implement error handling through notifications

Cargo.toml

@@ -27,6 +27,7 @@ serde = "1.0.136"
 serde_derive = "1.0.136"
 sea-orm = { version = "^0.9.1", features = [], default-features = false }
 actix-admin-macros = { version = "0.1.0", path = "actix_admin_macros" }
+derive_more = "0.99.17"
 
 [dev-dependencies]
 sea-orm = { version = "^0.9.1", features = [ "sqlx-sqlite", "runtime-actix-native-tls", "macros" ], default-features = true }

actix_admin_macros/src/lib.rs

@@ -67,7 +67,7 @@ pub fn derive_actix_admin_view_model(input: proc_macro::TokenStream) -> proc_mac
 
         #[async_trait(?Send)]
         impl ActixAdminViewModelTrait for Entity {
-            async fn list(db: &DatabaseConnection, page: usize, entities_per_page: usize, search: &String) -> (usize, Vec<ActixAdminModel>) {
+            async fn list(db: &DatabaseConnection, page: usize, entities_per_page: usize, search: &String) -> Result<(usize, Vec<ActixAdminModel>), ActixAdminError> {
                 let entities = Entity::list_model(db, page, entities_per_page, search).await;
                 entities
             }
@@ -82,43 +82,51 @@ pub fn derive_actix_admin_view_model(input: proc_macro::TokenStream) -> proc_mac
                 }
             } 
 
-            async fn create_entity(db: &DatabaseConnection, mut model: ActixAdminModel) -> ActixAdminModel {
+            async fn create_entity(db: &DatabaseConnection, mut model: ActixAdminModel) -> Result<ActixAdminModel, ActixAdminError> {
                 let new_model = ActiveModel::from(model.clone());
-                let insert_operation = Entity::insert(new_model).exec(db).await;
+                let insert_operation = Entity::insert(new_model).exec(db).await?;
                 
-                model
+                model.primary_key = Some(insert_operation.last_insert_id.to_string());
+
+                Ok(model)
             }
 
-            async fn get_entity(db: &DatabaseConnection, id: i32) -> ActixAdminModel {
+            async fn get_entity(db: &DatabaseConnection, id: i32) -> Result<ActixAdminModel, ActixAdminError> {
                 // TODO: separate primary key from other keys
-                let entity = Entity::find_by_id(id).one(db).await.unwrap().unwrap();
+                let entity = Entity::find_by_id(id).one(db).await?;
-                let model = ActixAdminModel::from(entity);
+                match entity {
-                model
+                    Some(e) => Ok(ActixAdminModel::from(e)),
+                    _ => Err(ActixAdminError::EntityDoesNotExistError)
+                }
             }
 
-            async fn edit_entity(db: &DatabaseConnection, id: i32, mut model: ActixAdminModel) -> ActixAdminModel {
+            async fn edit_entity(db: &DatabaseConnection, id: i32, mut model: ActixAdminModel) -> Result<ActixAdminModel, ActixAdminError> {
-                let entity: Option<Model> = Entity::find_by_id(id).one(db).await.unwrap();
+                let entity: Option<Model> = Entity::find_by_id(id).one(db).await?;
-                let mut entity: ActiveModel = entity.unwrap().into();
 
+                match entity {
+                    Some(e) => {
+                        let mut entity: ActiveModel = e.into();
                         #(#fields_for_edit_model);*;
-                let entity: Model = entity.update(db).await.unwrap();
+                        let entity: Model = entity.update(db).await?;    
-
+                        Ok(model)        
-                model
+                    },
+                    _ => Err(ActixAdminError::EntityDoesNotExistError)
+                }
             }
 
-            async fn delete_entity(db: &DatabaseConnection, id: i32) -> bool {
+            async fn delete_entity(db: &DatabaseConnection, id: i32) -> Result<bool, ActixAdminError> {
                 let result = Entity::delete_by_id(id).exec(db).await;
 
                 match result {
-                    Ok(_) => true,
+                    Ok(_) => Ok(true),
-                    Err(_) => false
+                    Err(_) => Err(ActixAdminError::DeleteError)
                 }
             }
 
-            async fn get_select_lists(db: &DatabaseConnection) -> HashMap<String, Vec<(String, String)>> {
+            async fn get_select_lists(db: &DatabaseConnection) -> Result<HashMap<String, Vec<(String, String)>>, ActixAdminError> {
-                hashmap![
+                Ok(hashmap![
                     #(#select_lists),*
-                ]
+                ])
             }
 
             fn get_entity_name() -> String {
@@ -173,7 +181,7 @@ pub fn derive_actix_admin_model(input: proc_macro::TokenStream) -> proc_macro::T
 
