From cdf3c130b235718df861ea079f03af6aa52169a1 Mon Sep 17 00:00:00 2001
From: dvermd <315743+dvermd@users.noreply.github.com>
Date: Tue, 22 Sep 2020 05:15:46 +0200
Subject: [PATCH] Add #[derive(FromRow)] for tuple struct

---
 sqlx-macros/src/derives/row.rs | 61 ++++++++++++++++++++++++++++++----
 tests/postgres/derives.rs      | 38 +++++++++++++++++++++
 2 files changed, 93 insertions(+), 6 deletions(-)

diff --git a/sqlx-macros/src/derives/row.rs b/sqlx-macros/src/derives/row.rs
index 8f03e68754..2409c7fbfe 100644
--- a/sqlx-macros/src/derives/row.rs
+++ b/sqlx-macros/src/derives/row.rs
@@ -2,7 +2,7 @@ use proc_macro2::Span;
 use quote::quote;
 use syn::{
     parse_quote, punctuated::Punctuated, token::Comma, Data, DataStruct, DeriveInput, Field,
-    Fields, FieldsNamed, Lifetime, Stmt,
+    Fields, FieldsNamed, FieldsUnnamed, Lifetime, Stmt,
 };
 
 use super::attributes::parse_child_attributes;
@@ -15,12 +15,9 @@ pub fn expand_derive_from_row(input: &DeriveInput) -> syn::Result<proc_macro2::T
         }) => expand_derive_from_row_struct(input, named),
 
         Data::Struct(DataStruct {
-            fields: Fields::Unnamed(_),
+            fields: Fields::Unnamed(FieldsUnnamed { unnamed, .. }),
             ..
-        }) => Err(syn::Error::new_spanned(
-            input,
-            "tuple structs are not supported",
-        )),
+        }) => expand_derive_from_row_struct_unnamed(input, unnamed),
 
         Data::Struct(DataStruct {
             fields: Fields::Unit,
@@ -111,3 +108,55 @@ fn expand_derive_from_row_struct(
         }
     ))
 }
+
+fn expand_derive_from_row_struct_unnamed(
+    input: &DeriveInput,
+    fields: &Punctuated<Field, Comma>,
+) -> syn::Result<proc_macro2::TokenStream> {
+    let ident = &input.ident;
+
+    let generics = &input.generics;
+
+    let (lifetime, provided) = generics
+        .lifetimes()
+        .next()
+        .map(|def| (def.lifetime.clone(), false))
+        .unwrap_or_else(|| (Lifetime::new("'a", Span::call_site()), true));
+
+    let (_, ty_generics, _) = generics.split_for_impl();
+
+    let mut generics = generics.clone();
+    generics.params.insert(0, parse_quote!(R: sqlx::Row));
+
+    if provided {
+        generics.params.insert(0, parse_quote!(#lifetime));
+    }
+
+    let predicates = &mut generics.make_where_clause().predicates;
+
+    predicates.push(parse_quote!(usize: sqlx::ColumnIndex<R>));
+
+    for field in fields {
+        let ty = &field.ty;
+
+        predicates.push(parse_quote!(#ty: sqlx::decode::Decode<#lifetime, R::Database>));
+        predicates.push(parse_quote!(#ty: sqlx::types::Type<R::Database>));
+    }
+
+    let (impl_generics, _, where_clause) = generics.split_for_impl();
+
+    let gets = fields
+        .iter()
+        .enumerate()
+        .map(|(idx, _)| quote!(row.try_get(#idx)?));
+
+    Ok(quote!(
+        impl #impl_generics sqlx::FromRow<#lifetime, R> for #ident #ty_generics #where_clause {
+            fn from_row(row: &#lifetime R) -> sqlx::Result<Self> {
+                Ok(#ident (
+                    #(#gets),*
+                ))
+            }
+        }
+    ))
+}
diff --git a/tests/postgres/derives.rs b/tests/postgres/derives.rs
index bd45d84335..92a63e563f 100644
--- a/tests/postgres/derives.rs
+++ b/tests/postgres/derives.rs
@@ -404,6 +404,44 @@ async fn test_from_row_with_rename() -> anyhow::Result<()> {
     Ok(())
 }
 
+#[cfg(feature = "macros")]
+#[sqlx_macros::test]
+async fn test_from_row_tuple() -> anyhow::Result<()> {
+    let mut conn = new::<Postgres>().await?;
+
+    #[derive(Debug, sqlx::FromRow)]
+    struct Account(i32, String);
+
+    let account: Account = sqlx::query_as(
+        "SELECT * from (VALUES (1, 'Herp Derpinson')) accounts(id, name) where id = $1",
+    )
+    .bind(1_i32)
+    .fetch_one(&mut conn)
+    .await?;
+
+    assert_eq!(account.0, 1);
+    assert_eq!(account.1, "Herp Derpinson");
+
+    // A _single_ lifetime may be used but only when using the lowest-level API currently (Query::fetch)
+
+    #[derive(sqlx::FromRow)]
+    struct RefAccount<'a>(i32, &'a str);
+
+    let mut cursor = sqlx::query(
+        "SELECT * from (VALUES (1, 'Herp Derpinson')) accounts(id, name) where id = $1",
+    )
+    .bind(1_i32)
+    .fetch(&mut conn);
+
+    let row = cursor.try_next().await?.unwrap();
+    let account = RefAccount::from_row(&row)?;
+
+    assert_eq!(account.0, 1);
+    assert_eq!(account.1, "Herp Derpinson");
+
+    Ok(())
+}
+
 #[cfg(feature = "macros")]
 #[sqlx_macros::test]
 async fn test_default() -> anyhow::Result<()> {