Features/parent improvements (#23)

* parent instr refactoring in process * parent improvements progress * Parent child field progress * parent improvements in progress * moderate refactoring * parent improvements in progress * Parent improvements in progress * Small refactoring * Parent improvements progress * fix readme * children instr renamed to child_parents
Artem-Romanenia · Nov 27, 2024 · d79c260 · d79c260
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diff --git a/Cargo.toml b/Cargo.toml
@@ -3,7 +3,7 @@ name = "o2o"
 version = "0.4.11"
 edition = "2021"
 authors = ["Artem Romanenia <artem.romanenia@gmail.com>"]
-categories = ["rust-patterns"]
+categories = ["rust-patterns", "no-std", "development-tools"]
 description = "Object to Object mapper for Rust. Derive '(Try)From' and '(Try)Into' traits."
 keywords = ["from", "into", "copy", "mapper", "derive"]
 license = "MIT OR Apache-2.0"

diff --git a/README.md b/README.md
@@ -18,7 +18,7 @@ impl From<Person> for PersonDto {
 }
 ```
 
-Writing code like above is not the most exciting or emotionally rewarding part of working with Rust. If you're Ok with letting procedural macro write it for you, welcome to the rest of this page.
+Writing code like above is not the most exciting or rewarding part of working with Rust. If you're Ok with letting procedural macro write it for you, welcome to the rest of this page.
 
 ## Basic Example<!-- omit from toc --> 
 
@@ -94,7 +94,7 @@ And here's the code that `o2o` generates (from here on, generated code is produc
   }
   impl ::core::convert::TryInto<Person> for PersonDto {
       type Error = std::io::Error;
-      fn try_into(self) -> Result<Person, std::io::Error> {
+      fn try_into(self) -> ::core::result::Result<Person, std::io::Error> {
           Ok(Person {
               id: self.id,
               name: self.name,
@@ -118,6 +118,7 @@ And here's the code that `o2o` generates (from here on, generated code is produc
 
 ## Some milestones<!-- omit from toc --> 
 
+* **v0.5.0** Refactoring and improved support for 'flattened' child fields: `#[child()]`, `#[child_parents()]` and `#[parent()]` instructions
 * **v0.4.9** Support for `#![no_std]`
 * **v0.4.4** Fallible conversions
 * **v0.4.3** Enum-to-primitive type conversions with `#[literal(...)]` and `#[pattern(...)]`
@@ -144,6 +145,8 @@ And here's the code that `o2o` generates (from here on, generated code is produc
   - [Item attributes (attributes for `#[] impl`, `#[] fn`, `fn() { #![] }`)](#item-attributes-attributes-for--impl--fn-fn---)
   - [Slightly complex example](#slightly-complex-example)
   - [Flatened children](#flatened-children)
+    - [Child instructions](#child-instructions)
+    - [Parent instructions](#parent-instructions)
   - [Tuple structs](#tuple-structs)
   - [Tuples](#tuples)
   - [Type hints](#type-hints)
@@ -499,7 +502,7 @@ struct EntityDto {
   }
   impl ::core::convert::TryInto<Entity> for EntityDto {
       type Error = std::num::ParseIntError;
-      fn try_into(self) -> Result<Entity, std::num::ParseIntError> {
+      fn try_into(self) -> ::core::result::Result<Entity, std::num::ParseIntError> {
           Ok(Entity {
               some_int: self.some_int,
               str: self.str,
@@ -509,7 +512,7 @@ struct EntityDto {
   }
   impl ::core::convert::TryInto<Entity> for &EntityDto {
       type Error = std::num::ParseIntError;
-      fn try_into(self) -> Result<Entity, std::num::ParseIntError> {
+      fn try_into(self) -> ::core::result::Result<Entity, std::num::ParseIntError> {
           Ok(Entity {
               some_int: self.some_int,
               str: self.str.clone(),
@@ -849,7 +852,7 @@ struct Wrapper(#[from(@.parse::<i32>()?)]i32);
   ``` rust ignore
   impl ::core::convert::TryFrom<String> for Wrapper {
       type Error = std::num::ParseIntError;
-      fn try_from(value: String) -> Result<Wrapper, std::num::ParseIntError> {
+      fn try_from(value: String) -> ::core::result::Result<Wrapper, std::num::ParseIntError> {
           Ok(Wrapper(value.parse::<i32>()?))
       }
   }
@@ -1129,7 +1132,9 @@ impl EmployeeDto {
 
 ### Flatened children
 
-When the instructions are put on the side that contains flatened properties, conversion `From<T>` and `IntoExisting<T>` only requires usage of a member level `#[child(...)]` instruction, which accepts a path to the unflatened field (*without* the field name itself).
+#### Child instructions
+
+When the instructions are put on the side that contains flatened (child) properties, conversions `From<T>` and `IntoExisting<T>` only require usage of a member level `#[child(...)]` instruction, which accepts a dot separated path to the parent field (*without* the field name itself).
 ``` rust
 use o2o::o2o;
 
@@ -1188,7 +1193,7 @@ struct CarDto {
   ```
 </details>
 