         #[async_trait]
         impl ActixAdminModelTrait for Entity {
-            async fn list_model(db: &DatabaseConnection, page: usize, posts_per_page: usize, search: &String) -> (usize, Vec<ActixAdminModel>) {
+            async fn list_model(db: &DatabaseConnection, page: usize, posts_per_page: usize, search: &String) -> Result<(usize, Vec<ActixAdminModel>), ActixAdminError> {
                 use sea_orm::{ query::* };
                 let paginator = Entity::find()
                     .filter(
@@ -182,11 +190,10 @@ pub fn derive_actix_admin_model(input: proc_macro::TokenStream) -> proc_macro::T
                     )
                     .order_by_asc(Column::Id)
                     .paginate(db, posts_per_page);
-                let num_pages = paginator.num_pages().await.ok().unwrap();
+                let num_pages = paginator.num_pages().await?;
                 let entities = paginator
                     .fetch_page(page - 1)
-                    .await
+                    .await?;
-                    .expect("could not retrieve entities");
                 let mut model_entities = Vec::new();
                 for entity in entities {
                     model_entities.push(
@@ -194,7 +201,7 @@ pub fn derive_actix_admin_model(input: proc_macro::TokenStream) -> proc_macro::T
                     );
                 }
 
-                (num_pages, model_entities)
+                Ok((num_pages, model_entities))
             }
 
             fn validate_model(model: &mut ActixAdminModel) {

actix_admin_macros/src/selectlist_fields.rs

@@ -12,15 +12,15 @@ pub fn get_select_list_from_model(_input: proc_macro::TokenStream) -> proc_macro
     let expanded = quote! {
         #[async_trait]
         impl ActixAdminSelectListTrait for Entity {
-            async fn get_key_value(db: &DatabaseConnection) -> Vec<(String, String)> {
+            async fn get_key_value(db: &DatabaseConnection) -> Result<Vec<(String, String)>, ActixAdminError> {
-                let entities = Entity::find().order_by_asc(Column::Id).all(db).await;
+                let entities = Entity::find().order_by_asc(Column::Id).all(db).await?;
                 let mut key_value = Vec::new();
             
-                for entity in entities.unwrap() {
+                for entity in entities {
                     key_value.push((entity.id.to_string(),  entity.to_string()));
                 };
                 key_value.sort_by(|a, b| a.1.cmp(&b.1));
-                key_value
+                Ok(key_value)
             }
         }
     };
@@ -35,12 +35,12 @@ pub fn get_select_list_from_enum(input: proc_macro::TokenStream) -> proc_macro::
     let expanded = quote! {
         #[async_trait]
         impl ActixAdminSelectListTrait for #ty {
-            async fn get_key_value(db: &DatabaseConnection) -> Vec<(String, String)> {
+            async fn get_key_value(db: &DatabaseConnection) -> Result<Vec<(String, String)>, ActixAdminError> {
                 let mut fields = Vec::new();
                 for field in #ty::iter() {
                     fields.push((field.to_string(), field.to_string()));
                 }
-                fields
+                Ok(fields)
             }
         }
     };
@@ -56,7 +56,7 @@ pub fn get_select_lists(fields: &Vec<ModelField>) -> Vec<proc_macro2::TokenStrea
         let ident_name = model_field.ident.to_string();
         let select_list_ident = Ident::new(&(model_field.select_list), Span::call_site());
         quote! {
-            #ident_name => #select_list_ident::get_key_value(db).await
+            #ident_name => #select_list_ident::get_key_value(db).await?
         }
     })
     .collect::<Vec<_>>()

src/lib.rs

@@ -122,6 +122,12 @@ use tera::{Tera, Result, to_value, try_get_value };
 use std::{ hash::BuildHasher};
 use actix_session::{Session};
 use async_trait::async_trait;
+use derive_more::{Display, Error};
+use actix_web::{
+    error,
+    http::{header::ContentType, StatusCode},
+    HttpResponse,
+};
 
 pub mod view_model;
 pub mod model;
@@ -133,7 +139,7 @@ pub mod prelude {
     pub use crate::model::{ ActixAdminModel, ActixAdminModelValidationTrait, ActixAdminModelTrait};
     pub use crate::view_model::{ ActixAdminViewModel, ActixAdminViewModelTrait, ActixAdminViewModelField, ActixAdminViewModelSerializable, ActixAdminViewModelFieldType };
     pub use actix_admin_macros::{ DeriveActixAdmin, DeriveActixAdminModel, DeriveActixAdminViewModel, DeriveActixAdminEnumSelectList, DeriveActixAdminModelSelectList };
-    pub use crate::{ ActixAdminAppDataTrait, ActixAdmin, ActixAdminConfiguration };
+    pub use crate::{ ActixAdminError, ActixAdminAppDataTrait, ActixAdmin, ActixAdminConfiguration };
     pub use crate::{ hashmap, ActixAdminSelectListTrait };
     pub use crate::routes::{ create_or_edit_post, get_admin_ctx };
     pub use crate::{ TERA };
@@ -211,7 +217,7 @@ pub trait ActixAdminAppDataTrait {
 // SelectListTrait
 #[async_trait]
 pub trait ActixAdminSelectListTrait {
-    async fn get_key_value(db: &DatabaseConnection) -> Vec<(String, String)>;
+    async fn get_key_value(db: &DatabaseConnection) -> core::result::Result<Vec<(String, String)>, ActixAdminError>;
 }
 
