Merge branch 'feat/static-variants-array' of https://github.com/Synde…

…lis/strum into Syndelis-feat/static-variants-array

README.md

@@ -47,6 +47,7 @@ Strum has implemented the following macros:
 | [EnumMessage] | Add a verbose message to an enum variant. |
 | [EnumDiscriminants] | Generate a new type with only the discriminant names. |
 | [EnumCount] | Add a constant `usize` equal to the number of variants. |
+| [StaticVariantsArray] | Adds an associated `ALL_VARIANTS` constant which is an array of all enum discriminants |
 
 # Contributing
 
@@ -81,3 +82,4 @@ Strumming is also a very whimsical motion, much like writing Rust code.
 [EnumDiscriminants]: https://docs.rs/strum_macros/0.25/strum_macros/derive.EnumDiscriminants.html
 [EnumCount]: https://docs.rs/strum_macros/0.25/strum_macros/derive.EnumCount.html
 [FromRepr]: https://docs.rs/strum_macros/0.25/strum_macros/derive.FromRepr.html
+[StaticVariantsArray]: https://docs.rs/strum_macros/0.25/strum_macros/derive.StaticVariantsArray.html

strum/src/lib.rs

@@ -213,6 +213,16 @@ pub trait VariantNames {
     const VARIANTS: &'static [&'static str];
 }
 
+/// A trait for retrieving a static array containing all the variants in an Enum.
+/// This trait can be autoderived by `strum_macros`. For derived usage, all the
+/// variants in the enumerator need to be unit-types, which means you can't autoderive
+/// enums with inner data in one or more variants. Consider using it alongside
+/// [`EnumDiscriminants`] if you require inner data but still want to have an
+/// static array of variants.
+pub trait StaticVariantsArray: std::marker::Sized + 'static {
+    const ALL_VARIANTS: &'static [Self];
+}
+
 #[cfg(feature = "derive")]
 pub use strum_macros::*;
 
@@ -243,5 +253,6 @@ DocumentMacroRexports! {
     EnumVariantNames,
     FromRepr,
     IntoStaticStr,
-    ToString
+    ToString,
+    StaticVariantsArray
 }

strum_macros/Cargo.toml

@@ -26,4 +26,4 @@ rustversion = "1.0"
 syn = { version = "2.0", features = ["parsing", "extra-traits"] }
 
 [dev-dependencies]
-strum = "0.25"
+strum = { path = "../strum" }

strum_macros/src/helpers/mod.rs

@@ -17,6 +17,14 @@ pub fn non_enum_error() -> syn::Error {
     syn::Error::new(Span::call_site(), "This macro only supports enums.")
 }
 
+pub fn non_unit_variant_error() -> syn::Error {
+    syn::Error::new(
+        Span::call_site(),
+        "This macro only supports enums of strictly unit variants. Consider \
+        using it in conjunction with [`EnumDiscriminants`]"
+    )
+}
+
 pub fn strum_discriminants_passthrough_error(span: &impl Spanned) -> syn::Error {
     syn::Error::new(
         span.span(),

strum_macros/src/lib.rs

@@ -194,6 +194,37 @@ pub fn variant_names(input: proc_macro::TokenStream) -> proc_macro::TokenStream
     toks.into()
 }
 
+/// Adds a static array with all of the Enum's variants.
+/// 
+/// Implements `Strum::StaticVariantsArray` which adds an associated constant `ALL_VARIANTS`.
+/// This constant contains an array with all the variants of the enumerator.
+/// 
+/// This trait can only be autoderived if the enumerator is composed only of unit-type variants,
+/// meaning that the variants must not have any data.
+/// 
+/// ```
+/// use strum::StaticVariantsArray;
+/// 
+/// #[derive(StaticVariantsArray, Debug, PartialEq, Eq)]
+/// enum Op {
+///     Add,
+///     Sub,
+///     Mul,
+///     Div,
+/// }
+/// 
+/// assert_eq!(Op::ALL_VARIANTS, &[Op::Add, Op::Sub, Op::Mul, Op::Div]);
+/// ```
+#[proc_macro_derive(StaticVariantsArray, attributes(strum))]
+pub fn static_variants_array(input: proc_macro::TokenStream) -> proc_macro::TokenStream {
+    let ast = syn::parse_macro_input!(input as DeriveInput);
+
+    let toks = macros::static_variants_array::static_variants_array_inner(&ast)
+        .unwrap_or_else(|err| err.to_compile_error());
+    debug_print_generated(&ast, &toks);
+    toks.into()
+}
+
 #[proc_macro_derive(AsStaticStr, attributes(strum))]
 #[deprecated(
     since = "0.22.0",
@@ -736,7 +767,7 @@ pub fn enum_properties(input: proc_macro::TokenStream) -> proc_macro::TokenStrea
 /// // Bring trait into scope
 /// use std::str::FromStr;
 /// use strum::{IntoEnumIterator, EnumMessage};
-/// use strum_macros::{EnumDiscriminants, EnumIter, EnumString, EnumMessage};
+/// use strum_macros::{EnumDiscriminants, EnumIter, EnumString};
 ///
 /// #[derive(Debug)]
 /// struct NonDefault;

