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//! Extension traits for [`syn`]
use sealed::sealed;
use syn::parse::{Parse, ParseBuffer, ParseStream};
use syn::LitBool;
use crate::{DelimitedIter, ValueSyntax};
/// [`ParseBuffer`] extensions
#[sealed]
pub trait ParseBufferExt {
/// Parse a boolean attribute
///
/// | Value | Result |
/// | ----------------- | ------- |
/// | `my_attr` | `true` |
/// | `my_attr(true)` | `true` |
/// | `my_attr(false)` | `false` |
/// | `my_attr = true` | `true` |
/// | `my_attr = false` | `false` |
///
/// # Examples
///
/// ```
/// # use macroific_attr_parse::__attr_parse_prelude::*;
/// # use syn::parse::{Parse, ParseStream};
/// # use proc_macro2::TokenStream;
/// # use quote::quote;
/// #
/// struct MyStruct(bool);
/// impl Parse for MyStruct {
/// fn parse(input: ParseStream) -> syn::Result<Self> {
/// input.parse_bool_attr().map(Self)
/// }
/// }
///
/// fn check(expect: bool, tokens: TokenStream) {
/// let tokens_str = tokens.to_string();
/// match syn::parse2::<MyStruct>(tokens) {
/// Ok(MyStruct(actual)) => assert_eq!(actual, expect, "parsed value mismatch"),
/// Err(e) => panic!("Error parsing `{tokens_str}`: {e}")
/// }
/// }
///
/// check(true, TokenStream::new());
/// check(true, quote!((true)));
/// check(false, quote!((false)));
/// check(true, quote!(= true));
/// check(false, quote!(= false));
/// ```
fn parse_bool_attr(&self) -> syn::Result<bool>;
/// Parse a valued attribute
///
/// | Value | Result |
/// | --------------------- | --------------------- |
/// | `my_attr(something)` | `P::parse(something)` |
/// | `my_attr = something` | `P::parse(something)` |
///
/// The `my_attr(something)` syntax should be preferred as `my_attr = something` can't always
/// deserialise some types (e.g. [`Visibility`](syn::Visibility)).
///
/// # Example
///
/// ```
/// # use macroific_attr_parse::__attr_parse_prelude::*;
/// # use proc_macro2::Ident;
/// # use syn::parse_quote;
/// # use syn::parse::{Parse, ParseStream};
/// #
/// struct MyStruct(Ident);
/// impl Parse for MyStruct {
/// fn parse(input: ParseStream) -> syn::Result<Self> {
/// input.parse_valued_attr().map(Self)
/// }
/// }
///
/// let v: MyStruct = parse_quote!((foo));
/// assert_eq!(v.0, "foo");
///
/// let v: MyStruct = parse_quote!(= bar);
/// assert_eq!(v.0, "bar");
/// ```
fn parse_valued_attr<P: Parse>(&self) -> syn::Result<P>;
/// Shortcut for [`DelimitedIter::new`]
fn iter_delimited<T, D>(&self) -> DelimitedIter<'_, T, D>
where
T: Parse,
D: Parse;
}
#[sealed]
impl ParseBufferExt for ParseBuffer<'_> {
fn parse_bool_attr(&self) -> syn::Result<bool> {
Ok(if let Some(syntax) = ValueSyntax::from_stream(self) {
syntax.parse::<LitBool>(self)?.value
} else {
true
})
}
fn parse_valued_attr<P: Parse>(&self) -> syn::Result<P> {
ValueSyntax::from_stream(self).and_parse(self)
}
fn iter_delimited<T, D>(&self) -> DelimitedIter<'_, T, D>
where
T: Parse,
D: Parse,
{
DelimitedIter::new(self)
}
}
/// [`Option`] extensions
#[sealed]
pub trait OptionExt {
/// If the `Option<ValueSyntax>` is `Some`, parse it based on the [`ValueSyntax`],
/// otherwise just parse it.
///
/// # Example
///
/// ```
/// # use macroific_attr_parse::__attr_parse_prelude::*;
/// # use macroific_attr_parse::ValueSyntax;
/// # use syn::parse_quote;
/// # use syn::parse::{Parse, ParseStream};
/// # use proc_macro2::Ident;
/// #
/// struct MyStruct(Ident);
/// impl Parse for MyStruct {
/// fn parse(input: ParseStream) -> syn::Result<Self> {
/// ValueSyntax::from_stream(input).and_parse(input).map(Self)
/// }
/// }
///
/// let v: MyStruct = parse_quote!(foo);
/// assert_eq!(v.0, "foo");
///
/// let v: MyStruct = parse_quote!(= bar);
/// assert_eq!(v.0, "bar");
///
/// let v: MyStruct = parse_quote!((qux));
/// assert_eq!(v.0, "qux");
/// ```
fn and_parse<P: Parse>(self, input: ParseStream) -> syn::Result<P>;
}
#[sealed]
impl OptionExt for Option<ValueSyntax> {
fn and_parse<P: Parse>(self, input: ParseStream) -> syn::Result<P> {
if let Some(syntax) = self {
syntax.parse(input)
} else {
input.parse()
}
}
}