 
@@ -236,3 +242,75 @@ pub struct ActixAdminMenuElement {
     pub link: String,
     pub is_custom_handler: bool
 }
+
+// Errors
+#[derive(Debug, Display, Error)]
+pub enum ActixAdminError {
+    #[display(fmt = "Internal error")]
+    InternalError,
+
+    #[display(fmt = "Form has validation errors")]
+    ValidationErrors,
+
+    #[display(fmt = "Could not list entities")]
+    ListError,
+
+    #[display(fmt = "Could not create entity")]
+    CreateError,
+
+    #[display(fmt = "Could not delete entity")]
+    DeleteError,
+
+    #[display(fmt = "Could not edit entity")]
+    EditError,
+
+    #[display(fmt = "Database error")]
+    DatabaseError,
+
+    #[display(fmt = "Entity does not exist")]
+    EntityDoesNotExistError
+}
+
+
+
+impl error::ResponseError for ActixAdminError {
+    fn error_response(&self) -> HttpResponse {
+        HttpResponse::build(self.status_code())
+            .insert_header(ContentType::html())
+            .body(self.to_string())
+    }
+
+    fn status_code(&self) -> StatusCode {
+        match *self {
+            _ => StatusCode::INTERNAL_SERVER_ERROR,
+        }
+    }
+}
+
+impl std::convert::From<sea_orm::DbErr> for ActixAdminError {
+    fn from(_err: sea_orm::DbErr) -> ActixAdminError {
+        ActixAdminError::DatabaseError
+    }
+}
+
+// Notifications
+#[derive(Debug, Display, Serialize)]
+pub enum ActixAdminNotificationType {
+    #[display(fmt = "is-danger")]
+    Danger,
+}
+
+#[derive(Debug, Serialize)]
+pub struct ActixAdminNotification {
+    css_class: String,
+    message: String
+}
+
+impl std::convert::From<ActixAdminError> for ActixAdminNotification {
+    fn from(e: ActixAdminError) -> ActixAdminNotification {
+        ActixAdminNotification {
+            css_class: ActixAdminNotificationType::Danger.to_string(),
+            message: e.to_string()
+        }
+    }
+}

src/model.rs

@@ -1,4 +1,4 @@
-use crate::ActixAdminViewModelField;
+use crate::{ ActixAdminViewModelField, ActixAdminError};
 use async_trait::async_trait;
 use sea_orm::DatabaseConnection;
 use serde::Serialize;
@@ -14,7 +14,7 @@ pub trait ActixAdminModelTrait {
         page: usize,
         posts_per_page: usize,
         search: &String
-    ) -> (usize, Vec<ActixAdminModel>);
+    ) -> Result<(usize, Vec<ActixAdminModel>), ActixAdminError>;
     fn get_fields() -> Vec<ActixAdminViewModelField>;
     fn validate_model(model: &mut ActixAdminModel);
 }

src/routes/create_or_edit_get.rs

@@ -1,6 +1,8 @@
 use actix_web::{error, web, Error, HttpRequest, HttpResponse};
 use tera::{Context};
 use actix_session::{Session};
+use crate::ActixAdminError;
+use crate::ActixAdminNotification;
 use crate::prelude::*;
 
 use crate::TERA;
@@ -16,7 +18,7 @@ pub async fn create_get<T: ActixAdminAppDataTrait, E: ActixAdminViewModelTrait>(
     let db = &data.get_db();
     let model = ActixAdminModel::create_empty();
     
-    create_or_edit_get::<T, E>(&session, &data, db, model).await
+    create_or_edit_get::<T, E>(&session, &data, db, Ok(model)).await
 }
 
 pub async fn edit_get<T: ActixAdminAppDataTrait, E: ActixAdminViewModelTrait>(
@@ -32,13 +34,14 @@ pub async fn edit_get<T: ActixAdminAppDataTrait, E: ActixAdminViewModelTrait>(
     create_or_edit_get::<T, E>(&session, &data, db, model).await
 }
 