strum_macros/src/macros/mod.rs

@@ -8,6 +8,7 @@ pub mod enum_properties;
 pub mod enum_try_as;
 pub mod enum_variant_names;
 pub mod from_repr;
+pub mod static_variants_array;
 
 mod strings;
 

strum_macros/src/macros/static_variants_array.rs

@@ -0,0 +1,36 @@
+use proc_macro2::TokenStream;
+use quote::quote;
+use syn::{Data, DeriveInput, Fields};
+
+use crate::helpers::{non_enum_error, HasTypeProperties, non_unit_variant_error};
+
+pub fn static_variants_array_inner(ast: &DeriveInput) -> syn::Result<TokenStream> {
+    let name = &ast.ident;
+    let gen = &ast.generics;
+    let (impl_generics, ty_generics, where_clause) = gen.split_for_impl();
+
+    let variants = match &ast.data {
+        Data::Enum(v) => &v.variants,
+        _ => return Err(non_enum_error()),
+    };
+
+    let type_properties = ast.get_type_properties()?;
+    let strum_module_path = type_properties.crate_module_path();
+
+    let idents = variants
+        .iter()
+        .cloned()
+        .map(|v| {
+            match v.fields {
+                Fields::Unit => Ok(v.ident),
+                _ => Err(non_unit_variant_error())
+            }
+        })
+        .collect::<syn::Result<Vec<_>>>()?;
+
+    Ok(quote! {
+        impl #impl_generics #strum_module_path::StaticVariantsArray for #name #ty_generics #where_clause {
+            const ALL_VARIANTS: &'static [Self] = &[ #(#name::#idents),* ];
+        }
+    })
+}

strum_tests/tests/static_variants_array.rs

@@ -0,0 +1,87 @@
+use strum::{StaticVariantsArray, EnumDiscriminants};
+
+mod core {} // ensure macros call `::core`
+
+#[test]
+fn simple() {
+    #[derive(StaticVariantsArray, PartialEq, Eq, Debug)]
+    enum Operation {
+        Add,
+        Sub,
+        Mul,
+        Div,
+    }
+
+    assert_eq!(
+        Operation::ALL_VARIANTS,
+        &[
+            Operation::Add,
+            Operation::Sub,
+            Operation::Mul,
+            Operation::Div,
+        ]
+    );
+}
+
+#[test]
+fn in_enum_discriminants() {
+    #[allow(dead_code)]
+    #[derive(EnumDiscriminants)]
+    #[strum_discriminants(derive(StaticVariantsArray))]
+    #[strum_discriminants(name(GeometricShapeDiscriminants))]
+    enum GeometricShape {
+        Point,
+        Circle(i32),
+        Rectangle {
+            width: i32,
+            height: i32,
+        }
+    }
+
+    assert_eq!(
+        GeometricShapeDiscriminants::ALL_VARIANTS,
+        &[
+            GeometricShapeDiscriminants::Point,
+            GeometricShapeDiscriminants::Circle,
+            GeometricShapeDiscriminants::Rectangle,
+        ]
+    );
+}
+
+#[test]
+fn empty_enum() {
+    #[derive(StaticVariantsArray, PartialEq, Eq, Debug)]
+    enum Empty {}
+
+    assert_eq!(
+        Empty::ALL_VARIANTS,
+        &[],
+    );
+}
+
+#[test]
+fn variants_with_values() {
+    #[derive(StaticVariantsArray, PartialEq, Eq, Debug)]
+    enum WeekDay {
+        Sunday = 0,
+        Monday = 1,
+        Tuesday = 2,
+        Wednesday = 3,
+        Thursday = 4,
+        Friday = 5,
+        Saturday = 6,
+    }
+
+    assert_eq!(
+        WeekDay::ALL_VARIANTS,
+        &[
+            WeekDay::Sunday,
+            WeekDay::Monday,
+            WeekDay::Tuesday,
+            WeekDay::Wednesday,
+            WeekDay::Thursday,
+            WeekDay::Friday,
+            WeekDay::Saturday,
+        ],
+    );
+}