-When you need an `Into<T>` conversion, **o2o** also expects you to provide types for flatened properties via struct level `#[children(...)]` instruction:
+When you need an `Into<T>` conversion, **o2o** also expects you to provide types for parent properties via struct level `#[child_parents(...)]` instruction:
 
 ``` rust
 use o2o::o2o;
@@ -1208,7 +1213,7 @@ struct Machine {
 
 #[derive(o2o)]
 #[owned_into(Car)]
-#[children(vehicle: Vehicle, vehicle.machine: Machine)]
+#[child_parents(vehicle: Vehicle, vehicle.machine: Machine)]
 struct CarDto {
     number_of_doors: i8,
 
@@ -1243,36 +1248,29 @@ struct CarDto {
   ```
 </details>
 
-The reverse case, where you have to put **o2o** insturctions on the side that has field that are being flatened, is slightly tricky:
+#### Parent instructions
 
-``` rust
-use o2o::o2o;
-use o2o::traits::IntoExisting;
+When the instructions are put on the side that contains parent property that is being flatened, conversions `Into<T>` and `IntoExisting<T>` can be done by using #[parent(...)] instruction and listing child properties:
 
-#[derive(o2o)]
+``` rust
+#[derive(o2o::o2o)]
 #[owned_into(CarDto)]
 struct Car {
     number_of_doors: i8,
-    #[parent]
+    #[parent(number_of_seats, [parent(brand, year)] machine)] // [parent] instruction can be recursive
     vehicle: Vehicle
 }
 
-#[derive(o2o)]
-#[owned_into_existing(CarDto)]
 struct Vehicle {
     number_of_seats: i16,
-    #[parent]
     machine: Machine,
 }
 
-#[derive(o2o)]
-#[owned_into_existing(CarDto)]
 struct Machine {
     brand: String,
     year: i16
 }
 
-// CarDto has to implement `Default` trait in this case.
 #[derive(Default)]
 struct CarDto {
     number_of_doors: i8,
@@ -1287,22 +1285,59 @@ struct CarDto {
   ``` rust ignore
   impl ::core::convert::Into<CarDto> for Car {
       fn into(self) -> CarDto {
-          let mut obj: CarDto = Default::default();
-          obj.number_of_doors = self.number_of_doors;
-          self.vehicle.into_existing(&mut obj);
-          obj
-      }
-  }
-  impl o2o::traits::IntoExisting<CarDto> for Vehicle {
-      fn into_existing(self, other: &mut CarDto) {
-          other.number_of_seats = self.number_of_seats;
-          self.machine.into_existing(other);
+          CarDto {
+              number_of_doors: self.number_of_doors,
+              number_of_seats: self.vehicle.number_of_seats,
+              brand: self.vehicle.machine.brand,
+              year: self.vehicle.machine.year,
+          }
       }
   }
-  impl o2o::traits::IntoExisting<CarDto> for Machine {
-      fn into_existing(self, other: &mut CarDto) {
-          other.brand = self.brand;
-          other.year = self.year;
+  ```
+</details>
+
+When you need an `From<T>` conversion, **o2o** also expects you to provide types for nested parent properties:
+
+``` rust
+#[derive(o2o::o2o)]
+#[from_owned(CarDto)]
+struct Car {
+    number_of_doors: i8,
+    #[parent(number_of_seats, [parent(brand, year)] machine: Machine)] // 'machine' needs to have type here
+    vehicle: Vehicle
+}
+
+struct Vehicle {
+    number_of_seats: i16,
+    machine: Machine,
+}
+
+struct Machine {
+    brand: String,
+    year: i16
+}
+
+#[derive(Default)]
+struct CarDto {
+    number_of_doors: i8,
+    number_of_seats: i16,
+    brand: String,
+    year: i16
+}
+```
+<details>
+  <summary>View generated code</summary>
+
+  ``` rust ignore
+  impl ::core::convert::From<CarDto> for Car {
+      fn from(value: CarDto) -> Car {
+          Car {
+              number_of_doors: value.number_of_doors,
+              vehicle: Vehicle {
+                  number_of_seats: value.number_of_seats,
+                  machine: Machine { brand: value.brand, year: value.year },
+              },
+          }
       }
   }
   ```
@@ -1799,7 +1834,7 @@ struct Machine {
 