-async fn create_or_edit_get<T: ActixAdminAppDataTrait, E: ActixAdminViewModelTrait>(session: &Session, data: &web::Data<T>, db: &sea_orm::DatabaseConnection, model: ActixAdminModel) -> Result<HttpResponse, Error>{
+async fn create_or_edit_get<T: ActixAdminAppDataTrait, E: ActixAdminViewModelTrait>(session: &Session, data: &web::Data<T>, db: &sea_orm::DatabaseConnection, model_result: Result<ActixAdminModel, ActixAdminError>) -> Result<HttpResponse, Error>{
     let actix_admin = &data.get_actix_admin();
     let mut ctx = Context::new();
     add_auth_context(&session, actix_admin, &mut ctx);
     let entity_names = &actix_admin.entity_names;
     ctx.insert("entity_names", entity_names);
     let entity_name = E::get_entity_name();
+    let mut errors: Vec<crate::ActixAdminError> = Vec::new();
 
     let view_model = actix_admin.view_models.get(&entity_name).unwrap();
 
@@ -46,13 +49,33 @@ async fn create_or_edit_get<T: ActixAdminAppDataTrait, E: ActixAdminViewModelTra
         return render_unauthorized(&ctx);
     }
 
+    let model;
+    match model_result {
+        Ok(res) => {
+            model = res;
+        },
+        Err(e) => {
+            errors.push(e);
+            model = ActixAdminModel::create_empty();
+        }
+    }
+
+    let mut http_response_code = match errors.is_empty() {
+        true => HttpResponse::Ok(),
+        false => HttpResponse::InternalServerError(),
+    };    
+    let notifications: Vec<ActixAdminNotification> = errors.into_iter()
+        .map(|err| ActixAdminNotification::from(err))
+        .collect();
+
     ctx.insert("view_model", &ActixAdminViewModelSerializable::from(view_model.clone()));
-    ctx.insert("select_lists", &E::get_select_lists(db).await);
+    ctx.insert("select_lists", &E::get_select_lists(db).await?);
     ctx.insert("list_link", &E::get_list_link(&entity_name));
     ctx.insert("model", &model);
+    ctx.insert("notifications", &notifications);
     
     let body = TERA
         .render("create_or_edit.html", &ctx)
         .map_err(|err| error::ErrorInternalServerError(err))?;
-    Ok(HttpResponse::Ok().content_type("text/html").body(body))
+    Ok(http_response_code.content_type("text/html").body(body))
 }

src/routes/create_or_edit_post.rs

@@ -1,6 +1,9 @@
 use super::{render_unauthorized, user_can_access_page};
+use crate::ActixAdminError;
+use crate::ActixAdminNotification;
 use crate::prelude::*;
 use crate::TERA;
+use actix_multipart::MultipartError;
 use actix_session::Session;
 use actix_web::http::header;
 use actix_web::{error, web, Error, HttpResponse};
@@ -13,7 +16,7 @@ pub async fn create_post<T: ActixAdminAppDataTrait, E: ActixAdminViewModelTrait>
     data: web::Data<T>,
     payload: Multipart,
 ) -> Result<HttpResponse, Error> {
-    let model = ActixAdminModel::create_from_payload(payload).await.unwrap();
+    let model = ActixAdminModel::create_from_payload(payload).await;
     create_or_edit_post::<T, E>(&session, &data, model, None).await
 }
 
@@ -23,20 +26,21 @@ pub async fn edit_post<T: ActixAdminAppDataTrait, E: ActixAdminViewModelTrait>(
     payload: Multipart,
     id: web::Path<i32>,
 ) -> Result<HttpResponse, Error> {
-    let model = ActixAdminModel::create_from_payload(payload).await.unwrap();
+    let model = ActixAdminModel::create_from_payload(payload).await;
     create_or_edit_post::<T, E>(&session, &data, model, Some(id.into_inner())).await
 }
 
 pub async fn create_or_edit_post<T: ActixAdminAppDataTrait, E: ActixAdminViewModelTrait>(
     session: &Session,
     data: &web::Data<T>,
-    mut model: ActixAdminModel,
+    model_res: Result<ActixAdminModel, MultipartError>,
     id: Option<i32>,
 ) -> Result<HttpResponse, Error> {
     let actix_admin = data.get_actix_admin();
     let entity_name = E::get_entity_name();
 
     let view_model = actix_admin.view_models.get(&entity_name).unwrap();
+    let mut errors: Vec<ActixAdminError> = Vec::new();
 
     if !user_can_access_page(&session, actix_admin, view_model) {
         let mut ctx = Context::new();
@@ -44,36 +48,56 @@ pub async fn create_or_edit_post<T: ActixAdminAppDataTrait, E: ActixAdminViewMod
         return render_unauthorized(&ctx);
     }
     let db = &data.get_db();
+
+    let mut model = model_res.unwrap();
     E::validate_entity(&mut model);
 
