add partials

README.md

@@ -95,3 +95,14 @@ impl Validate for MyStruct {
     }
 }
 ```
+
+### Partials
+Sometimes you need only some fields of your `Model`. When deriving the `Model` trait you automatically get a `Partial` of your model. Partials are only meant for reading values so you cant call functions like `update()`, but you can still get a `Reference` to the original `Model`. This saves bandwidth and memory. You can access it like this:
+
+```rust
+// say you are only interested in the reference field `other` of `MyStruct`
+let ms = MyStruct::get_partial("someid", &serde_json::json!({"other": 1})).await.unwrap();
+
+let myref = ms.other.unwrap(); // will be there
+let name = ms.name.unwrap() // will panic!
+```

mongod_derive/src/lib.rs

@@ -42,6 +42,8 @@ pub fn model_derive(input: TokenStream) -> TokenStream {
     let input = parse_macro_input!(input as DeriveInput);
 
     let name = input.ident;
+    let name_str = name.to_string().to_snake();
+    let partial_name = syn::Ident::new(&format!("Partial{}", name), name.span());
 
     // Generate code for each field
     let field_code = if let Data::Struct(data_struct) = input.data {
@@ -91,8 +93,36 @@ pub fn model_derive(input: TokenStream) -> TokenStream {
                     }
                 }).collect();
 
+                let partial_struct: Vec<_> = fields_named
+                    .named
+                    .iter()
+                    .map(|field| {
+                        let field_name = &field.ident.as_ref().unwrap();
+                        let field_type = &field.ty;
+                        let field_name_str = field_name.to_string();
+
+                        if field_name_str == "_id" {
+                            return quote! {
+                                pub _id: String,
+                            };
+                        }
+
+                        if is_type(field_type, "Option") {
+                            return quote! {
+                                pub #field_name: #field_type,
+                            };
+                        }
+
+                        quote! {
+                            pub #field_name: Option<#field_type>,
+                        }
+                    })
+                    .collect();
+
                 quote! {
                     impl mongod::model::Model for #name {
+                        type Partial = #partial_name;
+
                         async fn update_values(
                             &mut self,
                             obj: &serde_json::Map<String, serde_json::Value>,
@@ -101,6 +131,21 @@ pub fn model_derive(input: TokenStream) -> TokenStream {
                             #( #field_process_code )*
                         }
                     }
+
+                    #[derive(Debug, Clone, serde::Serialize, serde::Deserialize)]
+                    pub struct #partial_name {
+                        #( #partial_struct )*
+                    }
+
+                    impl mongod::model::reference::Referencable for #partial_name {
+                        fn collection_name() -> &'static str {
+                            #name_str
+                        }
+
+                        fn id(&self) -> &str {
+                            &self._id
+                        }
+                    }
                 }
             }
             _ => unimplemented!(),

src/model/mod.rs

@@ -1,5 +1,9 @@
-use mongodb::results::{DeleteResult, InsertOneResult};
+use mongodb::{
+    options::{FindOneOptions, FindOptions},
+    results::{DeleteResult, InsertOneResult},
+};
 use reference::Referencable;
+use serde::de::DeserializeOwned;
 use serde_json::{Map, Value};
 use valid::Validate;
 
@@ -26,6 +30,8 @@ pub enum UpdateError {
 pub trait Model:
     Sized + Referencable + Validate + serde::Serialize + for<'a> serde::Deserialize<'a>
 {
+    type Partial: DeserializeOwned;
+
     /// Insert the `Model` into the database
     fn insert(
         &self,
@@ -77,8 +83,56 @@ pub trait Model:
         }
     }
 
+    /// Get a partial `Model` by id from the database with only some fields retrieved.
+    #[must_use]
+    fn get_partial(
+        id: &str,
+        part: &serde_json::Value,
+    ) -> impl std::future::Future<Output = Option<Self::Partial>> {
+        async move {
+            let db = get_mongo!();
+            let collection = col!(db, Self::collection_name());
+            let doc = collection
+                .find_one(
+                    id_of!(id),
+                    Some(
+                        FindOneOptions::builder()
+                            .projection(Some(mongodb::bson::to_document(part).unwrap()))
+                            .build(),
+                    ),
+                )
+                .await
+                .ok()??;
+            mongodb::bson::from_document(doc).ok()
+        }
+    }
+
     /// Get a `Model` by using a filter from the database
     #[must_use]
+    fn find_one_partial(
+        filter: mongodb::bson::Document,
+        part: &serde_json::Value,
+    ) -> impl std::future::Future<Output = Option<Self::Partial>> {
+        async move {
+            let db = get_mongo!();
+            let collection = col!(db, Self::collection_name());
+            let doc = collection
+                .find_one(
+                    filter,
+                    Some(
+                        FindOneOptions::builder()
+                            .projection(Some(mongodb::bson::to_document(part).unwrap()))
+                            .build(),
+                    ),
+                )
+                .await
+                .ok()??;
+            mongodb::bson::from_document(doc).ok()
+        }
+    }
+
+    /// Get a partial `Model` by using a filter from the database
+    #[must_use]
     fn find_one(
         filter: mongodb::bson::Document,
     ) -> impl std::future::Future<Output = Option<Self>> {
@@ -106,6 +160,33 @@ pub trait Model:
         }
     }
 
+    /// Get multiple partial `Model`s by using a filter from the database
+    #[must_use]
+    fn find_partial(
+        filter: mongodb::bson::Document,
+        part: &serde_json::Value,
+    ) -> impl std::future::Future<Output = Option<Vec<Self>>> {
+        async move {
+            let db = get_mongo!();
+            let collection = col!(db, Self::collection_name());
+            let mut results = collection
+                .find(
+                    filter,
+                    Some(
+                        FindOptions::builder()
+                            .projection(Some(mongodb::bson::to_document(part).unwrap()))
+                            .build(),
+                    ),
+                )
+                .await
+                .ok()?;
+            let docs = collect_results!(results);
+            docs.into_iter()
+                .map(|x| mongodb::bson::from_document(x).unwrap())
+                .collect()
+        }
+    }
+
     /// Update values of `Model` into database
     fn update(
         &mut self,