Improve DataObject.save() generation

butane/tests/basic.rs

@@ -74,6 +74,12 @@ impl HasOnlyPk {
     }
 }
 
+#[model]
+#[derive(Default)]
+struct HasOnlyAutoPk {
+    id: AutoPk<i64>,
+}
+
 #[model]
 #[derive(Debug, Default, PartialEq, Clone)]
 pub struct SelfReferential {
@@ -235,12 +241,27 @@ testall!(auto_pk);
 fn only_pk(conn: Connection) {
     let mut obj = HasOnlyPk::new(1);
     obj.save(&conn).unwrap();
+    assert_eq!(obj.id, 1);
     // verify we can still save the object even though it has no
     // fields to modify
     obj.save(&conn).unwrap();
+    // verify it didnt get a new id
+    assert_eq!(obj.id, 1);
 }
 testall!(only_pk);
 
+fn only_auto_pk(conn: Connection) {
+    let mut obj = HasOnlyAutoPk::default();
+    obj.save(&conn).unwrap();
+    let pk = obj.id;
+    // verify we can still save the object even though it has no
+    // fields to modify
+    obj.save(&conn).unwrap();
+    // verify it didnt get a new id
+    assert_eq!(obj.id, pk);
+}
+testall!(only_auto_pk);
+
 fn basic_committed_transaction(mut conn: Connection) {
     let tr = conn.transaction().unwrap();
 

butane_core/src/codegen/dbobj.rs

@@ -36,8 +36,16 @@ pub fn impl_dbobject(ast_struct: &ItemStruct, config: &Config) -> TokenStream2 {
     let values: Vec<TokenStream2> = push_values(ast_struct, |_| true);
     let insert_cols = columns(ast_struct, |f| !is_auto(f));
 
-    let save_core = if is_auto(&pk_field) {
-        let pkident = pk_field.ident.clone().unwrap();
+    let save_core = if auto_pk && values.len() == 1 {
+        quote!(
+            if !butane::PrimaryKeyType::is_valid(self.pk()) {
+                let pk = conn.insert_returning_pk(Self::TABLE, &[], &pkcol, &[])?;
+                Some(butane::FromSql::from_sql(pk)?)
+            } else {
+                None
+            };
+        )
+    } else if auto_pk {
         let values_no_pk: Vec<TokenStream2> = push_values(ast_struct, |f: &Field| f != &pk_field);
         let save_cols = columns(ast_struct, |f| !is_auto(f) && f != &pk_field);
         quote!(
@@ -47,32 +55,33 @@ pub fn impl_dbobject(ast_struct: &ItemStruct, config: &Config) -> TokenStream2 {
             // keys, but butane isn't well set up to take advantage of that, including missing
             // support for constraints and the `insert_or_update` method not providing a way to
             // retrieve the pk.
-            if (butane::PrimaryKeyType::is_valid(&self.#pkident)) {
+            if butane::PrimaryKeyType::is_valid(self.pk()) {
                 #(#values_no_pk)*
-                if values.len() > 0 {
-                    conn.update(
-                        Self::TABLE,
-                        pkcol,
-                        butane::ToSql::to_sql_ref(self.pk()),
-                        &[#save_cols],
-                        &values,
-                    )?;
-                }
+                conn.update(
+                    Self::TABLE,
+                    pkcol,
+                    butane::ToSql::to_sql_ref(self.pk()),
+                    &[#save_cols],
+                    &values,
+                )?;
+                None
             } else {
                 #(#values)*
                 let pk = conn.insert_returning_pk(Self::TABLE, &[#insert_cols], &pkcol, &values)?;
-                self.#pkident = butane::FromSql::from_sql(pk)?;
-            }
+                Some(butane::FromSql::from_sql(pk)?)
+            };
         )
     } else {
         // do an upsert
         quote!(
-            #(#values)*
-            conn.insert_or_replace(Self::TABLE, &[#insert_cols], &pkcol, &values)?;
+            {
+                #(#values)*
+                conn.insert_or_replace(Self::TABLE, &[#insert_cols], &pkcol, &values)?;
+                None
+            };
         )
     };
 
-    let numdbfields = fields(ast_struct).filter(|f| is_row_field(f)).count();
     let many_save: TokenStream2 = fields(ast_struct)
         .filter(|f| is_many_to_many(f))
         .map(|f| {
@@ -93,8 +102,12 @@ pub fn impl_dbobject(ast_struct: &ItemStruct, config: &Config) -> TokenStream2 {
         .collect();
 
     let dataresult = impl_dataresult(ast_struct, tyname, config);
+    // Note the many impls following DataObject can not be generic because they implement for T and &T,
+    // which become conflicting types as &T is included in T.
+    // https://stackoverflow.com/questions/66241700
     quote!(
-                #dataresult
+        #dataresult
+
         impl butane::DataObject for #tyname {
             type PKType = #pktype;
             type Fields = #fields_type;
@@ -106,11 +119,16 @@ pub fn impl_dbobject(ast_struct: &ItemStruct, config: &Config) -> TokenStream2 {
             }
             fn save(&mut self, conn: &impl butane::db::ConnectionMethods) -> butane::Result<()> {
                 //future perf improvement use an array on the stack
-                let mut values: Vec<butane::SqlValRef> = Vec::with_capacity(#numdbfields);
+                let mut values: Vec<butane::SqlValRef> = Vec::with_capacity(
+                    <Self as butane::DataResult>::COLUMNS.len()
+                );
                 let pkcol = butane::db::Column::new(
-                    #pklit,
-                    <#pktype as butane::FieldType>::SQLTYPE);
-                #save_core
+                    Self::PKCOL,
+                    <Self::PKType as butane::FieldType>::SQLTYPE);
+                let new_pk = #save_core
+                if let Some(new_pk) = new_pk {
+                    self.#pkident = new_pk;
+                }
                 #many_save
                 Ok(())
             }