Print warning when assigning someone on vacation

People on vacation will usually not (they better >:() respond during
their vacation, but they probably will be able to respond after. There
is no reason why you wouldn't be able to assign to someone on vacation
manually if this person is the best reviewer and you have enough
patience for them to return, so don't prevent it. Do print a warning
though to set expectations for both the author and triage.

Author: Noratrieb

src/handlers/assign.rs

@@ -72,7 +72,7 @@ const RETURNING_USER_WELCOME_MESSAGE_NO_REVIEWER: &str =
 
 const ON_VACATION_WARNING: &str = "{username} is on vacation.
 
-Please choose another assignee.";
+They may take a while to respond.";
 
 const NON_DEFAULT_BRANCH: &str =
     "Pull requests are usually filed against the {default} branch for this repo, \
@@ -342,7 +342,8 @@ async fn determine_assignee(
             return Ok((Some(name.to_string()), true));
         }
         // User included `r?` in the opening PR body.
-        match find_reviewer_from_names(&db_client, &teams, config, &event.issue, &[name]).await {
+        match find_reviewer_from_names(&db_client, &teams, config, &event.issue, ctx, &[name]).await
+        {
             Ok(assignee) => return Ok((Some(assignee), true)),
             Err(e) => {
                 event
@@ -356,8 +357,15 @@ async fn determine_assignee(
     // Errors fall-through to try fallback group.
     match find_reviewers_from_diff(config, diff) {
         Ok(candidates) if !candidates.is_empty() => {
-            match find_reviewer_from_names(&db_client, &teams, config, &event.issue, &candidates)
-                .await
+            match find_reviewer_from_names(
+                &db_client,
+                &teams,
+                config,
+                &event.issue,
+                ctx,
+                &candidates,
+            )
+            .await
             {
                 Ok(assignee) => return Ok((Some(assignee), false)),
                 Err(FindReviewerError::TeamNotFound(team)) => log::warn!(
@@ -396,7 +404,9 @@ async fn determine_assignee(
     }
 
     if let Some(fallback) = config.adhoc_groups.get("fallback") {
-        match find_reviewer_from_names(&db_client, &teams, config, &event.issue, fallback).await {
+        match find_reviewer_from_names(&db_client, &teams, config, &event.issue, ctx, fallback)
+            .await
+        {
             Ok(assignee) => return Ok((Some(assignee), false)),
             Err(e) => {
                 log::trace!(
@@ -507,6 +517,10 @@ pub(super) async fn handle_command(
     // posts contain commands to instruct the user, not things that the bot
     // should respond to.
     if event.user().login == ctx.username.as_str() {
+        tracing::debug!(
+            "Received command from {}, which is the bot itself, ignoring",
+            ctx.username.as_str()
+        );
         return Ok(());
     }
 
@@ -605,6 +619,7 @@ pub(super) async fn handle_command(
                         &teams,
                         config,
                         issue,
+                        ctx,
                         &[team_name.to_string()],
                     )
                     .await
@@ -809,6 +824,7 @@ async fn find_reviewer_from_names(
     teams: &Teams,
     config: &AssignConfig,
     issue: &Issue,
+    ctx: &Context,
     names: &[String],
 ) -> Result<String, FindReviewerError> {
     let candidates = candidate_reviewers_from_names(teams, config, issue, names)?;
@@ -843,6 +859,24 @@ async fn find_reviewer_from_names(
         return Ok("ghost".to_string());
     }
 
+    let pick = candidates
+        .into_iter()
+        .choose(&mut rand::thread_rng())
+        .expect("candidate_reviewers_from_names should return at least one entry")
+        .to_string();
+
+    if config.is_on_vacation(&pick) {
+        let result = issue
+            .post_comment(
+                &ctx.github,
+                &ON_VACATION_WARNING.replace("{username}", &pick),
+            )
+            .await;
+        if let Err(err) = result {
+            tracing::error!(?err, "Failed to post vacation warning");
+        }
+    }
+
     // filter out team members without capacity
     // let filtered_candidates = filter_by_capacity(db, &candidates)
     //     .await
@@ -864,11 +898,7 @@ async fn find_reviewer_from_names(
     // );
 
     // Return unfiltered list of candidates
-    Ok(candidates
-        .into_iter()
-        .choose(&mut rand::thread_rng())
-        .expect("candidate_reviewers_from_names should return at least one entry")
-        .to_string())
+    Ok(pick)
 }
 
 /// Returns a list of candidate usernames (from relevant teams) to choose as a reviewer.