Re: [I] doc: create macros to hide logo/icon [datafusion]

[via GitHub]

mbrobbel commented on issue #14796:
URL: https://github.com/apache/datafusion/issues/14796#issuecomment-2672262000

   > > I looked at this briefly, but couldn't make inner attributes work with a 
proc macro.
   > 
   > HI [@mbrobbel](https://github.com/mbrobbel) do you mean proc macros cannot 
be applied on underlying objects? afaik it is a limited set of object proc 
macros can be applied on like structs, enums, etc
   
   My first attempt was to use a [function-like proc 
macro](https://doc.rust-lang.org/reference/procedural-macros.html#function-like-procedural-macros):
   
   ```rust
   #[proc_macro]
   pub fn doc_cfg(_input: TokenStream) -> TokenStream {
       quote! {
           #![doc(
               
html_logo_url="https://raw.githubusercontent.com/apache/datafusion/19fe44cf2f30cbdd63d4a4f52c74055163c6cc38/docs/logos/standalone_logo/logo_original.svg";,
               
html_favicon_url="https://raw.githubusercontent.com/apache/datafusion/19fe44cf2f30cbdd63d4a4f52c74055163c6cc38/docs/logos/standalone_logo/logo_original.svg";
           )]
           #![cfg_attr(docsrs, feature(doc_auto_cfg))]
       }
       .into()
   }
   ```
   
   This results in:
   ```
   error: an inner attribute is not permitted in this context
     --> datafusion/core/src/lib.rs:19:1
      |
   19 | datafusion_macros::doc_cfg!();
      | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
      |
      = note: inner attributes, like `#![no_std]`, annotate the item enclosing 
them, and are usually found at the beginning of source files
      = note: outer attributes, like `#[test]`, annotate the item following them
      = note: this error originates in the macro `datafusion_macros::doc_cfg` 
(in Nightly builds, run with -Z macro-backtrace for more info)
   
   For more information about this error, try `rustc --explain E0753`.
   ```
   
   The other attempt was to use an [attribute 
macro](https://doc.rust-lang.org/reference/procedural-macros.html#attribute-macros),
 but I don't think attaching this attribute to the `lib.rs` `File` item is 
supported.
   
   Maybe we can use a normal `macro_rules`, but we would need another crate to 
export those.
   
   


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