     if model.has_errors() {
-        let mut ctx = Context::new();
+        errors.push(ActixAdminError::ValidationErrors);
-        ctx.insert("entity_names", &actix_admin.entity_names);
+        render_form::<E>(actix_admin, view_model, db, entity_name, &model, errors).await
-        ctx.insert(
-            "view_model",
-            &ActixAdminViewModelSerializable::from(view_model.clone()),
-        );
-        ctx.insert("select_lists", &E::get_select_lists(db).await);
-        ctx.insert("list_link", &E::get_list_link(&entity_name));
-        ctx.insert("model", &model);
-
-        let body = TERA
-            .render("create_or_edit.html", &ctx)
-            .map_err(|err| error::ErrorInternalServerError(err))?;
-        Ok(HttpResponse::Ok().content_type("text/html").body(body))
     } else {
-        match id {
+        let res = match id {
-            Some(id) => E::edit_entity(db, id, model).await,
+            Some(id) => E::edit_entity(db, id, model.clone()).await,
-            None => E::create_entity(db, model).await,
+            None => E::create_entity(db, model.clone()).await,
         };
 
+        match res {
+            Ok(_) => {
                 Ok(HttpResponse::SeeOther()
                 .append_header((
                     header::LOCATION,
                     format!("/admin/{}/list", view_model.entity_name),
                 ))
                 .finish())
+            },
+            Err(e) => {
+                errors.push(e);
+                render_form::<E>(actix_admin, view_model, db, entity_name, &model, errors).await
             } 
+        }    
+    }
+}
+
+async fn render_form<E: ActixAdminViewModelTrait>(actix_admin: &ActixAdmin, view_model: &ActixAdminViewModel, db: &&sea_orm::DatabaseConnection, entity_name: String, model: &ActixAdminModel, errors: Vec<ActixAdminError>) -> Result<HttpResponse, Error> {
+    let mut ctx = Context::new();
+    ctx.insert("entity_names", &actix_admin.entity_names);
+    ctx.insert(
+        "view_model",
+        &ActixAdminViewModelSerializable::from(view_model.clone()),
+    );
+    ctx.insert("select_lists", &E::get_select_lists(db).await?);
+    ctx.insert("list_link", &E::get_list_link(&entity_name));
+    ctx.insert("model", model);
+    
+    let notifications: Vec<ActixAdminNotification> = errors.into_iter()
+        .map(|err| ActixAdminNotification::from(err))
+        .collect();
+    
+    ctx.insert("notifications", &notifications);
+    let body = TERA
+        .render("create_or_edit.html", &ctx)
+        .map_err(|err| error::ErrorInternalServerError(err))?;
+    Ok(HttpResponse::Ok().content_type("text/html").body(body))
 }
 
 #[doc(hidden)]

src/routes/delete.rs

@@ -24,10 +24,12 @@ pub async fn delete<T: ActixAdminAppDataTrait, E: ActixAdminViewModelTrait>(
     }
 
     let db = &data.get_db();
-    let _result = E::delete_entity(db, id.into_inner()).await;
+    let result = E::delete_entity(db, id.into_inner()).await;
 
-    Ok(HttpResponse::Ok()
+    match result {
-        .finish())
+        Ok(_) => Ok(HttpResponse::Ok().finish()),
+        Err(_) => Ok(HttpResponse::InternalServerError().finish())
+    }   
 }
 
 pub async fn delete_many<T: ActixAdminAppDataTrait, E: ActixAdminViewModelTrait>(
@@ -40,6 +42,7 @@ pub async fn delete_many<T: ActixAdminAppDataTrait, E: ActixAdminViewModelTrait>
     let entity_name = E::get_entity_name();
 
     let view_model = actix_admin.view_models.get(&entity_name).unwrap();
+    let mut errors: Vec<crate::ActixAdminError> = Vec::new();
 
     if !user_can_access_page(&session, actix_admin, view_model) {
         let mut ctx = Context::new();
@@ -57,13 +60,24 @@ pub async fn delete_many<T: ActixAdminAppDataTrait, E: ActixAdminViewModelTrait>
     
     // TODO: implement delete_many
     for id in entity_ids {
-        let _result = E::delete_entity(db, id).await;
+        let result = E::delete_entity(db, id).await;
+        match result {
+            Err(e) => errors.push(e),
+            _ => {}
+        }
     }
 
+    match errors.is_empty() {
+        true => {
             Ok(HttpResponse::SeeOther()
             .append_header((
                 header::LOCATION,
                 format!("/admin/{}/list?render_partial=true", entity_name),
             ))
             .finish())
+        },
+        false => {
+            Ok(HttpResponse::InternalServerError().finish())
+        }
+    }
 }

src/routes/index.rs

@@ -21,9 +21,11 @@ pub fn get_admin_ctx<T: ActixAdminAppDataTrait>(session: Session, data: &web::Da
 
 pub async fn index<T: ActixAdminAppDataTrait>(session: Session, data: web::Data<T>) -> Result<HttpResponse, Error> {
     let actix_admin = data.get_actix_admin();
+    let notifications: Vec<crate::ActixAdminNotification> = Vec::new();
 
