Test procmacros (#4372)

* Make the procmacros unit testable

* Apply Clippy suggestion

* unwrap less

* Test (at least) the happy path for most procmacros

* Increase coverage

* More coverage

* Address review comments

Author: bjoernQ

esp-hal-procmacros/Cargo.toml

@@ -8,6 +8,8 @@ documentation = "https://docs.espressif.com/projects/rust/esp-hal-procmacros/lat
 repository    = "https://github.com/esp-rs/esp-hal"
 license       = "MIT OR Apache-2.0"
 
+exclude = ["testdata"]
+
 [package.metadata.espressif]
 doc-config = { features = [] }
 check-configs = [

esp-hal-procmacros/src/blocking.rs

@@ -1,30 +1,24 @@
 #![deny(warnings)]
 
-use proc_macro::TokenStream;
-use proc_macro2::Span;
+use proc_macro2::{Span, TokenStream};
 use syn::{
     ItemFn,
     parse::{self},
-    parse_macro_input,
 };
 
 /// Marks the firmware entry point.
-pub fn main(args: TokenStream, input: TokenStream) -> TokenStream {
-    let f = parse_macro_input!(input as ItemFn);
-
+pub fn main(args: TokenStream, f: ItemFn) -> TokenStream {
     if f.sig.asyncness.is_some() {
         return parse::Error::new(
             Span::call_site(),
             "If you want to use `async` please use `esp-rtos`'s `#[esp_rtos::main]` macro instead.",
         )
-        .to_compile_error()
-        .into();
+        .to_compile_error();
     }
 
     if !args.is_empty() {
         return parse::Error::new(Span::call_site(), "This attribute accepts no arguments")
-            .to_compile_error()
-            .into();
+            .to_compile_error();
     }
 
     let root = match proc_macro_crate::crate_name("esp-hal") {
@@ -37,5 +31,68 @@ pub fn main(args: TokenStream, input: TokenStream) -> TokenStream {
         #[#root::__macro_implementation::__entry]
         #f
     )
-    .into()
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_basic() {
+        let result = main(
+            quote::quote! {}.into(),
+            syn::parse2(quote::quote! {
+                fn main() {}
+            })
+            .unwrap(),
+        );
+
+        assert_eq!(
+            result.to_string(),
+            quote::quote! {
+                #[doc = "The main entry point of the firmware, generated by the `#[main]` macro."]
+                #[esp_hal::__macro_implementation::__entry]
+                fn main () { }
+            }
+            .to_string()
+        );
+    }
+
+    #[test]
+    fn test_try_async() {
+        let result = main(
+            quote::quote! {}.into(),
+            syn::parse2(quote::quote! {
+                async fn main() {}
+            })
+            .unwrap(),
+        );
+
+        assert_eq!(
+            result.to_string(),
+            quote::quote! {
+                ::core::compile_error!{ "If you want to use `async` please use `esp-rtos`'s `#[esp_rtos::main]` macro instead." }
+            }
+            .to_string()
+        );
+    }
+
+    #[test]
+    fn test_try_non_emptyargs() {
+        let result = main(
+            quote::quote! {non_empty}.into(),
+            syn::parse2(quote::quote! {
+                fn main() {}
+            })
+            .unwrap(),
+        );
+
+        assert_eq!(
+            result.to_string(),
+            quote::quote! {
+                ::core::compile_error!{ "This attribute accepts no arguments" }
+            }
+            .to_string()
+        );
+    }
 }