$0 in extract function assist

[weigangd]

Hello, I am using nvim + LanguageClient-neovim and I have no plugin for snippet support. When I use the "extract function assist" code action, the generated function always has the name $0fun_name. The same happens with nvim-lsp. If I understand #2518 and #4117 correctly, snippet-completion should be disabled automatically if the client does not support snippets.

[Veykril]

Looks like we don't honor the snippet capabilities in that assist https://github.com/rust-analyzer/rust-analyzer/blob/d5b8a401f38f88ecb0d894c88dcbab3d338a0ef2/crates/ide_assists/src/handlers/extract_function.rs#L1071-L1089

[Veykril]

The fix is to check for the capability like done in add_missing_impl_members assist here https://github.com/rust-analyzer/rust-analyzer/blob/d5b8a401f38f88ecb0d894c88dcbab3d338a0ef2/crates/ide_assists/src/handlers/add_missing_impl_members.rs#L121-L140 and add the snippet $0 conditionally.

[tomharmon]

@Veykril you mean like this? That simple? Simply return "" if there isn't that capability, otherwise, do what it already does?

fn format_function(
    ctx: &AssistContext,
    module: hir::Module,
    fun: &Function,
    old_indent: IndentLevel,
    new_indent: IndentLevel,
) -> String {
    let mut fn_def = String::new();

    match ctx.config.snippet_cap {
        None => (),
        Some(_) => {
            let params = make_param_list(ctx, module, fun);
            let ret_ty = make_ret_ty(ctx, module, fun);
            let body = make_body(ctx, old_indent, new_indent, fun);
            format_to!(fn_def, "\n\n{}fn $0{}{}", new_indent, fun.name, params);
            if let Some(ret_ty) = ret_ty {
                format_to!(fn_def, " {}", ret_ty);
            }
            format_to!(fn_def, " {}", body);
        }
    };

    fn_def
}

[Veykril]

No not quite, we still want to emit the code but dont want to emit the $0 snippet parts. The example I linked was for how to check whether we want to emit $0 or not.

[Arthamys]

I've go the changes in my fork, would that be sufficient to close the issue ?

Arthamys@c118f88

edit

Looking in the extract_function() body, I am wondering if https://github.com/rust-analyzer/rust-analyzer/blob/9707acb59b3f1f74bcc2f806ea5eab59279fad5e/crates/ide_assists/src/handlers/extract_function.rs#L115
should also be changed to

match ctx.config.snippet_cap {
                Some(_) => {
                    builder.insert_snippet(ctx.config.snippet_cap.unwrap(), insert_offset, fn_def)
                }
                None => builder.insert(insert_offset, fn_def),
            }

also, or is this not a "snippet insertion" per se ?

[Veykril]

Ye I think that also has to be changed

[bjorn3]

Fixed by #7880.