     let mut ctx = Context::new();
     ctx.insert("entity_names", &actix_admin.entity_names);
+    ctx.insert("notifications", &notifications);    
 
     add_auth_context(&session, actix_admin, &mut ctx);
 

src/routes/list.rs

@@ -6,6 +6,7 @@ use crate::prelude::*;
 use crate::ActixAdminViewModelTrait;
 use crate::ActixAdminViewModel;
 use crate::ActixAdminModel;
+use crate::ActixAdminNotification;
 use crate::TERA;
 use actix_session::{Session};
 use super::{ add_auth_context, user_can_access_page, render_unauthorized};
@@ -28,6 +29,7 @@ pub async fn list<T: ActixAdminAppDataTrait, E: ActixAdminViewModelTrait>(
     let actix_admin = data.get_actix_admin();
     let entity_name = E::get_entity_name();
     let view_model: &ActixAdminViewModel = actix_admin.view_models.get(&entity_name).unwrap();
+    let mut errors: Vec<ActixAdminError> = Vec::new();
     
     let mut ctx = Context::new();
     add_auth_context(&session, actix_admin, &mut ctx);
@@ -48,22 +50,40 @@ pub async fn list<T: ActixAdminAppDataTrait, E: ActixAdminViewModelTrait>(
     let search = params.search.clone().unwrap_or(String::new());
 
     let db = data.get_db();
-    let result: (usize, Vec<ActixAdminModel>) = E::list(db, page, entities_per_page, &search).await;
+    let result = E::list(db, page, entities_per_page, &search).await;
-    let entities = result.1;
+    match result {
-    let num_pages = result.0;
+        Ok(res) => {
+            let entities = res.1;
+            let num_pages = res.0;
+            ctx.insert("entities", &entities);
+            ctx.insert("num_pages", &num_pages);
+        },
+        Err(e) => {
+            ctx.insert("entities", &Vec::<ActixAdminModel>::new());
+            ctx.insert("num_pages", &0);
+            errors.push(e);
+        }
+    }
+
+    let mut http_response_code = match errors.is_empty() {
+        false => HttpResponse::InternalServerError(),
+        true => HttpResponse::Ok()
+    };    
+    let notifications: Vec<ActixAdminNotification> = errors.into_iter()
+        .map(|err| ActixAdminNotification::from(err))
+        .collect();
 
     ctx.insert("entity_name", &entity_name);
-    ctx.insert("entities", &entities);
+    ctx.insert("notifications", &notifications);
     ctx.insert("page", &page);
     ctx.insert("params", &entities_per_page);
     ctx.insert("entities_per_page", &entities_per_page);
     ctx.insert("render_partial", &render_partial);
-    ctx.insert("num_pages", &num_pages);
     ctx.insert("view_model", &ActixAdminViewModelSerializable::from(view_model.clone()));
     ctx.insert("search", &search);
 
     let body = TERA
         .render("list.html", &ctx)
         .map_err(|err| error::ErrorInternalServerError(err))?;
-    Ok(HttpResponse::Ok().content_type("text/html").body(body))
+    Ok(http_response_code.content_type("text/html").body(body))
 }

src/routes/show.rs

@@ -2,6 +2,7 @@ use actix_web::{error, web, Error, HttpResponse};
 use actix_session::{Session};
 use tera::{Context};
 
+use crate::ActixAdminNotification;
 use crate::prelude::*;
 
 use crate::TERA;
@@ -11,20 +12,43 @@ use super::{ add_auth_context };
 pub async fn show<T: ActixAdminAppDataTrait, E: ActixAdminViewModelTrait>(session: Session, data: web::Data<T>, id: web::Path<i32>) -> Result<HttpResponse, Error> {
     let actix_admin = data.get_actix_admin();
     let db = &data.get_db();
-    let model = E::get_entity(db, id.into_inner()).await;
+    let result = E::get_entity(db, id.into_inner()).await;
+    let mut errors: Vec<crate::ActixAdminError> = Vec::new();
+
+    let model;
+    
+    match result {
+        Ok(res) => {
+            model = res;
+        },
+        Err(e) => {
+            errors.push(e);
+            model = ActixAdminModel::create_empty();
+        }
+    }
+
     let entity_name = E::get_entity_name();
     let view_model: &ActixAdminViewModel = actix_admin.view_models.get(&entity_name).unwrap();
 
