Merge pull request #4857 from Tibo-Ulens/fix/impl-aschangeset-on-ref-option

Implement AsChangeset on &Option<T>

Author: weiznich

diesel/src/query_builder/update_statement/changeset.rs

@@ -38,6 +38,18 @@ impl<T: AsChangeset> AsChangeset for Option<T> {
     }
 }
 
+impl<'update, T> AsChangeset for &'update Option<T>
+where
+    &'update T: AsChangeset,
+{
+    type Target = <&'update T as AsChangeset>::Target;
+    type Changeset = Option<<&'update T as AsChangeset>::Changeset>;
+
+    fn as_changeset(self) -> Self::Changeset {
+        self.as_ref().map(AsChangeset::as_changeset)
+    }
+}
+
 impl<Left, Right> AsChangeset for Eq<Left, Right>
 where
     Left: AssignmentTarget,

diesel_derives/tests/as_changeset.rs

@@ -928,3 +928,76 @@ fn skip_update() {
     assert_eq!(res.2, Some("green".into()));
     assert_eq!(res.3, Some("admin".into()));
 }
+
+#[test]
+fn optional_embedded_struct() {
+    #[derive(AsChangeset)]
+    #[diesel(table_name = users)]
+    struct UserAttributes<'a> {
+        hair_color: &'a str,
+        r#type: &'a str,
+    }
+
+    #[derive(AsChangeset)]
+    #[diesel(table_name = users)]
+    struct UserForm<'a> {
+        name: &'a str,
+        #[diesel(embed)]
+        attribute: Option<UserAttributes<'a>>,
+    }
+
+    let connection = &mut connection_with_sean_and_tess_in_users_table();
+
+    update(users::table.find(1))
+        .set(&UserForm {
+            name: "Jim",
+            attribute: Some(UserAttributes {
+                hair_color: "blue",
+                r#type: "super",
+            }),
+        })
+        .execute(connection)
+        .unwrap();
+
+    let expected = vec![
+        (
+            1,
+            String::from("Jim"),
+            Some(String::from("blue")),
+            Some(String::from("super")),
+        ),
+        (
+            2,
+            String::from("Tess"),
+            Some(String::from("brown")),
+            Some(String::from("admin")),
+        ),
+    ];
+    let actual = users::table.order(users::id).load(connection);
+    assert_eq!(Ok(expected), actual);
+
+    update(users::table.find(2))
+        .set(&UserForm {
+            name: "Tess",
+            attribute: None,
+        })
+        .execute(connection)
+        .unwrap();
+
+    let expected = vec![
+        (
+            1,
+            String::from("Jim"),
+            Some(String::from("blue")),
+            Some(String::from("super")),
+        ),
+        (
+            2,
+            String::from("Tess"),
+            Some(String::from("brown")),
+            Some(String::from("admin")),
+        ),
+    ];
+    let actual = users::table.order(users::id).load(connection);
+    assert_eq!(Ok(expected), actual);
+}