Support case-insensitive EnumString (#157)

Fixes #154

strum/src/additional_attributes.rs

@@ -34,6 +34,9 @@
 //! );
 //! ```
 //!
+//! You can also apply the `#[strum(ascii_case_insensitive)]` attribute to the enum,
+//! and this has the same effect of applying it to every variant.
+//!
 //! Custom attributes are applied to a variant by adding `#[strum(parameter="value")]` to the variant.
 //!
 //! - `serialize="..."`: Changes the text that `FromStr()` looks for when parsing a string. This attribute can
@@ -58,6 +61,10 @@
 //!
 //! - `disabled`: removes variant from generated code.
 //!
+//! - `ascii_case_insensitive`: makes the comparison to this variant case insensitive (ASCII only).
+//!   If the whole enum is marked `ascii_case_insensitive`, you can specify `ascii_case_insensitive = false`
+//!   to disable case insensitivity on this variant.
+//!
 //! - `message=".."`: Adds a message to enum variant. This is used in conjunction with the `EnumMessage`
 //!    trait to associate a message with a variant. If `detailed_message` is not provided,
 //!    then `message` will also be returned when get_detailed_message() is called.

strum_macros/src/helpers/metadata.rs

@@ -4,7 +4,7 @@ use syn::{
     parse::{Parse, ParseStream},
     punctuated::Punctuated,
     spanned::Spanned,
-    Attribute, DeriveInput, Ident, LitStr, Path, Token, Variant, Visibility,
+    Attribute, DeriveInput, Ident, LitBool, LitStr, Path, Token, Variant, Visibility,
 };
 
 use super::case_style::CaseStyle;
@@ -28,28 +28,39 @@ pub mod kw {
     custom_keyword!(disabled);
     custom_keyword!(default);
     custom_keyword!(props);
+    custom_keyword!(ascii_case_insensitive);
 }
 
 pub enum EnumMeta {
     SerializeAll {
         kw: kw::serialize_all,
         case_style: CaseStyle,
     },
+    AsciiCaseInsensitive(kw::ascii_case_insensitive),
 }
 
 impl Parse for EnumMeta {
     fn parse(input: ParseStream) -> syn::Result<Self> {
-        let kw = input.parse::<kw::serialize_all>()?;
-        input.parse::<Token![=]>()?;
-        let case_style = input.parse()?;
-        Ok(EnumMeta::SerializeAll { kw, case_style })
+        let lookahead = input.lookahead1();
+        if lookahead.peek(kw::serialize_all) {
+            let kw = input.parse::<kw::serialize_all>()?;
+            input.parse::<Token![=]>()?;
+            let case_style = input.parse()?;
+            Ok(EnumMeta::SerializeAll { kw, case_style })
+        } else if lookahead.peek(kw::ascii_case_insensitive) {
+            let kw = input.parse()?;
+            Ok(EnumMeta::AsciiCaseInsensitive(kw))
+        } else {
+            Err(lookahead.error())
+        }
     }
 }
 
 impl Spanned for EnumMeta {
     fn span(&self) -> Span {
         match self {
             EnumMeta::SerializeAll { kw, .. } => kw.span(),
+            EnumMeta::AsciiCaseInsensitive(kw) => kw.span(),
         }
     }
 }
@@ -142,6 +153,10 @@ pub enum VariantMeta {
     },
     Disabled(kw::disabled),
     Default(kw::default),
+    AsciiCaseInsensitive {
+        kw: kw::ascii_case_insensitive,
+        value: bool,
+    },
     Props {
         kw: kw::props,
         props: Vec<(LitStr, LitStr)>,
@@ -175,6 +190,15 @@ impl Parse for VariantMeta {
             Ok(VariantMeta::Disabled(input.parse()?))
         } else if lookahead.peek(kw::default) {
             Ok(VariantMeta::Default(input.parse()?))
+        } else if lookahead.peek(kw::ascii_case_insensitive) {
+            let kw = input.parse()?;
+            let value = if input.peek(Token![=]) {
+                let _: Token![=] = input.parse()?;
+                input.parse::<LitBool>()?.value()
+            } else {
+                true
+            };
+            Ok(VariantMeta::AsciiCaseInsensitive { kw, value })
         } else if lookahead.peek(kw::props) {
             let kw = input.parse()?;
             let content;
@@ -216,6 +240,7 @@ impl Spanned for VariantMeta {
             VariantMeta::ToString { kw, .. } => kw.span,
             VariantMeta::Disabled(kw) => kw.span,
             VariantMeta::Default(kw) => kw.span,
+            VariantMeta::AsciiCaseInsensitive { kw, .. } => kw.span,
             VariantMeta::Props { kw, .. } => kw.span,
         }
     }

