Add support for Display and FromStr

README.md

@@ -26,16 +26,17 @@ extern crate bitflags;
 extern crate bitflags_derive;
 
 bitflags! {
-    #[derive(FlagsDebug)]
-    struct Flags: u8 {
+    #[derive(FlagsDisplay, FlagsFromStr)]
+    struct MyFlags: u8 {
         const A = 1;
         const B = 1 << 1;
         const C = 1 << 2;
     }
 }
 
-// The regular `#[derive(Debug)]` would produce "Flags(A | B)" here
-assert_eq!("A | B", format!("{:?}", Flags::A | Flags::B));
+let flags = "A | B".parse::<MyFlags>()?;
+
+assert_eq!("A | B", flags.to_string());
 ```
 
 See [the docs](https://docs.rs/bitflags-derive) for details on all supported attributes.

macros/src/display.rs

@@ -0,0 +1,14 @@
+use proc_macro2::TokenStream;
+
+pub(crate) fn expand(item: syn::DeriveInput) -> Result<TokenStream, syn::Error> {
+    let ident = item.ident;
+    let (impl_generics, ty_generics, where_clause) = item.generics.split_for_impl();
+
+    Ok(
+        quote!(impl #impl_generics bitflags_derive::__private::core::fmt::Display for #ident #ty_generics #where_clause {
+            fn fmt(&self, f: &mut bitflags_derive::__private::core::fmt::Formatter) -> bitflags_derive::__private::core::fmt::Result {
+                bitflags_derive::__private::bitflags::parser::to_writer(self, f)
+            }
+        }),
+    )
+}

macros/src/from_str.rs

@@ -0,0 +1,16 @@
+use proc_macro2::TokenStream;
+
+pub(crate) fn expand(item: syn::DeriveInput) -> Result<TokenStream, syn::Error> {
+    let ident = item.ident;
+    let (impl_generics, ty_generics, where_clause) = item.generics.split_for_impl();
+
+    Ok(
+        quote!(impl #impl_generics bitflags_derive::__private::core::str::FromStr for #ident #ty_generics #where_clause {
+            type Err = bitflags_derive::__private::bitflags::parser::ParseError;
+
+            fn from_str(v: &str) -> bitflags_derive::__private::core::result::Result<Self, bitflags_derive::__private::bitflags::parser::ParseError> {
+                bitflags_derive::__private::bitflags::parser::from_str(v)
+            }
+        }),
+    )
+}

macros/src/lib.rs

@@ -12,9 +12,11 @@ extern crate proc_macro;
 extern crate quote;
 
 mod debug;
+mod display;
+mod from_str;
 
 /**
-Derive [`Debug`](https://doc.rust-lang.org/std/fmt/trait.Debug.html) for a flags type.
+Derive [`Debug`](https://doc.rust-lang.org/std/fmt/trait.Debug.html).
 
 This macro will use [`to_writer`](https://docs.rs/bitflags/latest/bitflags/parser/fn.to_writer.html) to
 format flags values.
@@ -24,6 +26,28 @@ pub fn derive_bitflags_debug(item: proc_macro::TokenStream) -> proc_macro::Token
     debug::expand(syn::parse_macro_input!(item as syn::DeriveInput)).unwrap_or_compile_error()
 }
 
+/**
+Derive [`Display`](https://doc.rust-lang.org/std/fmt/trait.Display.html).
+
+This macro will use [`to_writer`](https://docs.rs/bitflags/latest/bitflags/parser/fn.to_writer.html) to
+format flags values.
+*/
+#[proc_macro_derive(FlagsDisplay)]
+pub fn derive_bitflags_display(item: proc_macro::TokenStream) -> proc_macro::TokenStream {
+    display::expand(syn::parse_macro_input!(item as syn::DeriveInput)).unwrap_or_compile_error()
+}
+
+/**
+Derive [`FromStr`](https://doc.rust-lang.org/std/str/trait.FromStr.html).
+
+This macro will use [`from_str`](https://docs.rs/bitflags/latest/bitflags/parser/fn.from_str.html) to
+parse flags values.
+*/
+#[proc_macro_derive(FlagsFromStr)]
+pub fn derive_bitflags_from_str(item: proc_macro::TokenStream) -> proc_macro::TokenStream {
+    from_str::expand(syn::parse_macro_input!(item as syn::DeriveInput)).unwrap_or_compile_error()
+}
+
 trait ResultExt {
     fn unwrap_or_compile_error(self) -> proc_macro::TokenStream;
 }

src/lib.rs

@@ -22,18 +22,27 @@ extern crate bitflags;
 #[macro_use]
 extern crate bitflags_derive;
 
+# fn main() -> Result<(), bitflags::parser::ParseError> {
 bitflags! {
-    #[derive(FlagsDebug)]
-    struct Flags: u8 {
+    #[derive(FlagsDisplay, FlagsFromStr)]
+    struct MyFlags: u8 {
         const A = 1;
         const B = 1 << 1;
         const C = 1 << 2;
     }
 }
-# fn main() {}
+
+let flags = "A | B".parse::<MyFlags>()?;
+
+assert_eq!("A | B", flags.to_string());
+# Ok(())
+# }
 ```
+
+These derives work for any type that implements the [`Flags`](https://docs.rs/bitflags/latest/bitflags/trait.Flags.html) trait.
 */
 
+#![no_std]
 #![deny(missing_docs)]
 
 #[doc(inline)]

tests/ui/src/display.rs

@@ -0,0 +1,13 @@
+#[test]
+fn derive_display() {
+    bitflags! {
+        #[derive(FlagsDisplay)]
+        struct Flags: u8 {
+            const A = 1;
+            const B = 1 << 1;
+            const C = 1 << 2;
+        }
+    }
+
+    assert_eq!("A | B", (Flags::A | Flags::B).to_string());
+}

tests/ui/src/from_str.rs

@@ -0,0 +1,13 @@
+#[test]
+fn derive_from_str() {
+    bitflags! {
+        #[derive(FlagsFromStr, PartialEq, Eq, Debug)]
+        struct Flags: u8 {
+            const A = 1;
+            const B = 1 << 1;
+            const C = 1 << 2;
+        }
+    }
+
+    assert_eq!("A | B".parse::<Flags>().unwrap(), Flags::A | Flags::B);
+}

tests/ui/src/lib.rs

@@ -7,3 +7,5 @@ extern crate bitflags;
 extern crate bitflags_derive;
 
 mod debug;
+mod display;
+mod from_str;