1 files changed, 43 insertions, 5 deletions

diff --git a/embassy-executor-macros/src/macros/main.rs b/embassy-executor-macros/src/macros/main.rs
index 24f61f30b..95722b19b 100644
--- a/embassy-executor-macros/src/macros/main.rs
+++ b/embassy-executor-macros/src/macros/main.rs
@@ -16,42 +16,57 @@ enum Flavor {
 pub(crate) struct Arch {
     default_entry: Option<&'static str>,
     flavor: Flavor,
+    executor_required: bool,
 }
 
 pub static ARCH_AVR: Arch = Arch {
     default_entry: Some("avr_device::entry"),
     flavor: Flavor::Standard,
+    executor_required: false,
 };
 
 pub static ARCH_RISCV: Arch = Arch {
     default_entry: Some("riscv_rt::entry"),
     flavor: Flavor::Standard,
+    executor_required: false,
 };
 
 pub static ARCH_CORTEX_M: Arch = Arch {
     default_entry: Some("cortex_m_rt::entry"),
     flavor: Flavor::Standard,
+    executor_required: false,
 };
 
 pub static ARCH_SPIN: Arch = Arch {
     default_entry: None,
     flavor: Flavor::Standard,
+    executor_required: false,
 };
 
 pub static ARCH_STD: Arch = Arch {
     default_entry: None,
     flavor: Flavor::Standard,
+    executor_required: false,
 };
 
 pub static ARCH_WASM: Arch = Arch {
     default_entry: Some("wasm_bindgen::prelude::wasm_bindgen(start)"),
     flavor: Flavor::Wasm,
+    executor_required: false,
+};
+
+pub static ARCH_UNSPECIFIED: Arch = Arch {
+    default_entry: None,
+    flavor: Flavor::Standard,
+    executor_required: true,
 };
 
 #[derive(Debug, FromMeta, Default)]
 struct Args {
     #[darling(default)]
     entry: Option<String>,
+    #[darling(default)]
+    executor: Option<String>,
 }
 
 pub fn run(args: TokenStream, item: TokenStream, arch: &Arch) -> TokenStream {
@@ -112,9 +127,10 @@ pub fn run(args: TokenStream, item: TokenStream, arch: &Arch) -> TokenStream {
         error(&mut errors, &f.sig, "main function must have 1 argument: the spawner.");
     }
 
-    let entry = match args.entry.as_deref().or(arch.default_entry) {
-        None => TokenStream::new(),
-        Some(x) => match TokenStream::from_str(x) {
+    let entry = match (args.entry.as_deref(), arch.default_entry.as_deref()) {
+        (None, None) => TokenStream::new(),
+        (Some(x), _) | (None, Some(x)) if x == "" => TokenStream::new(),
+        (Some(x), _) | (None, Some(x)) => match TokenStream::from_str(x) {
             Ok(x) => quote!(#[#x]),
             Err(e) => {
                 error(&mut errors, &f.sig, e);
@@ -123,6 +139,28 @@ pub fn run(args: TokenStream, item: TokenStream, arch: &Arch) -> TokenStream {
         },
     };
 
+    let executor = match (args.executor.as_deref(), arch.executor_required) {
+        (None, true) => {
+            error(
+                &mut errors,
+                &f.sig,
+                "\
+No architecture selected for embassy-executor. Make sure you've enabled one of the `arch-*` features in your Cargo.toml.
+
+Alternatively, if you would like to use a custom executor implementation, specify it with the `executor` argument.
+For example: `#[embassy_executor::main(entry = ..., executor = \"some_crate::Executor\")]",
+            );
+            ""
+        }
+        (Some(x), _) => x,
+        (None, _) => "::embassy_executor::Executor",
+    };
+
+    let executor = TokenStream::from_str(executor).unwrap_or_else(|e| {
+        error(&mut errors, &f.sig, e);
+        TokenStream::new()
+    });
+
     let f_body = f.body;
     let out = &f.sig.output;
 
@@ -134,7 +172,7 @@ pub fn run(args: TokenStream, item: TokenStream, arch: &Arch) -> TokenStream {
                     ::core::mem::transmute(t)
                 }
 
-                let mut executor = ::embassy_executor::Executor::new();
+                let mut executor = #executor::new();
                 let executor = unsafe { __make_static(&mut executor) };
                 executor.run(|spawner| {
                     spawner.must_spawn(__embassy_main(spawner));
@@ -144,7 +182,7 @@ pub fn run(args: TokenStream, item: TokenStream, arch: &Arch) -> TokenStream {
         Flavor::Wasm => (
             quote!(Result<(), wasm_bindgen::JsValue>),
             quote! {
-                let executor = ::std::boxed::Box::leak(::std::boxed::Box::new(::embassy_executor::Executor::new()));
+                let executor = ::std::boxed::Box::leak(::std::boxed::Box::new(#executor::new()));
 
                 executor.start(|spawner| {
                     spawner.must_spawn(__embassy_main(spawner));