[dropshot_endpoint] support raw identifiers as API trait method names

CHANGELOG.adoc

@@ -16,6 +16,7 @@
 https://github.com/oxidecomputer/dropshot/compare/v0.17.1\...HEAD[Full list of commits]
 
 * The minimum supported Rust version is now 1.88.
+* Endpoint and channel methods within API traits can now have raw identifier names (such as `r#async`). Previously this caused a proc-macro panic.
 
 == 0.17.1 (released 2026-06-02)
 

dropshot/tests/integration-tests/api_trait.rs

@@ -108,6 +108,56 @@ async fn test_api_trait_basic() {
     testctx.teardown().await;
 }
 
+// The trait is allowed to have raw identifiers.
+#[dropshot::api_description { context = "r#type", module = "r#mod" }]
+#[allow(non_camel_case_types)]
+trait RawIdentApi {
+    type r#type;
+
+    #[endpoint { method = GET, path = "/async" }]
+    async fn r#async(
+        _rqctx: RequestContext<Self::r#type>,
+    ) -> Result<HttpResponseUpdatedNoContent, HttpError>;
+
+    #[channel { protocol = WEBSOCKETS, path = "/await" }]
+    async fn r#await(
+        _rqctx: RequestContext<Self::r#type>,
+        _upgraded: dropshot::WebsocketConnection,
+    ) -> dropshot::WebsocketChannelResult;
+}
+
+enum RawIdentImpl {}
+
+impl RawIdentApi for RawIdentImpl {
+    type r#type = ();
+
+    async fn r#async(
+        _rqctx: RequestContext<Self::r#type>,
+    ) -> Result<HttpResponseUpdatedNoContent, HttpError> {
+        Ok(HttpResponseUpdatedNoContent())
+    }
+
+    async fn r#await(
+        _rqctx: RequestContext<Self::r#type>,
+        _upgraded: dropshot::WebsocketConnection,
+    ) -> dropshot::WebsocketChannelResult {
+        Ok(())
+    }
+}
+
+#[test]
+fn test_api_trait_raw_idents() {
+    r#mod::stub_api_description().unwrap();
+
+    let api = r#mod::api_description::<RawIdentImpl>().unwrap();
+    let spec = api
+        .openapi("Raw identifiers", semver::Version::new(1, 0, 0))
+        .json()
+        .unwrap();
+    assert!(spec["paths"]["/async"]["get"].is_object(), "{spec:#}");
+    assert!(spec["paths"]["/await"]["get"].is_object(), "{spec:#}");
+}
+
 #[dropshot::api_description {
     tag_config = {
         tags = {},

dropshot_endpoint/src/api_trait.rs

@@ -1387,7 +1387,7 @@ impl<'ast> ApiEndpoint<'ast> {
         //
         // Note that there isn't any possible variable name collision here,
         // since all names are prefixed with "endpoint_".
-        let endpoint_name = format_ident!("endpoint_{}", name_str);
+        let endpoint_name = endpoint_var_name(&name_str);
 
         quote_spanned! {self.attr.span()=>
             {
@@ -1400,6 +1400,14 @@ impl<'ast> ApiEndpoint<'ast> {
     }
 }
 
+/// Returns the name of the local variable holding an endpoint's `ApiEndpoint`.
+///
+/// Raw identifiers must have their `r#` prefix stripped (`format_ident!` only
+/// does this for `syn::Ident`, not for strings).
+fn endpoint_var_name(name_str: &str) -> syn::Ident {
+    format_ident!("endpoint_{}", name_str.trim_start_matches("r#"))
+}
+
 fn parse_channel_metadata(
     name_str: &str,
     attr: &syn::Attribute,
@@ -1550,7 +1558,7 @@ impl<'ast> ApiChannel<'ast> {
         //
         // Note that there isn't any possible variable name collision here,
         // since all names are prefixed with "endpoint_".
-        let endpoint_name = format_ident!("endpoint_{}", name_str);
+        let endpoint_name = endpoint_var_name(&name_str);
 
         quote_spanned! {self.attr.span()=>
             {
@@ -1695,7 +1703,10 @@ impl StripRecognizedAttrs for Vec<syn::Attribute> {
 mod tests {
     use expectorate::assert_contents;
 
-    use crate::{test_util::assert_banned_idents, util::DROPSHOT};
+    use crate::{
+        test_util::{assert_banned_idents, find_idents},
+        util::DROPSHOT,
+    };
 
     use super::*;
 
@@ -1818,6 +1829,32 @@ mod tests {
         );
     }
 
+    /// Raw identifiers are valid.
+    #[test]
+    fn test_api_trait_raw_idents() {
+        let (item, errors) = do_trait(
+            quote! { context = "r#type", module = "r#mod" },
+            quote! {
+                trait r#trait {
+                    type r#type;
+
+                    #[endpoint { method = GET, path = "/async" }]
+                    async fn r#async(
+                        rqctx: RequestContext<Self::r#type>,
+                    ) -> Result<HttpResponseOk<()>, HttpError>;
+                }
+            },
+        );
+
+        assert!(errors.is_empty(), "no errors: {errors:#?}");
+        let file: syn::File = parse_quote! { #item };
+        let found = find_idents(&file, ["r#mod", "r#type", "endpoint_async"]);
+        assert_eq!(
+            found.into_iter().collect::<Vec<_>>(),
+            ["endpoint_async", "r#mod", "r#type"]
+        );
+    }
+
     #[test]
     fn test_api_trait_operation_id() {
         let (item, errors) = do_trait(