Add a _nofds helper

Most requests are like this, so let's optimize it a bit and
avoid the callers needing to have `()` spelled out.

Author: cgwalters

src/imageproxy.rs

@@ -444,7 +444,7 @@ impl ImageProxy {
         };
 
         // Verify semantic version
-        let (protover, _): (String, ()) = r.impl_request("Initialize", [(); 0]).await?;
+        let protover: String = r.impl_request_nofds("Initialize", [(); 0]).await?;
         tracing::debug!("Remote protocol version: {protover}");
         let protover = semver::Version::parse(protover.as_str())?;
         // Previously we had a feature to opt-in to requiring newer versions using `if cfg!()`.
@@ -460,6 +460,7 @@ impl ImageProxy {
         Ok(r)
     }
 
+    /// Create and send a request. Should only be used by impl_request.
     async fn impl_request_raw<T: serde::de::DeserializeOwned + Send + 'static, F: FromReplyFds>(
         sockfd: Arc<Mutex<OwnedFd>>,
         req: Request,
@@ -509,6 +510,8 @@ impl ImageProxy {
         Ok(r)
     }
 
+    /// Create a request that may return file descriptors, and also check for an unexpected
+    /// termination of the child process.
     #[instrument(skip(args))]
     async fn impl_request<T: serde::de::DeserializeOwned + Send + 'static, F: FromReplyFds>(
         &self,
@@ -527,6 +530,16 @@ impl ImageProxy {
         }
     }
 
+    /// A synchronous invocation which does not return any file descriptors.
+    async fn impl_request_nofds<T: serde::de::DeserializeOwned + Send + 'static>(
+        &self,
+        method: &str,
+        args: impl IntoIterator<Item = impl Into<serde_json::Value>>,
+    ) -> Result<T> {
+        let (r, ()) = self.impl_request(method, args).await?;
+        Ok(r)
+    }
+
     #[instrument]
     async fn finish_pipe(&self, pipeid: PipeId) -> Result<()> {
         tracing::debug!("closing pipe");
@@ -537,14 +550,16 @@ impl ImageProxy {
     #[instrument]
     pub async fn open_image(&self, imgref: &str) -> Result<OpenedImage> {
         tracing::debug!("opening image");
-        let (imgid, ()) = self.impl_request("OpenImage", [imgref]).await?;
+        let imgid = self.impl_request_nofds("OpenImage", [imgref]).await?;
         Ok(OpenedImage(imgid))
     }
 
     #[instrument]
     pub async fn open_image_optional(&self, imgref: &str) -> Result<Option<OpenedImage>> {
         tracing::debug!("opening image");
-        let (imgid, ()) = self.impl_request("OpenImageOptional", [imgref]).await?;
+        let imgid = self
+            .impl_request_nofds("OpenImageOptional", [imgref])
+            .await?;
         if imgid == 0 {
             Ok(None)
         } else {
@@ -554,9 +569,7 @@ impl ImageProxy {
 
     #[instrument]
     pub async fn close_image(&self, img: &OpenedImage) -> Result<()> {
-        tracing::debug!("closing image");
-        let (r, ()) = self.impl_request("CloseImage", [img.0]).await?;
-        Ok(r)
+        self.impl_request_nofds("CloseImage", [img.0]).await
     }
 
     async fn read_finish_pipe(&self, pipe: FinishPipe) -> Result<Vec<u8>> {
@@ -714,7 +727,7 @@ impl ImageProxy {
         if !layer_info_proto_version().matches(&self.protover) {
             return Ok(None);
         }
-        let (layers, ()) = self.impl_request("GetLayerInfo", [img.0]).await?;
+        let layers = self.impl_request_nofds("GetLayerInfo", [img.0]).await?;
         Ok(Some(layers))
     }