From 2e08e55e0ba9130649255593bb0eea63acd1a14d Mon Sep 17 00:00:00 2001
From: OriolMunoz <20519866+OriolMunoz@users.noreply.github.com>
Date: Tue, 7 Jul 2020 21:51:30 +0200
Subject: [PATCH] Support for #[sqlx(default)]

---
 sqlx-macros/src/derives/attributes.rs |  6 ++++--
 sqlx-macros/src/derives/row.rs        | 17 ++++++++++++++---
 tests/postgres/derives.rs             | 23 +++++++++++++++++++++++
 3 files changed, 41 insertions(+), 5 deletions(-)

diff --git a/sqlx-macros/src/derives/attributes.rs b/sqlx-macros/src/derives/attributes.rs
index e349f2e914..c07e006c38 100644
--- a/sqlx-macros/src/derives/attributes.rs
+++ b/sqlx-macros/src/derives/attributes.rs
@@ -42,6 +42,7 @@ pub struct SqlxContainerAttributes {
 
 pub struct SqlxChildAttributes {
     pub rename: Option<String>,
+    pub default: bool,
 }
 
 pub fn parse_container_attributes(input: &[Attribute]) -> syn::Result<SqlxContainerAttributes> {
@@ -116,6 +117,7 @@ pub fn parse_container_attributes(input: &[Attribute]) -> syn::Result<SqlxContai
 
 pub fn parse_child_attributes(input: &[Attribute]) -> syn::Result<SqlxChildAttributes> {
     let mut rename = None;
+    let mut default = false;
 
     for attr in input {
         let meta = attr
@@ -132,7 +134,7 @@ pub fn parse_child_attributes(input: &[Attribute]) -> syn::Result<SqlxChildAttri
                                 lit: Lit::Str(val),
                                 ..
                             }) if path.is_ident("rename") => try_set!(rename, val.value(), value),
-
+                            Meta::Path(path) if path.is_ident("default") => default = true,
                             u => fail!(u, "unexpected attribute"),
                         },
                         u => fail!(u, "unexpected attribute"),
@@ -143,7 +145,7 @@ pub fn parse_child_attributes(input: &[Attribute]) -> syn::Result<SqlxChildAttri
         }
     }
 
-    Ok(SqlxChildAttributes { rename })
+    Ok(SqlxChildAttributes { rename, default })
 }
 
 pub fn check_transparent_attributes(
diff --git a/sqlx-macros/src/derives/row.rs b/sqlx-macros/src/derives/row.rs
index b461cbc6f5..cd2ebd159e 100644
--- a/sqlx-macros/src/derives/row.rs
+++ b/sqlx-macros/src/derives/row.rs
@@ -81,9 +81,20 @@ fn expand_derive_from_row_struct(
         };
         let ty = &field.ty;
 
-        Some(parse_quote!(
-            let #id: #ty = row.try_get(#id_s)?;
-        ))
+        if attributes.default {
+            Some(
+                parse_quote!(let #id: #ty = row.try_get(#id_s).or_else(|e| match e {
+                sqlx_core::error::Error::ColumnNotFound(_) => {
+                    Ok(Default::default())
+                },
+                e => Err(e)
+            })?;),
+            )
+        } else {
+            Some(parse_quote!(
+                let #id: #ty = row.try_get(#id_s)?;
+            ))
+        }
     });
 
     let names = fields.iter().map(|field| &field.ident);
diff --git a/tests/postgres/derives.rs b/tests/postgres/derives.rs
index 14dacdd966..9fbbf28681 100644
--- a/tests/postgres/derives.rs
+++ b/tests/postgres/derives.rs
@@ -381,3 +381,26 @@ async fn test_from_row_with_rename() -> anyhow::Result<()> {
 
     Ok(())
 }
+
+#[cfg(feature = "macros")]
+#[sqlx_macros::test]
+async fn test_default() -> anyhow::Result<()> {
+    #[derive(Debug, sqlx::FromRow)]
+    struct HasDefault {
+        not_default: i32,
+        #[sqlx(default)]
+        default: Option<i32>,
+    }
+
+    let mut conn = new::<Postgres>().await?;
+
+    let has_default: HasDefault = sqlx::query_as(r#"SELECT 1 AS not_default"#)
+        .fetch_one(&mut conn)
+        .await?;
+    println!("{:?}", has_default);
+
+    assert_eq!(has_default.not_default, 1);
+    assert_eq!(has_default.default, None);
+
+    Ok(())
+}