Add #[obake(serde(...))] helper

README.md

@@ -64,7 +64,7 @@ impl From<Foo!["0.1.0"]> for Foo!["0.2.0"] {
 }
 
 // an enumeration of all versions of `Foo` is accessed using the `obake::AnyVersion` type
-// alias.
+// alias
 let versioned_example: obake::AnyVersion<Foo> = (Foo { bar: 42 }).into();
 
 // this enumeration implements `Into<Foo>`, where `Foo` is the latest declared
@@ -78,6 +78,9 @@ assert_eq!(example, Foo { bar: 42 });
 
 - `#[obake(inherit)]`: allows nesting of versioned data-structures.
 - `#[obake(derive(...))]`: allows derive attributes to be applied to generated enums.
+- `#[obake(serde(...))]`: allows [`serde`](https://serde.rs) attributes to be applied to
+  generated `enum`s.
+  - Note: requires the feature `serde`.
 
 ## Limitations
 

obake/Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "obake"
 authors = ["Nathan Corbyn <[email protected]>"]
-version = "1.0.3"
+version = "1.0.4"
 edition = "2018"
 license = "MIT OR Apache-2.0"
 description = "Versioned data-structures for Rust"
@@ -21,3 +21,8 @@ obake_macros = { path = "../obake_macros", version = "1.0" }
 
 [dev-dependencies]
 trybuild = "1.0"
+obake_macros = { path = "../obake_macros", version = "1.0", features = ["serde"] }
+
+[features]
+default = []
+serde = ["obake_macros/serde"]

obake/src/lib.rs

@@ -38,7 +38,7 @@
 //! }
 //!
 //! // an enumeration of all versions of `Foo` is accessed using the `obake::AnyVersion` type
-//! // alias.
+//! // alias
 //! let versioned_example: obake::AnyVersion<Foo> = (Foo { bar: 42 }).into();
 //!
 //! // this enumeration implements `Into<Foo>`, where `Foo` is the latest declared
@@ -52,6 +52,9 @@
 //!
 //! - `#[obake(inherit)]`: allows nesting of versioned data-structures.
 //! - `#[obake(derive(...))]`: allows derive attributes to be applied to generated `enum`s.
+//! - `#[obake(serde(...))]`: allows [`serde`](https://serde.rs) attributes to be applied to
+//!   generated `enum`s.
+//!     - Note: requires the feature `serde`.
 //!
 //! ## Limitations
 //!
@@ -80,9 +83,14 @@
 ///     attributes are treated as a disjunctively).
 /// - `#[obake(derive(...))]` - Apply a derive to the version-tagged enum generated for the
 ///    data-structre.
+/// - `#[obake(serde(...))]` - Apply a [serde] attribute to the version-tagged enum generated
+///   for the data-structre.
+///   - Note: requires the feature `serde`.
 /// - `#[obake(inherit)]` - Marks a field as having an inherited version (i.e., given a field of
 ///   type `Bar`, when marked with `inherit`, this field will be expanded to a field of type
 ///   `Bar![{version}]` in every version).
+///
+/// [serde]: https://serde.rs
 // TODO(@doctorn) document generated types and trait implementations
 pub use obake_macros::versioned;
 

obake/tests/ui/bad_helpers.rs

@@ -56,4 +56,29 @@ mod derives {
     }
 }
 
+mod serdes {
+    #[obake::versioned]
+    #[obake(version("0.1.0"))]
+    struct Foo {
+        #[obake(serde(skip_serializing))]
+        field_0: u32,
+    }
+
+    #[obake::versioned]
+    #[obake(version("0.1.0"))]
+    enum Bar {
+        #[obake(serde(skip_serializing))]
+        X,
+    }
+
+    #[obake::versioned]
+    #[obake(version("0.1.0"))]
+    enum Baz {
+        X {
+            #[obake(serde(skip_serializing))]
+            field_0: u32,
+        },
+    }
+}
+
 fn main() {}

obake/tests/ui/bad_helpers.stderr

@@ -45,3 +45,21 @@ error: `#[obake(derive(...))]` not valid in this context
    |
 53 |             #[obake(derive(Clone))]
    |                     ^^^^^^
+
+error: `#[obake(serde(...))]` not valid in this context
+  --> $DIR/bad_helpers.rs:63:17
+   |
+63 |         #[obake(serde(skip_serializing))]
+   |                 ^^^^^
+
+error: `#[obake(serde(...))]` not valid in this context
+  --> $DIR/bad_helpers.rs:70:17
+   |
+70 |         #[obake(serde(skip_serializing))]
+   |                 ^^^^^
+
+error: `#[obake(serde(...))]` not valid in this context
+  --> $DIR/bad_helpers.rs:78:21
+   |
+78 |             #[obake(serde(skip_serializing))]
+   |                     ^^^^^

