Rustdoc proc_macro_attribute which adds boilerplate for a doctest

main.rs

/// This struct shows an example
///
/// # Example
#[doc_add_boilerplate(
    /// # // you can use hidden lines
    /// MyStruct::greet(); // this line is visible
)]
struct MyStruct;

proc_macro.rs

#[proc_macro_attribute]
/// Attribute macro which generates a doc test wrapper to reduce boilerplate.
///
/// # Example
///
/// ```rust
///
/// /// Your documentation about the struct
/// /// ...
/// /// # Example
/// #[doc_add_boilerplate(
///  /// MyStruct::may_fail()?;
/// )]
/// struct MyStruct;
/// ```
///
/// This will generate a doc with the following content:
/// ```rust
/// /// Your documentation about the struct
/// /// ...
/// /// # Example
/// /// ```rust
/// /// # #[tokio::main]
/// /// # async fn main() -> Result<(), Box<dyn std::error::Errror + Send + Sync>> {
/// /// MyStruct::may_fail()?;
/// /// # Ok(())
/// /// # }
/// /// ```
pub fn doc_add_boilerplate(attr: TokenStream, input: TokenStream) -> TokenStream {
    let inner: proc_macro2::TokenStream = attr.into();
    let parser = |input: ParseStream<'_>| ::syn::Result::Ok({
        let attrs = Attribute::parse_outer(input)?;
        let rest = input.parse::<TokenStream>().unwrap();
        (attrs, rest)
    });
    let (meta, input) = parse_macro_input!(input with parser);

    quote_spanned!(Span::mixed_site()=>
        #(#meta)*
        /// ```rust
        /// # #[tokio::main]
        /// # async fn main() -> Result<(), Box<dyn std::error::Error + Send + Sync>> {
        #inner
        /// # Ok(())
        /// # }
        /// 
        #input
    ).into()
}