huskies: merge 1077

server/src/service/notifications/format.rs

@@ -240,21 +240,28 @@ pub fn format_new_item_notification(
     (plain, html)
 }
 
-/// Extract the first non-empty line from a merge failure reason, truncated to `max_len` chars.
+/// Maximum number of trailing gate-output lines included in a merge-failure
+/// chat notification.
 ///
-/// Used to produce a compact snippet for chat notifications.
-pub fn merge_failure_snippet(reason: &str, max_len: usize) -> String {
-    let line = reason
-        .lines()
-        .find(|l| !l.trim().is_empty())
-        .unwrap_or(reason);
-    let mut chars = line.chars();
-    let truncated: String = chars.by_ref().take(max_len).collect();
-    if chars.next().is_some() {
-        format!("{truncated}\u{2026}") // append …
-    } else {
-        truncated
+/// Gate output can be hundreds of lines; only the tail (where errors appear)
+/// is useful at a glance.  Full output remains available via `get_merge_status`
+/// or the web UI — this limit is chat-display-only.
+pub const MERGE_FAILURE_TAIL_LINES: usize = 30;
+
+/// Truncate `gate_output` to its last `max_lines` lines for chat notifications.
+///
+/// If the output contains more than `max_lines` non-empty lines, a leading
+/// marker line `[...output truncated, last N lines shown...]` is prepended to
+/// the tail so readers know output was cut.  If the output fits within the
+/// limit it is returned unchanged (no marker added).
+pub fn truncate_gate_output(gate_output: &str, max_lines: usize) -> String {
+    let lines: Vec<&str> = gate_output.lines().collect();
+    if lines.len() <= max_lines {
+        return gate_output.to_string();
     }
+    let tail = &lines[lines.len() - max_lines..];
+    let marker = format!("[...output truncated, last {max_lines} lines shown...]");
+    format!("{marker}\n{}", tail.join("\n"))
 }
 
 #[cfg(test)]
@@ -588,6 +595,64 @@ mod tests {
         assert_eq!(plain, "\u{1F916} #42 \u{2014} coder-1 started");
     }
 
+    // ── truncate_gate_output ──────────────────────────────────────────────────
+
+    #[test]
+    fn truncate_gate_output_short_output_returned_unchanged() {
+        let output = "line1\nline2\nline3";
+        assert_eq!(truncate_gate_output(output, 30), output);
+    }
+
+    #[test]
+    fn truncate_gate_output_exact_limit_returned_unchanged() {
+        let lines: Vec<String> = (1..=30).map(|i| format!("line{i}")).collect();
+        let output = lines.join("\n");
+        assert_eq!(truncate_gate_output(&output, 30), output);
+    }
+
+    #[test]
+    fn truncate_gate_output_over_limit_prepends_marker() {
+        let lines: Vec<String> = (1..=35).map(|i| format!("line{i}")).collect();
+        let output = lines.join("\n");
+        let result = truncate_gate_output(&output, 30);
+        assert!(
+            result.starts_with("[...output truncated, last 30 lines shown...]"),
+            "must start with truncation marker; got: {result}"
+        );
+    }
+
+    #[test]
+    fn truncate_gate_output_over_limit_contains_tail_lines() {
+        let lines: Vec<String> = (1..=35).map(|i| format!("line{i}")).collect();
+        let output = lines.join("\n");
+        let result = truncate_gate_output(&output, 30);
+        // Last 30 lines are line6..line35.
+        assert!(result.contains("line35"), "must contain last line");
+        assert!(result.contains("line6"), "must contain first tail line");
+        assert!(!result.contains("line5"), "must not contain dropped line");
+    }
+
+    #[test]
+    fn truncate_gate_output_empty_input_returned_unchanged() {
+        assert_eq!(truncate_gate_output("", 30), "");
+    }
+
+    #[test]
+    fn truncate_gate_output_single_line_returned_unchanged() {
+        assert_eq!(truncate_gate_output("only one line", 30), "only one line");
+    }
+
+    #[test]
+    fn truncate_gate_output_marker_contains_configured_limit() {
+        let lines: Vec<String> = (1..=10).map(|i| format!("x{i}")).collect();
+        let output = lines.join("\n");
+        let result = truncate_gate_output(&output, 5);
+        assert!(
+            result.contains("last 5 lines shown"),
+            "marker must state configured limit; got: {result}"
+        );
+    }
+
     // ── format_agent_completed_notification ───────────────────────────────────
 
