap();
+    let result: SessionId<'_> = row.get(0);
+    assert_eq!(session_id, result.0);
+}

postgres-derive/src/fromsql.rs

@@ -8,6 +8,8 @@ use crate::composites::Field;
 use crate::enums::Variant;
 use crate::overrides::Overrides;
 
+const DEFAULT_LIFETIME: &str = "de";
+
 pub fn expand_derive_fromsql(input: DeriveInput) -> Result<TokenStream, Error> {
     let overrides = Overrides::extract(&input.attrs)?;
 
@@ -58,10 +60,33 @@ pub fn expand_derive_fromsql(input: DeriveInput) -> Result<TokenStream, Error> {
     };
 
     let ident = &input.ident;
+    let mut generics = input.generics;
+    if generics.type_params().count() > 0 {
+        return Err(Error::new_spanned(
+            &generics,
+            "#[derive(FromSql)] does not support type parameters.",
+        ));
+    }
+
+    let generics_clone = &generics.clone();
+    let (_, type_generics, _) = generics_clone.split_for_impl();
+
+    let lifetime = syn::Lifetime::new(&format!("'{}", DEFAULT_LIFETIME), Span::call_site());
+    let mut lifetime_def = syn::LifetimeDef::new(lifetime.clone());
+    let lifetimes: Vec<syn::Lifetime> = generics.lifetimes().map(|l| l.lifetime.clone()).collect();
+    lifetime_def.bounds = syn::punctuated::Punctuated::new();
+    for l in lifetimes {
+        lifetime_def.bounds.push(l);
+    }
+    generics
+        .params
+        .push(syn::GenericParam::Lifetime(lifetime_def));
+    let (impl_generics, _, _) = generics.split_for_impl();
+
     let out = quote! {
-        impl<'a> postgres_types::FromSql<'a> for #ident {
-            fn from_sql(_type: &postgres_types::Type, buf: &'a [u8])
-                        -> std::result::Result<#ident,
+        impl #impl_generics postgres_types::FromSql<#lifetime> for #ident #type_generics {
+            fn from_sql(_type: &postgres_types::Type, buf: & #lifetime [u8])
+                        -> std::result::Result<#ident #type_generics,
                                                std::boxed::Box<dyn std::error::Error +
                                                                std::marker::Sync +
                                                                std::marker::Send>> {

postgres-derive/src/tosql.rs

@@ -55,8 +55,10 @@ pub fn expand_derive_tosql(input: DeriveInput) -> Result<TokenStream, Error> {
     };
 
     let ident = &input.ident;
+    let generics = &input.generics;
+    let (impl_generics, type_generics, where_clause) = generics.split_for_impl();
     let out = quote! {
-        impl postgres_types::ToSql for #ident {
+        impl #impl_generics postgres_types::ToSql for #ident #type_generics #where_clause {
             fn to_sql(&self,
                       _type: &postgres_types::Type,
                       buf: &mut postgres_types::private::BytesMut)