strum_macros/src/helpers/type_props.rs

@@ -14,6 +14,7 @@ pub trait HasTypeProperties {
 #[derive(Debug, Clone, Default)]
 pub struct StrumTypeProperties {
     pub case_style: Option<CaseStyle>,
+    pub ascii_case_insensitive: bool,
     pub discriminant_derives: Vec<Path>,
     pub discriminant_name: Option<Ident>,
     pub discriminant_others: Vec<TokenStream>,
@@ -28,6 +29,7 @@ impl HasTypeProperties for DeriveInput {
         let discriminants_meta = self.get_discriminants_metadata()?;
 
         let mut serialize_all_kw = None;
+        let mut ascii_case_insensitive_kw = None;
         for meta in strum_meta {
             match meta {
                 EnumMeta::SerializeAll { case_style, kw } => {
@@ -38,6 +40,14 @@ impl HasTypeProperties for DeriveInput {
                     serialize_all_kw = Some(kw);
                     output.case_style = Some(case_style);
                 }
+                EnumMeta::AsciiCaseInsensitive(kw) => {
+                    if let Some(fst_kw) = ascii_case_insensitive_kw {
+                        return Err(occurrence_error(fst_kw, kw, "ascii_case_insensitive"));
+                    }
+
+                    ascii_case_insensitive_kw = Some(kw);
+                    output.ascii_case_insensitive = true;
+                }
             }
         }
 

strum_macros/src/helpers/variant_props.rs

@@ -13,6 +13,7 @@ pub trait HasStrumVariantProperties {
 pub struct StrumVariantProperties {
     pub disabled: Option<kw::disabled>,
     pub default: Option<kw::default>,
+    pub ascii_case_insensitive: Option<bool>,
     pub message: Option<LitStr>,
     pub detailed_message: Option<LitStr>,
     pub string_props: Vec<(LitStr, LitStr)>,
@@ -65,6 +66,7 @@ impl HasStrumVariantProperties for Variant {
         let mut to_string_kw = None;
         let mut disabled_kw = None;
         let mut default_kw = None;
+        let mut ascii_case_insensitive_kw = None;
         for meta in self.get_metadata()? {
             match meta {
                 VariantMeta::Message { value, kw } => {
@@ -110,6 +112,14 @@ impl HasStrumVariantProperties for Variant {
                     default_kw = Some(kw);
                     output.default = Some(kw);
                 }
+                VariantMeta::AsciiCaseInsensitive { kw, value } => {
+                    if let Some(fst_kw) = ascii_case_insensitive_kw {
+                        return Err(occurrence_error(fst_kw, kw, "ascii_case_insensitive"));
+                    }
+
+                    ascii_case_insensitive_kw = Some(kw);
+                    output.ascii_case_insensitive = Some(value);
+                }
                 VariantMeta::Props { props, .. } => {
                     output.string_props.extend(props);
                 }

strum_macros/src/lib.rs

@@ -66,6 +66,10 @@ fn debug_print_generated(ast: &DeriveInput, toks: &TokenStream) {
 ///     // Notice that we can disable certain variants from being found
 ///     #[strum(disabled)]
 ///     Yellow,
+///
+///     // We can make the comparison case insensitive (however Unicode is not supported at the moment)
+///     #[strum(ascii_case_insensitive)]
+///     Black,
 /// }
 ///
 /// /*
@@ -77,7 +81,9 @@ fn debug_print_generated(ast: &DeriveInput, toks: &TokenStream) {
 ///         match s {
 ///             "Red" => ::std::result::Result::Ok(Color::Red),
 ///             "Green" => ::std::result::Result::Ok(Color::Green { range:Default::default() }),
-///             "blue" | "b" => ::std::result::Result::Ok(Color::Blue(Default::default())),
+///             "blue" => ::std::result::Result::Ok(Color::Blue(Default::default())),
+///             "b" => ::std::result::Result::Ok(Color::Blue(Default::default())),
+///             s if s.eq_ignore_ascii_case("Black") => ::std::result::Result::Ok(Color::Black),
 ///             _ => ::std::result::Result::Err(::strum::ParseError::VariantNotFound),
 ///         }
 ///     }
@@ -95,6 +101,8 @@ fn debug_print_generated(ast: &DeriveInput, toks: &TokenStream) {
 /// assert!(color_variant.is_err());
 /// // however the variant is still normally usable
 /// println!("{:?}", Color::Yellow);
+/// let color_variant = Color::from_str("bLACk").unwrap();
+/// assert_eq!(Color::Black, color_variant);
 /// ```
 #[proc_macro_derive(EnumString, attributes(strum))]
 pub fn from_string(input: proc_macro::TokenStream) -> proc_macro::TokenStream {