obake_macros/Cargo.toml

@@ -1,7 +1,7 @@
 [package]
 name = "obake_macros"
 authors = ["Nathan Corbyn <[email protected]>"]
-version = "1.0.3"
+version = "1.0.4"
 edition = "2018"
 license = "MIT OR Apache-2.0"
 description = "Macros for versioned data-structures"
@@ -22,3 +22,7 @@ proc-macro2 = "1.0"
 quote = "1.0"
 syn = { version = "1.0", features = ["full"] }
 semver = "1.0"
+
+[features]
+default = []
+serde = []

obake_macros/src/expand.rs

@@ -59,6 +59,14 @@ impl VersionedField {
             ));
         }
 
+        #[cfg(feature = "serde")]
+        if let Some(serde) = self.attrs.serdes().next() {
+            return Err(syn::Error::new(
+                serde.span,
+                "`#[obake(serde(...))]` not valid in this context",
+            ));
+        }
+
         let mut reqs: Vec<_> = self.attrs.cfgs().map(|attr| attr.req.clone()).collect();
 
         // If we have no `#[obake(cfg(...))]` attributes, default to `#[obake(cfg("*"))]`
@@ -122,13 +130,21 @@ impl VersionedVariant {
             ));
         }
 
-        if let Some(inherit) = self.attrs.derives().next() {
+        if let Some(derive) = self.attrs.derives().next() {
             return Err(syn::Error::new(
-                inherit.span,
+                derive.span,
                 "`#[obake(derive(...))]` not valid in this context",
             ));
         }
 
+        #[cfg(feature = "serde")]
+        if let Some(serde) = self.attrs.serdes().next() {
+            return Err(syn::Error::new(
+                serde.span,
+                "`#[obake(serde(...))]` not valid in this context",
+            ));
+        }
+
         let mut reqs: Vec<_> = self.attrs.cfgs().map(|attr| attr.req.clone()).collect();
 
         // If we have no `#[obake(cfg(...))]` attributes, default to `#[obake(cfg("*"))]`
@@ -303,6 +319,11 @@ impl VersionedItem {
             let tokens = &attr.tokens;
             quote!(#[derive(#tokens)])
         });
+        #[cfg(feature = "serde")]
+        let derives = derives.chain(self.attrs.serdes().map(|attr| {
+            let tokens = &attr.tokens;
+            quote!(#[serde(#tokens)])
+        }));
 
         quote! {
             #[doc(hidden)]

obake_macros/src/internal.rs

@@ -48,12 +48,21 @@ pub struct DeriveAttr {
     pub tokens: TokenStream2,
 }
 
+#[cfg(feature = "serde")]
+#[derive(Clone)]
+pub struct SerdeAttr {
+    pub span: Span,
+    pub tokens: TokenStream2,
+}
+
 #[derive(Clone)]
 pub enum ObakeAttribute {
     Version(VersionAttr),
     Cfg(CfgAttr),
     Inherit(InheritAttr),
     Derive(DeriveAttr),
+    #[cfg(feature = "serde")]
+    Serde(SerdeAttr),
 }
 
 #[derive(Clone)]
@@ -108,6 +117,15 @@ impl ObakeAttribute {
             _ => None,
         }
     }
+
+    #[cfg(feature = "serde")]
+    pub fn serde(&self) -> Option<&SerdeAttr> {
+        #![allow(clippy::match_wildcard_for_single_variants)]
+        match &self {
+            ObakeAttribute::Serde(serde) => Some(serde),
+            _ => None,
+        }
+    }
 }
 
 impl VersionedAttribute {
@@ -149,6 +167,11 @@ impl VersionedAttributes {
         self.obake().filter_map(ObakeAttribute::derive)
     }
 
+    #[cfg(feature = "serde")]
+    pub fn serdes(&self) -> impl Iterator<Item = &SerdeAttr> + '_ {
+        self.obake().filter_map(ObakeAttribute::serde)
+    }
+
     pub fn attrs(&self) -> impl Iterator<Item = &syn::Attribute> + '_ {
         self.attrs.iter().filter_map(VersionedAttribute::attr)
     }

obake_macros/src/parse.rs

@@ -53,6 +53,15 @@ impl Parse for ObakeAttribute {
                     tokens: content.parse()?,
                 })
             }
+            #[cfg(feature = "serde")]
+            _ if ident == "serde" => {
+                let content;
+                parenthesized!(content in input);
+                Self::Serde(SerdeAttr {
+                    span: ident.span(),
+                    tokens: content.parse()?,
+                })
+            }
             _ => {
                 return Err(syn::Error::new(
                     ident.span(),