+    let mut http_response_code = match errors.is_empty() {
+        false => HttpResponse::InternalServerError(),
+        true => HttpResponse::Ok()
+    };    
+    let notifications: Vec<ActixAdminNotification> = errors.into_iter()
+        .map(|err| ActixAdminNotification::from(err))
+        .collect();
+
     let mut ctx = Context::new();
     ctx.insert("model", &model);
     ctx.insert("view_model", &ActixAdminViewModelSerializable::from(view_model.clone()));
     ctx.insert("list_link", &E::get_list_link(&entity_name));
     ctx.insert("entity_names", &actix_admin.entity_names);
+    ctx.insert("notifications", &notifications);
 
     add_auth_context(&session, actix_admin, &mut ctx);
 
     let body = TERA
         .render("show.html", &ctx)
         .map_err(|_| error::ErrorInternalServerError("Template error"))?;
-    Ok(HttpResponse::Ok().content_type("text/html").body(body))
+    Ok(http_response_code.content_type("text/html").body(body))
 }

src/view_model.rs

@@ -5,6 +5,7 @@ use std::collections::HashMap;
 use crate::ActixAdminModel;
 use actix_session::{Session};
 use std::convert::From;
+use crate::ActixAdminError;
 
 #[async_trait(?Send)]
 pub trait ActixAdminViewModelTrait {
@@ -13,14 +14,14 @@ pub trait ActixAdminViewModelTrait {
         page: usize,
         entities_per_page: usize,
         search: &String
-    ) -> (usize, Vec<ActixAdminModel>);
+    ) -> Result<(usize, Vec<ActixAdminModel>), ActixAdminError>;
     
     // TODO: Replace return value with proper Result Type containing Ok or Err
-    async fn create_entity(db: &DatabaseConnection, model: ActixAdminModel) -> ActixAdminModel;
+    async fn create_entity(db: &DatabaseConnection, model: ActixAdminModel) -> Result<ActixAdminModel, ActixAdminError>;
-    async fn delete_entity(db: &DatabaseConnection, id: i32) -> bool;
+    async fn delete_entity(db: &DatabaseConnection, id: i32) -> Result<bool, ActixAdminError>;
-    async fn get_entity(db: &DatabaseConnection, id: i32) -> ActixAdminModel;
+    async fn get_entity(db: &DatabaseConnection, id: i32) -> Result<ActixAdminModel, ActixAdminError>;
-    async fn edit_entity(db: &DatabaseConnection, id: i32, model: ActixAdminModel) -> ActixAdminModel;
+    async fn edit_entity(db: &DatabaseConnection, id: i32, model: ActixAdminModel) -> Result<ActixAdminModel, ActixAdminError>;
-    async fn get_select_lists(db: &DatabaseConnection) -> HashMap<String, Vec<(String, String)>>;
+    async fn get_select_lists(db: &DatabaseConnection) -> Result<HashMap<String, Vec<(String, String)>>, ActixAdminError>;
     fn validate_entity(model: &mut ActixAdminModel);
 
     fn get_entity_name() -> String;

templates/base.html

@@ -17,6 +17,16 @@
     </div>
     {% include "navbar.html" %}
     <div class="container is-fluid">
+        <div id="notifications">
+            {% if notifications %}
+            {% for notification in notifications -%}
+                <div class="notification mb-4 is-light {{ notification.css_class }}">
+                    <button class="delete" onclick="this.parentElement.remove()"></button>
+                {{ notification.message }}
+            </div>
+            {% endfor %}
+            {% endif %}
+        </div>
         {% block content %}
         {% endblock content %}
     </div>

templates/create_or_edit.html

@@ -1,7 +1,7 @@
 {% extends "base.html" %}
 
 {% block content %}
-<form hx-boost="true" hx-indicator="#loading" hx-encoding="multipart/form-data" method="post" enctype="multipart/form-data">
+<form hx-boost="true" hx-indicator="#loading" hx-push-url="true" hx-encoding="multipart/form-data" method="post" enctype="multipart/form-data">
     {% for model_field in view_model.fields -%}
     <div class="field">
         <label class="{{ model_field | get_html_input_type }}" for="{{ model_field.field_name }}">

templates/head.html

@@ -36,8 +36,13 @@
 
             });
         });
-
     });
+
+    htmx.on("htmx:responseError", function () {
+        document.getElementById("notifications").insertAdjacentHTML(
+            "afterend",
+                "<div class=\"notification mb-4 is-light is-danger\"><button class=\"delete\" onclick=\"this.parentElement.remove()\"></button>An Error occurred</div>");
+    })
 </script>
 
 <style>
@@ -51,7 +56,7 @@
         background: rgba(255, 255, 255, 0.3);
         justify-content: center;
         align-items: center;
-        z-index: 5;
+        z-index: 6;
         pointer-events: none
     }
 </style>

templates/list.html

@@ -6,7 +6,7 @@
 <div class="columns">
     <div class="column">
         <div class="buttons">
-            <a class="button is-primary" href="create">Create</a>
+            <a class="button is-primary" href="create" hx-boost="true" hx-indicator="#loading">Create</a>
 
