# attr.rs - source
Source of the Rust file `/home/justine/.cargo/registry/src/github.com-1ecc6299db9ec823/clap_derive-4.0.21/src/attr.rs`.
Keywords: rust, rustlang, rust-lang

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    use std::iter::FromIterator;

    use proc_macro2::TokenStream;
    use proc_macro_error::abort;
    use proc_macro_error::ResultExt;
    use quote::quote;
    use quote::ToTokens;
    use syn::spanned::Spanned;
    use syn::{
        parenthesized,
        parse::{Parse, ParseStream},
        punctuated::Punctuated,
        Attribute, Expr, Ident, LitStr, Token,
    };

    use crate::utils::Sp;

    #[derive(Clone)]
    pub struct ClapAttr {
        pub kind: Sp<AttrKind>,
        pub name: Ident,
        pub magic: Option<MagicAttrName>,
        pub value: Option<AttrValue>,
    }

    impl ClapAttr {
        pub fn parse_all(all_attrs: &[Attribute]) -> Vec<Self> {
            all_attrs
                .iter()
                .filter_map(|attr| {
                    let kind = if attr.path.is_ident("clap") {
                        Some(Sp::new(AttrKind::Clap, attr.path.span()))
                    } else if attr.path.is_ident("structopt") {
                        Some(Sp::new(AttrKind::StructOpt, attr.path.span()))
                    } else if attr.path.is_ident("command") {
                        Some(Sp::new(AttrKind::Command, attr.path.span()))
                    } else if attr.path.is_ident("group") {
                        Some(Sp::new(AttrKind::Group, attr.path.span()))
                    } else if attr.path.is_ident("arg") {
                        Some(Sp::new(AttrKind::Arg, attr.path.span()))
                    } else if attr.path.is_ident("value") {
                        Some(Sp::new(AttrKind::Value, attr.path.span()))
                    } else {
                        None
                    };
                    kind.map(|k| (k, attr))
                })
                .flat_map(|(k, attr)| {
                    attr.parse_args_with(Punctuated::<ClapAttr, Token![,]>::parse_terminated)
                        .unwrap_or_abort()
                        .into_iter()
                        .map(move |mut a| {
                            a.kind = k;
                            a
                        })
                })
                .collect()
        }

        pub fn value_or_abort(&self) -> &AttrValue {
            self.value
                .as_ref()
                .unwrap_or_else(|| abort!(self.name, "attribute `{}` requires a value", self.name))
        }

        pub fn lit_str_or_abort(&self) -> &LitStr {
            let value = self.value_or_abort();
            match value {
                AttrValue::LitStr(tokens) => tokens,
                AttrValue::Expr(_) | AttrValue::Call(_) => {
                    abort!(
                        self.name,
                        "attribute `{}` can only accept string litersl",
                        self.name
                    )
                }
            }
        }
    }

    impl Parse for ClapAttr {
        fn parse(input: ParseStream) -> syn::Result<Self> {
            let name: Ident = input.parse()?;
            let name_str = name.to_string();

            let magic = match name_str.as_str() {
                "rename_all" => Some(MagicAttrName::RenameAll),
                "rename_all_env" => Some(MagicAttrName::RenameAllEnv),
                "skip" => Some(MagicAttrName::Skip),
                "next_display_order" => Some(MagicAttrName::NextDisplayOrder),
                "next_help_heading" => Some(MagicAttrName::NextHelpHeading),
                "default_value_t" => Some(MagicAttrName::DefaultValueT),
                "default_values_t" => Some(MagicAttrName::DefaultValuesT),
                "default_value_os_t" => Some(MagicAttrName::DefaultValueOsT),
                "default_values_os_t" => Some(MagicAttrName::DefaultValuesOsT),
                "long" => Some(MagicAttrName::Long),
                "short" => Some(MagicAttrName::Short),
                "value_parser" => Some(MagicAttrName::ValueParser),
                "action" => Some(MagicAttrName::Action),
                "env" => Some(MagicAttrName::Env),
                "flatten" => Some(MagicAttrName::Flatten),
                "value_enum" => Some(MagicAttrName::ValueEnum),
                "from_global" => Some(MagicAttrName::FromGlobal),
                "subcommand" => Some(MagicAttrName::Subcommand),
                "external_subcommand" => Some(MagicAttrName::ExternalSubcommand),
                "verbatim_doc_comment" => Some(MagicAttrName::VerbatimDocComment),
                "about" => Some(MagicAttrName::About),
                "long_about" => Some(MagicAttrName::LongAbout),
                "long_help" => Some(MagicAttrName::LongHelp),
                "author" => Some(MagicAttrName::Author),
                "version" => Some(MagicAttrName::Version),
                _ => None,
            };

            let value = if input.peek(Token![=]) {
                // `name = value` attributes.
                let assign_token = input.parse::<Token![=]>()?; // skip '='
                if input.peek(LitStr) {
                    let lit: LitStr = input.parse()?;
                    Some(AttrValue::LitStr(lit))
                } else {
                    match input.parse::<Expr>() {
                        Ok(expr) => Some(AttrValue::Expr(expr)),

                        Err(_) => abort! {
                            assign_token,
                            "expected `string literal` or `expression` after `=`"
                        },
                    }
                }
            } else if input.peek(syn::token::Paren) {
                // `name(...)` attributes.
                let nested;
                parenthesized!(nested in input);

                let method_args: Punctuated<_, Token![,]> = nested.parse_terminated(Expr::parse)?;
                Some(AttrValue::Call(Vec::from_iter(method_args)))
            } else {
                None
            };

            Ok(Self {
                kind: Sp::new(AttrKind::Clap, name.span()),
                name,
                magic,
                value,
            })
        }
    }

    #[derive(Copy, Clone, PartialEq, Eq)]
    pub enum MagicAttrName {
        Short,
        Long,
        ValueParser,
        Action,
        Env,
        Flatten,
        ValueEnum,
        FromGlobal,
        Subcommand,
        VerbatimDocComment,
        ExternalSubcommand,
        About,
        LongAbout,
        LongHelp,
        Author,
        Version,
        RenameAllEnv,
        RenameAll,
        Skip,
        DefaultValueT,
        DefaultValuesT,
        DefaultValueOsT,
        DefaultValuesOsT,
        NextDisplayOrder,
        NextHelpHeading,
    }

    #[derive(Clone)]
    #[allow(clippy::large_enum_variant)]
    pub enum AttrValue {
        LitStr(LitStr),
        Expr(Expr),
        Call(Vec<Expr>),
    }

    impl ToTokens for AttrValue {
        fn to_tokens(&self, tokens: &mut TokenStream) {
            match self {
                Self::LitStr(t) => t.to_tokens(tokens),
                Self::Expr(t) => t.to_tokens(tokens),
                Self::Call(t) => {
                    let t = quote!(#(#t),*);
                    t.to_tokens(tokens)
                }
            }
        }
    }

    #[derive(Copy, Clone, PartialEq, Eq)]
    pub enum AttrKind {
        Clap,
        StructOpt,
        Command,
        Group,
        Arg,
        Value,
    }

    impl AttrKind {
        pub fn as_str(&self) -> &'static str {
            match self {
                Self::Clap => "clap",
                Self::StructOpt => "structopt",
                Self::Command => "command",
                Self::Group => "group",
                Self::Arg => "arg",
                Self::Value => "value",
            }
        }
    }