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§Documentation for Additional Attributes

§Attributes on Enums

Strum supports several custom attributes to modify the generated code. At the enum level, the following attributes are supported:

  • #[strum(serialize_all = "case_style")] attribute can be used to change the case used when serializing to and deserializing from strings. This feature is enabled by withoutboats/heck and supported case styles are:

    • camelCase
    • PascalCase
    • kebab-case
    • snake_case
    • lowercase
    • title_case
    • mixed_case
    use std::string::ToString;
    use strum;
    use strum_macros;
    #[derive(Debug, Eq, PartialEq, strum_macros::ToString)]
    #[strum(serialize_all = "snake_case")]
    enum Brightness {
        Dim {
            glow: usize,
        #[strum(serialize = "bright")]
        Brightness::Dim { glow: 0 }.to_string().as_ref()
  • 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.

§Attributes on Variants

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 be applied multiple times to an element and the enum variant will be parsed if any of them match.

  • to_string="...": Similar to serialize. This value will be included when using FromStr(). More importantly, this specifies what text to use when calling variant.to_string() with the Display derivation, or when calling variant.as_ref() with AsRefStr.

  • default: Applied to a single variant of an enum. The variant must be a Tuple-like variant with a single piece of data that can be create from a &str i.e. T: From<&str>. The generated code will now return the variant with the input string captured as shown below instead of failing.

    // Replaces this:
    _ => Err(strum::ParseError::VariantNotFound)
    // With this in generated code:
    default => Ok(Variant(default.into()))

    The plugin will fail if the data doesn’t implement From<&str>. You can only have one default on your enum.

  • 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 v ariant.

  • 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.

  • detailed_message="..": Adds a more detailed message to a variant. If this value is omitted, then message will be used in it’s place.

  • Structured documentation, as in /// ...: If using EnumMessage, is accessible via get_documentation().

  • props(key="value"): Enables associating additional information with a given variant.