feat: Add embed field attribute for AsChangeset

diesel_derives/src/as_changeset.rs

@@ -92,13 +92,18 @@ fn field_changeset_ty(
     treat_none_as_null: bool,
     lifetime: Option<proc_macro2::TokenStream>,
 ) -> syn::Type {
-    let column_name = field.column_name();
-    if !treat_none_as_null && is_option_ty(&field.ty) {
-        let field_ty = inner_of_option_ty(&field.ty);
-        parse_quote!(std::option::Option<diesel::dsl::Eq<#table_name::#column_name, #lifetime #field_ty>>)
-    } else {
+    if field.has_flag("embed") {
         let field_ty = &field.ty;
-        parse_quote!(diesel::dsl::Eq<#table_name::#column_name, #lifetime #field_ty>)
+        parse_quote!(#lifetime #field_ty)
+    } else {
+        let column_name = field.column_name();
+        if !treat_none_as_null && is_option_ty(&field.ty) {
+            let field_ty = inner_of_option_ty(&field.ty);
+            parse_quote!(std::option::Option<diesel::dsl::Eq<#table_name::#column_name, #lifetime #field_ty>>)
+        } else {
+            let field_ty = &field.ty;
+            parse_quote!(diesel::dsl::Eq<#table_name::#column_name, #lifetime #field_ty>)
+        }
     }
 }
 
@@ -109,14 +114,19 @@ fn field_changeset_expr(
     lifetime: Option<proc_macro2::TokenStream>,
 ) -> syn::Expr {
     let field_access = field.name.access();
-    let column_name = field.column_name();
-    if !treat_none_as_null && is_option_ty(&field.ty) {
-        if lifetime.is_some() {
-            parse_quote!(self#field_access.as_ref().map(|x| #table_name::#column_name.eq(x)))
+    if field.has_flag("embed") {
+        parse_quote!(#lifetime self#field_access)
+    } else {
+        let column_name = field.column_name();
+        let column: syn::Expr = parse_quote!(#table_name::#column_name);
+        if !treat_none_as_null && is_option_ty(&field.ty) {
+            if lifetime.is_some() {
+                parse_quote!(self#field_access.as_ref().map(|x| #column.eq(x)))
+            } else {
+                parse_quote!(self#field_access.map(|x| #column.eq(x)))
+            }
         } else {
-            parse_quote!(self#field_access.map(|x| #table_name::#column_name.eq(x)))
+            parse_quote!(#column.eq(#lifetime self#field_access))
         }
-    } else {
-        parse_quote!(#table_name::#column_name.eq(#lifetime self#field_access))
     }
 }

diesel_derives/src/lib.rs

@@ -70,6 +70,11 @@ use diagnostic_shim::*;
 /// annotate your struct with `#[changeset_options(treat_none_as_null =
 /// "true")]`.
 ///
+/// Your struct can also contain fields which implement `AsChangeset`. This is
+/// useful when you want to have one field map to more than one column (for
+/// example, an enum that maps to a label and a value column). Add
+/// `#[diesel(embed)]` to any such fields.
+///
 /// # Attributes
 ///
 /// ## Optional type attributes
@@ -88,9 +93,11 @@ use diagnostic_shim::*;
 /// * `#[column_name = "some_column_name"]`, overrides the column name
 /// of the current field to `some_column_name`. By default the field
 /// name is used as column name.
+/// * `#[diesel(embed)]`, specifies that the current field maps not only
+/// to single database field, but is a type that implements `AsChangeset`
 #[proc_macro_derive(
     AsChangeset,
-    attributes(table_name, primary_key, column_name, changeset_options)
+    attributes(diesel, table_name, primary_key, column_name, changeset_options)
 )]
 pub fn derive_as_changeset(input: TokenStream) -> TokenStream {
     expand_proc_macro(input, as_changeset::derive)

diesel_tests/tests/update.rs

@@ -1,5 +1,9 @@
 use crate::schema::*;
 use diesel::*;
+use diesel::{
+    expression::{bound::Bound, grouped::Grouped, operators},
+    sql_types::{Nullable, Text},
+};
 
 #[test]
 fn test_updating_single_column() {
@@ -301,3 +305,93 @@ fn upsert_with_sql_literal_for_target() {
     ];
     assert_eq!(Ok(expected_data), data);
 }
+
+#[derive(AsChangeset)]
+#[table_name = "users"]
+struct UpdateUser {
+    name: Option<String>,
+    #[diesel(embed)]
+    hair_color: HairColor,
+}
+
+#[allow(dead_code)]
+enum HairColor {
+    Bald,
+    Black,
+    White,
+    Other(String),
+}
+
+impl AsChangeset for HairColor {
+    type Target = users::table;
+    type Changeset =
+        Option<Grouped<operators::Eq<users::hair_color, Bound<Nullable<Text>, String>>>>;
+
+    fn as_changeset(self) -> Self::Changeset {
+        match self {
+            HairColor::Black => Some(users::hair_color.eq("Black".to_string())),
+            HairColor::White => Some(users::hair_color.eq("White".to_string())),
+            HairColor::Other(x) => Some(users::hair_color.eq(x)),
+            HairColor::Bald => None,
+        }
+    }
+}
+
+impl AsChangeset for &HairColor {
+    type Target = users::table;
+    type Changeset =
+        Option<Grouped<operators::Eq<users::hair_color, Bound<Nullable<Text>, String>>>>;
+
+    fn as_changeset(self) -> Self::Changeset {
+        match self {
+            HairColor::Black => Some(users::hair_color.eq("Black".to_string())),
+            HairColor::White => Some(users::hair_color.eq("White".to_string())),
+            HairColor::Other(x) => Some(users::hair_color.eq(x.clone())),
+            HairColor::Bald => None,
+        }
+    }
+}
+
+#[test]
+fn update_user_with_embed() {
+    let connection = connection_with_sean_and_tess_in_users_table();
+
+    let expected_user = User {
+        id: 1,
+        name: "Sean".to_string(),
+        hair_color: Some("Black".to_string()),
+    };
+
+    let updated_user: User = diesel::update(users::table)
+        .filter(users::id.eq(1))
+        .set(UpdateUser {
+            name: None,
+            hair_color: HairColor::Black,
+        })
+        .get_result(&connection)
+        .unwrap();
+
+    assert_eq!(expected_user, updated_user);
+}
+
+#[test]
+fn update_user_with_embed_that_sets_null() {
+    let connection = connection_with_sean_and_tess_in_users_table();
+
+    let expected_user = User {
+        id: 1,
+        name: "Sean".to_string(),
+        hair_color: None,
+    };
+
+    let updated_user: User = diesel::update(users::table)
+        .filter(users::id.eq(1))
+        .set(UpdateUser {
+            name: None,
+            hair_color: HairColor::Bald,
+        })
+        .get_result(&connection)
+        .unwrap();
+
+    assert_eq!(expected_user, updated_user);
+}