strum_macros/src/macros/strings/from_string.rs

@@ -50,8 +50,20 @@ pub fn from_string_inner(ast: &DeriveInput) -> syn::Result<TokenStream> {
             continue;
         }
 
+        let is_ascii_case_insensitive = variant_properties
+            .ascii_case_insensitive
+            .unwrap_or(type_properties.ascii_case_insensitive);
         // If we don't have any custom variants, add the default serialized name.
-        let attrs = variant_properties.get_serializations(type_properties.case_style);
+        let attrs = variant_properties
+            .get_serializations(type_properties.case_style)
+            .into_iter()
+            .map(|serialization| {
+                if is_ascii_case_insensitive {
+                    quote! { s if s.eq_ignore_ascii_case(#serialization) }
+                } else {
+                    quote! { #serialization }
+                }
+            });
 
         let params = match &variant.fields {
             Fields::Unit => quote! {},
@@ -69,7 +81,7 @@ pub fn from_string_inner(ast: &DeriveInput) -> syn::Result<TokenStream> {
             }
         };
 
-        arms.push(quote! { #(#attrs)|* => ::std::result::Result::Ok(#name::#ident #params) });
+        arms.push(quote! { #(#attrs => ::std::result::Result::Ok(#name::#ident #params)),* });
     }
 
     arms.push(default);

strum_tests/tests/from_str.rs

@@ -13,6 +13,8 @@ enum Color {
     Green(String),
     #[strum(to_string = "purp")]
     Purple,
+    #[strum(serialize = "blk", serialize = "Black", ascii_case_insensitive)]
+    Black,
 }
 
 #[test]
@@ -44,6 +46,12 @@ fn color_default() {
     );
 }
 
+#[test]
+fn color_ascii_case_insensitive() {
+    assert_eq!(Color::Black, Color::from_str("BLK").unwrap());
+    assert_eq!(Color::Black, Color::from_str("bLaCk").unwrap());
+}
+
 #[derive(Debug, Eq, PartialEq, EnumString)]
 #[strum(serialize_all = "snake_case")]
 enum Brightness {
@@ -122,3 +130,42 @@ enum Generic<T: Default> {
 fn generic_test() {
     assert_eq!(Generic::Gen(""), Generic::from_str("Gen").unwrap());
 }
+
+#[derive(Debug, Eq, PartialEq, EnumString)]
+#[strum(ascii_case_insensitive)]
+enum CaseInsensitiveEnum {
+    NoAttr,
+    #[strum(ascii_case_insensitive = false)]
+    NoCaseInsensitive,
+    #[strum(ascii_case_insensitive = true)]
+    CaseInsensitive,
+}
+
+#[test]
+fn case_insensitive_enum_no_attr() {
+    assert_eq!(
+        CaseInsensitiveEnum::NoAttr,
+        CaseInsensitiveEnum::from_str("noattr").unwrap()
+    );
+}
+
+#[test]
+fn case_insensitive_enum_no_case_insensitive() {
+    assert_eq!(
+        CaseInsensitiveEnum::NoCaseInsensitive,
+        CaseInsensitiveEnum::from_str("NoCaseInsensitive").unwrap(),
+    );
+    assert!(CaseInsensitiveEnum::from_str("nocaseinsensitive").is_err());
+}
+
+#[test]
+fn case_insensitive_enum_case_insensitive() {
+    assert_eq!(
+        CaseInsensitiveEnum::CaseInsensitive,
+        CaseInsensitiveEnum::from_str("CaseInsensitive").unwrap(),
+    );
+    assert_eq!(
+        CaseInsensitiveEnum::CaseInsensitive,
+        CaseInsensitiveEnum::from_str("caseinsensitive").unwrap(),
+    );
+}