     #[test]

server/src/service/notifications/io/listener.rs

@@ -14,10 +14,10 @@ use tokio::sync::broadcast;
 use super::super::events::classify;
 use super::super::filter::{AGENT_EVENT_DEBOUNCE, should_send_rate_limit};
 use super::super::format::{
-    format_agent_completed_notification, format_agent_started_notification,
-    format_blocked_notification, format_error_notification, format_new_item_notification,
-    format_oauth_account_swapped, format_oauth_accounts_exhausted, format_rate_limit_notification,
-    merge_failure_snippet,
+    MERGE_FAILURE_TAIL_LINES, format_agent_completed_notification,
+    format_agent_started_notification, format_blocked_notification, format_error_notification,
+    format_new_item_notification, format_oauth_account_swapped, format_oauth_accounts_exhausted,
+    format_rate_limit_notification, truncate_gate_output,
 };
 use super::super::route::rooms_for_notification;
 use super::{find_story_name_any_stage, read_story_name};
@@ -120,9 +120,7 @@ pub fn spawn_notification_listener(
                         continue;
                     };
                     let story_name = read_story_name(&project_root, "4_merge", story_id);
-                    // AC3: include only the first non-empty line of the failure,
-                    // truncated to ~120 chars.
-                    let snippet = merge_failure_snippet(reason, 120);
+                    let snippet = truncate_gate_output(reason, MERGE_FAILURE_TAIL_LINES);
                     let (plain, html) = format_error_notification(story_id, &story_name, &snippet);
                     slog!("[bot] Sending error notification: {plain}");
                     for room_id in &rooms_for_notification(&get_room_ids) {

server/src/service/notifications/io/tests_notifications.rs

@@ -5,6 +5,89 @@ use super::spawn_notification_listener;
 use crate::io::watcher::WatcherEvent;
 use tokio::sync::broadcast;
 
+// ── spawn_notification_listener: MergeFailure ────────────────────────────────
+
+/// Long gate output is truncated to the tail and includes the marker line.
+#[tokio::test]
+async fn merge_failure_long_output_is_truncated_to_tail() {
+    let tmp = tempfile::tempdir().unwrap();
+    let (watcher_tx, watcher_rx) = broadcast::channel::<WatcherEvent>(16);
+    let (transport, calls) = MockTransport::new();
+
+    spawn_notification_listener(
+        transport,
+        || vec!["!room1:example.org".to_string()],
+        watcher_rx,
+        tmp.path().to_path_buf(),
+    );
+
+    // Build a reason with 50 lines (more than MERGE_FAILURE_TAIL_LINES = 30).
+    let long_reason: String = (1..=50).map(|i| format!("gate-line-{i}\n")).collect();
+
+    watcher_tx
+        .send(WatcherEvent::MergeFailure {
+            story_id: "1077_story_trunc".to_string(),
+            reason: long_reason,
+        })
+        .unwrap();
+
+    tokio::time::sleep(std::time::Duration::from_millis(100)).await;
+
+    let calls = calls.lock().unwrap();
+    assert_eq!(calls.len(), 1, "Expected exactly one notification");
+    let (_, plain, _) = &calls[0];
+    assert!(
+        plain.contains("truncated"),
+        "notification must contain the truncation marker; got: {plain}"
+    );
+    assert!(
+        plain.contains("gate-line-50"),
+        "notification must contain the last line; got: {plain}"
+    );
+    assert!(
+        !plain.contains("gate-line-1\n"),
+        "notification must not contain the first (dropped) line; got: {plain}"
+    );
+}
+
+/// Short gate output (within limit) passes through unchanged, no marker added.
+#[tokio::test]
+async fn merge_failure_short_output_passes_through_unchanged() {
+    let tmp = tempfile::tempdir().unwrap();
+    let (watcher_tx, watcher_rx) = broadcast::channel::<WatcherEvent>(16);
+    let (transport, calls) = MockTransport::new();
+
+    spawn_notification_listener(
+        transport,
+        || vec!["!room1:example.org".to_string()],
+        watcher_rx,
+        tmp.path().to_path_buf(),
+    );
+
+    let short_reason = "error: type mismatch on line 42\nexpected i32, found &str".to_string();
+
+    watcher_tx
+        .send(WatcherEvent::MergeFailure {
+            story_id: "1077_story_short".to_string(),
+            reason: short_reason.clone(),
+        })
+        .unwrap();
+
+    tokio::time::sleep(std::time::Duration::from_millis(100)).await;
+
+    let calls = calls.lock().unwrap();
+    assert_eq!(calls.len(), 1, "Expected exactly one notification");
+    let (_, plain, _) = &calls[0];
+    assert!(
+        !plain.contains("truncated"),
+        "short output must not have a truncation marker; got: {plain}"
+    );
+    assert!(
+        plain.contains("type mismatch"),
+        "short output must be included verbatim; got: {plain}"
+    );
+}
+
 // ── spawn_notification_listener: RateLimitWarning ────────────────────────────
 
 /// AC2 + AC3: when a RateLimitWarning event arrives, send_message is called