feat(macro): add group macro

examples/group_testing/main.rs

@@ -1,4 +1,4 @@
-use poise::{serenity_prelude as serenity};
+use poise::{serenity_prelude as serenity, Command, CommandGroup};
 use std::{env::var, sync::Arc, time::Duration, vec};
 // Types used by all command functions
 type Error = Box<dyn std::error::Error + Send + Sync>;
@@ -14,7 +14,7 @@ struct Test {}
 impl Test {
     // Just a test
     #[poise::command(slash_command, prefix_command, rename = "test")]
-    async fn aaa(ctx: Context<'_>) -> Result<(), Error> {
+    async fn test_command(ctx: Context<'_>) -> Result<(), Error> {
         let name = ctx.author();
         ctx.say(format!("Hello, {}", name)).await?;
         Ok(())
@@ -39,13 +39,12 @@ async fn on_error(error: poise::FrameworkError<'_, Data, Error>) {
     }
 }
 
-
 #[tokio::main]
 async fn main() {
     // FrameworkOptions contains all of poise's configuration option in one struct
     // Every option can be omitted to use its default value
     // println!("{:#?}", Test::commands());
-    let commands = Test::commands();
+    let commands: Vec<Command<Data, Error>> = Test::commands();
 
     let options = poise::FrameworkOptions {
         commands: commands,
@@ -120,4 +119,3 @@ async fn main() {
 
     client.unwrap().start().await.unwrap()
 }
-

macros/src/lib.rs

@@ -9,6 +9,7 @@ mod util;
 
 use proc_macro::TokenStream;
 use quote::{quote, ToTokens};
+use syn::spanned::Spanned;
 
 /**
 This macro transforms plain functions into poise bot commands.
@@ -336,6 +337,9 @@ fn group_impl(args: TokenStream, input_item: TokenStream) -> Result<TokenStream,
     // collect each ImplItem in a stream
     let mut impl_body = proc_macro2::TokenStream::new();
 
+    // context type for correct type inference in CommandGroup
+    let mut ctx_type_with_static: Option<syn::Type> = None;
+
     for item in item_impl.items.iter() {
         let mut item_stream = quote!(#item);
 
@@ -361,6 +365,26 @@ fn group_impl(args: TokenStream, input_item: TokenStream) -> Result<TokenStream,
                     sig: f.sig.clone(),
                     block: Box::new(f.block.clone()),
                 };
+
+                if let None = ctx_type_with_static {
+                    let context_type = match function.sig.inputs.first() {
+                        Some(syn::FnArg::Typed(syn::PatType { ty, .. })) => Some(&**ty),
+                        _ => {
+                            return Err(syn::Error::new(
+                                function.sig.span(),
+                                "expected a Context parameter",
+                            )
+                            .into())
+                        }
+                    };
+                    // Needed because we're not allowed to have lifetimes in the hacky use case below (in command::mod.rs)
+                    ctx_type_with_static = Some(syn::fold::fold_type(
+                        &mut crate::util::AllLifetimesToStatic,
+                        context_type
+                            .expect("context_type has already been set to Some")
+                            .clone(),
+                    ));
+                }
                 item_stream = command::command(new_args, function)?.into();
             }
         }
@@ -371,8 +395,14 @@ fn group_impl(args: TokenStream, input_item: TokenStream) -> Result<TokenStream,
     }
 
     Ok(quote! {
-        impl<D, E> ::poise::CommandGroup<D, E> for #name {
-            fn commands() -> Vec<::poise::Command<D, E>> {
+        impl ::poise::CommandGroup for #name {
+            type Data = <#ctx_type_with_static as poise::_GetGenerics>::U;
+            type Error = <#ctx_type_with_static as poise::_GetGenerics>::E;
+
+            fn commands() -> Vec<::poise::Command<
+                <#ctx_type_with_static as poise::_GetGenerics>::U,
+                <#ctx_type_with_static as poise::_GetGenerics>::E,
+            >> {
                 vec![#(#name::#command_idents()),*]
             }
         }

src/group.rs

@@ -3,12 +3,12 @@
 /// Trait for a struct with a group of commands.
 ///
 /// You should not implement this yourself, but instead use the `poise::group` macro
-pub trait CommandGroup<D, E> {
-    // /// User data, which is stored and accessible in all command invocations
-    // type Data;
-    // /// The error type of your commands
-    // type Error;
+pub trait CommandGroup {
+    /// User data, which is stored and accessible in all command invocations
+    type Data;
+    /// The error type of your commands
+    type Error;
     /// Return a Vec of the `poise::commands` defined in this group
     /// Automatically generated by the macro
-    fn commands() -> Vec<crate::Command<D, E>>;
+    fn commands() -> Vec<crate::Command<Self::Data, Self::Error>>;
 }