             <div hx-include="#checked-rows" hx-target="#{{ entity_name }}table" class="dropdown is-hoverable">
                 <div class="dropdown-trigger">
@@ -20,7 +20,7 @@
                 <div class="dropdown-menu" id="dropdown-menu4">
                     <div class="dropdown-content">
                         <div class="dropdown-item">
-                            <a href="#" hx-confirm="Are you sure?" hx-delete="delete">Delete</a>
+                            <a href="#" hx-indicator="#loading" hx-confirm="Are you sure?" hx-delete="delete">Delete</a>
                         </div>
                     </div>
                 </div>
@@ -45,7 +45,7 @@
     </div>
     <div class="column is-narrow">
         <div>
-            <form>
+            <form hx-boost="true" hx-indicator="#loading">
                 <input type="hidden" value="{{ search }}" name="search">
                 <div class="select">
                     <div class="control has-icons-left has-icons-right">
@@ -82,7 +82,7 @@
                     </th>
                 </tr>
             </thead>
-            <tbody hx-confirm="Are you sure?" hx-target="closest tr" hx-swap="outerHTML">
+            <tbody hx-confirm="Are you sure?" hx-target="closest tr" hx-indicator="#loading" hx-swap="outerHTML">
                 {% for entity in entities -%}
                 <tr>
                     <td><input type="checkbox" name="ids" value="{{ entity.primary_key }}"></td>

templates/navbar.html

@@ -17,9 +17,9 @@
         {% if category == "" %}
           {% for menu_element in entities %}
             {% if menu_element.is_custom_handler %}
-            <a href="/admin/{{ menu_element.link }}" class="navbar-item {% if entity_name and entity_name == menu_element.name %}is-active{% endif %}">{{ menu_element.name }}</a>
+            <a href="/admin/{{ menu_element.link }}" hx-boost="true" hx-indicator="#loading" class="navbar-item {% if entity_name and entity_name == menu_element.name %}is-active{% endif %}">{{ menu_element.name }}</a>
             {% else %}
-            <a href="/admin/{{ menu_element.link }}/list" class="navbar-item {% if entity_name and entity_name == menu_element.name %}is-active{% endif %}">{{ menu_element.name | title }}</a>
+            <a href="/admin/{{ menu_element.link }}/list" hx-boost="true" hx-indicator="#loading" class="navbar-item {% if entity_name and entity_name == menu_element.name %}is-active{% endif %}">{{ menu_element.name | title }}</a>
             {% endif %}
           {%- endfor %}
         {% else %}
@@ -30,9 +30,9 @@
             <div class="navbar-dropdown">
           {% for menu_element in entities %}
             {% if menu_element.is_custom_handler %}
-            <a href="/admin/{{ menu_element.link }}" class="navbar-item {% if entity_name and entity_name == menu_element.name %}is-active{% endif %}">{{ menu_element.name }}</a>
+            <a href="/admin/{{ menu_element.link }}" hx-boost="true" hx-indicator="#loading" class="navbar-item {% if entity_name and entity_name == menu_element.name %}is-active{% endif %}">{{ menu_element.name }}</a>
             {% else %}
-            <a href="/admin/{{ menu_element.link }}/list" class="navbar-item {% if entity_name and entity_name == menu_element.name %}is-active{% endif %}">{{ menu_element.name | title }}</a>
+            <a href="/admin/{{ menu_element.link }}/list" hx-boost="true" hx-indicator="#loading" class="navbar-item {% if entity_name and entity_name == menu_element.name %}is-active{% endif %}">{{ menu_element.name | title }}</a>
             {% endif %}
           {%- endfor %}
             </div>
@@ -46,11 +46,11 @@
         <div class="buttons">
           {% if enable_auth %}
           {% if user_is_logged_in %}
-          <a href="{{ logout_link }}" class="button is-light">
+          <a href="{{ logout_link }}" hx-boost="true" hx-indicator="#loading" class="button is-light">
             Log out
           </a>
           {% else %}
-          <a href="{{ login_link }}" class="button is-light">
+          <a href="{{ login_link }}" hx-boost="true" hx-indicator="#loading" class="button is-light">
             Log in
           </a>
           {% endif %}

tests/test_setup/helper.rs

@@ -79,7 +79,7 @@ async fn create_post_from_plaintext<
     text: String,
 ) -> Result<HttpResponse, Error> {
     let model = ActixAdminModel::from(text);
-    create_or_edit_post::<T, E>(&session, &data, model, None).await
+    create_or_edit_post::<T, E>(&session, &data, Ok(model), None).await
 }
 
 async fn edit_post_from_plaintext<
@@ -92,5 +92,5 @@ async fn edit_post_from_plaintext<
     id: web::Path<i32>,
 ) -> Result<HttpResponse, Error> {
     let model = ActixAdminModel::from(text);
-    create_or_edit_post::<T, E>(&session, &data, model, Some(id.into_inner())).await
+    create_or_edit_post::<T, E>(&session, &data, Ok(model), Some(id.into_inner())).await
 }