Post an error if a given SHA was already benchmarked

site/src/github.rs

@@ -233,12 +233,14 @@ pub async fn rollup_pr_number(
         .then_some(issue.number))
 }
 
-pub async fn enqueue_shas(
+/// Enqueues the given SHAs and returns the SHAs that were actually enqueued.
+pub async fn enqueue_shas<'a>(
     ctxt: &SiteCtxt,
     gh_client: &client::Client,
     pr_number: u32,
-    commits: impl Iterator<Item = &str>,
-) -> Result<(), String> {
+    commits: impl Iterator<Item = &'a str>,
+) -> Result<Vec<&'a str>, String> {
+    let mut enqueued = vec![];
     let mut msg = String::new();
     for commit in commits {
         let mut commit_response = gh_client
@@ -251,7 +253,7 @@ pub async fn enqueue_shas(
                 commit_response.sha,
                 commit_response.parents.len()
             );
-            return Ok(());
+            continue;
         }
         let try_commit = TryCommit {
             sha: commit_response.sha,
@@ -268,6 +270,7 @@ pub async fn enqueue_shas(
             .await
             .map_err(|error| format!("Cannot attach SHAs to try benchmark request on PR {pr_number} and SHA {}: {error:?}", try_commit.sha))?;
         if queued {
+            enqueued.push(commit);
             if !msg.is_empty() {
                 msg.push('\n');
             }
@@ -286,7 +289,7 @@ pub async fn enqueue_shas(
             let queue_msg = format!(
                 r#"There {verb} currently {preceding_artifacts} preceding artifact{suffix} in the [queue](https://perf.rust-lang.org/status.html).
 It will probably take at least ~{:.1} hours until the benchmark run finishes."#,
-                (expected_duration.as_secs_f64() / 3600.0)
+                expected_duration.as_secs_f64() / 3600.0
             );
 
             msg.push_str(&format!(
@@ -303,7 +306,7 @@ It will probably take at least ~{:.1} hours until the benchmark run finishes."#,
         gh_client.post_comment(pr_number, msg).await;
     }
 
-    Ok(())
+    Ok(enqueued)
 }
 
 /// Counts how many artifacts are in the queue before the specified commit, and what is the expected

site/src/request_handlers/github.rs

@@ -284,13 +284,26 @@ async fn handle_rust_timer(
         }
     }
 
-    enqueue_shas(
+    let enqueued = enqueue_shas(
         &ctxt,
         main_client,
         issue.number,
         valid_build_cmds.iter().map(|c| c.sha),
     )
     .await?;
+    if enqueued.len() < valid_build_cmds.len() {
+        use std::fmt::Write;
+
+        let mut msg =
+            "The following SHAs were not enqueued, as they were probably already benchmarked:\n"
+                .to_string();
+        for cmd in valid_build_cmds {
+            if !enqueued.contains(&cmd.sha) {
+                writeln!(msg, "- {}", cmd.sha).unwrap();
+            }
+        }
+        main_client.post_comment(issue.number, msg).await;
+    }
 
     Ok(github::Response)
 }