Allow deriving PrimaryKeyType (#245)

butane/src/lib.rs

@@ -6,7 +6,7 @@
 
 #![deny(missing_docs)]
 
-pub use butane_codegen::{butane_type, dataresult, model, FieldType};
+pub use butane_codegen::{butane_type, dataresult, model, FieldType, PrimaryKeyType};
 pub use butane_core::custom;
 pub use butane_core::fkey::ForeignKey;
 pub use butane_core::internal;

butane_codegen/src/lib.rs

@@ -433,3 +433,19 @@ fn derive_field_type_with_json(struct_name: &Ident) -> TokenStream {
 fn derive_field_type_with_json(_struct_name: &Ident) -> TokenStream {
     panic!("Feature 'json' is required to derive FieldType")
 }
+
+/// Derive macro for marker trait `PrimaryKeyType`.
+/// E.g.
+/// ```ignore
+/// #[derive(FieldType, PrimaryKeyType)]
+/// pub struct PostId(pub uuid::Uuid);
+/// ```
+#[proc_macro_derive(PrimaryKeyType)]
+pub fn derive_primary_key_type(input: TokenStream) -> TokenStream {
+    let derive_input = syn::parse_macro_input!(input as syn::DeriveInput);
+    let ident = &derive_input.ident;
+    quote!(
+        impl butane::PrimaryKeyType for #ident {}
+    )
+    .into()
+}

docs/newtype.md

@@ -45,17 +45,15 @@ Create `src/models.rs` with a `BlogId` and `PostId` struct wrapping a `uuid`.
 use butane::{FieldType, PrimaryKeyType};
 use serde::{Deserialize, Serialize};
 
-#[derive(Clone, Debug, Default, Deserialize, Serialize, FieldType, PartialEq, Eq)]
+#[derive(Clone, Debug, Default, Deserialize, Eq, FieldType, PartialEq, PrimaryKeyType, Serialize)]
 pub struct BlogId(pub uuid::Uuid);
-impl PrimaryKeyType for BlogId {}
 
-#[derive(Clone, Debug, Default, Deserialize, Serialize, FieldType, PartialEq, Eq)]
+#[derive(Clone, Debug, Default, Deserialize, Eq, FieldType, PartialEq, PrimaryKeyType, Serialize)]
 pub struct PostId(pub uuid::Uuid);
-impl PrimaryKeyType for PostId {}
 ```
 
-For each, `FieldType` is derived, and they implement the marker trait `PrimaryKeyType`
-to allow their use as a primary key.
+For each, `FieldType` is derived to generate code to describe how the field will be stored, and
+the marker trait `PrimaryKeyType` is derived to allow their use as a primary key.
 
 As Butane natively supports `uuid`, these newtypes will be stored in the butane metadata as
 "Blob" type, which is stored in the database using an appropriate column type based on the

examples/newtype/src/models.rs

@@ -5,14 +5,16 @@ use garde::Validate;
 use serde::{Deserialize, Serialize};
 
 /// Blog identifier.
-#[derive(Clone, Debug, Default, Deserialize, Eq, FieldType, PartialEq, Serialize)]
+#[derive(
+    Clone, Debug, Default, Deserialize, Eq, FieldType, PartialEq, PrimaryKeyType, Serialize,
+)]
 pub struct BlogId(pub uuid::Uuid);
-impl PrimaryKeyType for BlogId {}
 
 /// Post identifier.
-#[derive(Clone, Debug, Default, Deserialize, Eq, FieldType, PartialEq, Serialize)]
+#[derive(
+    Clone, Debug, Default, Deserialize, Eq, FieldType, PartialEq, PrimaryKeyType, Serialize,
+)]
 pub struct PostId(pub uuid::Uuid);
-impl PrimaryKeyType for PostId {}
 
 /// Blog name.
 #[derive(Clone, Debug, Default, Deserialize, Eq, FieldType, PartialEq, Serialize, Validate)]