 #[derive(o2o)]
 #[map_ref(Car)]
-#[children(vehicle: Vehicle, vehicle.machine: Machine)]
+#[child_parents(vehicle: Vehicle, vehicle.machine: Machine)]
 #[ghosts(vehicle.machine@id: {321})]
 struct CarDto {
     number_of_doors: i8,
@@ -2049,7 +2084,7 @@ enum EnumWithDataDto {
   }
   impl ::core::convert::TryInto<EnumWithData> for EnumWithDataDto {
       type Error = std::num::ParseIntError;
-      fn try_into(self) -> Result<EnumWithData, std::num::ParseIntError> {
+      fn try_into(self) -> ::core::result::Result<EnumWithData, std::num::ParseIntError> {
           Ok(match self {
               EnumWithDataDto::Item1(f0, f1) => EnumWithData::Item1(f0.parse::<i32>()?, f1),
               EnumWithDataDto::Item2 { str, i_str } => EnumWithData::Item2 {
@@ -2241,7 +2276,7 @@ enum EnumDto {
   }
   impl ::core::convert::TryInto<Enum> for EnumDto {
       type Error = String;
-      fn try_into(self) -> Result<Enum, String> {
+      fn try_into(self) -> ::core::result::Result<Enum, String> {
           Ok(match self {
               EnumDto::Var1 => Enum::Var1,
               EnumDto::Var2(f0, f1) => Enum::Var2(f0, f1),
@@ -2277,7 +2312,7 @@ enum EnumDto {
   ``` rust ignore
   impl ::core::convert::TryFrom<EnumDto> for Enum {
       type Error = String;
-      fn try_from(value: EnumDto) -> Result<Enum, String> {
+      fn try_from(value: EnumDto) -> ::core::result::Result<Enum, String> {
           Ok(match value {
               EnumDto::Var1 => Enum::Var1,
               EnumDto::Var2(f0, f1) => Enum::Var2(f0, f1),
@@ -2650,7 +2685,7 @@ enum HttpStatusFamily {
   ``` rust ignore
   impl ::core::convert::TryFrom<i32> for HttpStatus {
       type Error = StaticStr;
-      fn try_from(value: i32) -> Result<HttpStatus, StaticStr> {
+      fn try_from(value: i32) -> ::core::result::Result<HttpStatus, StaticStr> {
           Ok(match value {
               200 => HttpStatus::Ok,
               201 => HttpStatus::Created,
@@ -2664,7 +2699,7 @@ enum HttpStatusFamily {
   }
   impl ::core::convert::TryInto<i32> for HttpStatus {
       type Error = StaticStr;
-      fn try_into(self) -> Result<i32, StaticStr> {
+      fn try_into(self) -> ::core::result::Result<i32, StaticStr> {
           Ok(match self {
               HttpStatus::Ok => 200,
               HttpStatus::Created => 201,
@@ -2678,7 +2713,7 @@ enum HttpStatusFamily {
 
   impl ::core::convert::TryFrom<i32> for HttpStatusFamily {
     type Error = StaticStr;
-    fn try_from(value: i32) -> Result<HttpStatusFamily, StaticStr> {
+    fn try_from(value: i32) -> ::core::result::Result<HttpStatusFamily, StaticStr> {
         Ok(match value {
             100..=199 => HttpStatusFamily::Information,
             200..=299 => HttpStatusFamily::Success,

diff --git a/o2o-impl/src/ast.rs b/o2o-impl/src/ast.rs
@@ -1,10 +1,11 @@
 use crate::attr::{self};
 use crate::attr::{DataTypeAttrs, MemberAttrs};
 use proc_macro2::Span;
+use quote::ToTokens;
 use syn::punctuated::Punctuated;
 use syn::spanned::Spanned;
 use syn::token::Comma;
-use syn::{Attribute, DataEnum, DataStruct, DeriveInput, Fields, Generics, Ident, Index, Member, Result};
+use syn::{Attribute, DataEnum, DataStruct, DeriveInput, Fields, Generics, Ident, Index, Member, Path, Result};
 
 #[derive(Default)]
 struct Context {
@@ -41,6 +42,8 @@ pub(crate) struct Field {
     pub attrs: MemberAttrs,
     pub idx: usize,
     pub member: Member,
+    pub member_str: String,
+    pub ty: Option<Path>
 }
 
 impl<'a> Field {
@@ -70,16 +73,24 @@ impl<'a> Field {
             .collect()
     }
 
-    fn from_syn(i: usize, node: &'a syn::Field, bark: bool) -> Result<Self> {
+    fn from_syn(idx: usize, node: &'a syn::Field, bark: bool) -> Result<Self> {
+        let member = node.ident.clone().map(Member::Named).unwrap_or_else(|| {
+            Member::Unnamed(Index {
+                index: idx as u32,
+                span: node.ty.span(),
+            })
+        });
+        let member_str = member.to_token_stream().to_string();
+
         Ok(Field {
             attrs: attr::get_member_attrs(SynDataTypeMember::Field(node), bark)?,
-            idx: i,
-            member: node.ident.clone().map(Member::Named).unwrap_or_else(|| {
-                Member::Unnamed(Index {
-                    index: i as u32,
-                    span: node.ty.span(),
-                })
-            }),
+            idx,
+            member,
+            member_str,
+            ty: match &node.ty {
+                syn::Type::Path(p) => Some(p.path.clone()),
+                _ => None
+            }
         })
     }
 }
@@ -171,6 +182,13 @@ impl<'a> DataType<'a> {
         }
     }
 
+    pub fn named_fields(&'a self) -> bool {
+        match self {
+            DataType::Struct(s) => s.named_fields,
+            DataType::Enum(_) => panic!("Method 'named_fields' is not supposed to be called in the enum context."),
+        }
+    }
+
     pub fn get_attrs(&'a self) -> &'a DataTypeAttrs {
         match self {
             DataType::Struct(s) => &s.attrs,