server: avoid skipping builds if we can't fetch them

Due to GitHub API inconsistencies, it might happen that fetching the
build from the API the first time fails. This will return an error,
causing a return before the ID could be removed from the "seen" list.

This fixes the problem by moving adding a crate to the "seen" list after
such requests.

Author: pietroalbini

src/bin/server/worker.rs

@@ -126,11 +126,6 @@ impl Worker {
             info!("build {}: ignoring recently seen id", build_id);
             return Ok(());
         }
-        self.seen.push_front(build_id);
-        if self.seen.len() > KEEP_IDS {
-            self.seen.pop_back();
-        }
-
         let query_from = if self.query_builds_from_primary_repo {
             &self.repo
         } else {
@@ -145,18 +140,20 @@ impl Worker {
 
         debug!("build {}: current outcome: {:?}", build_id, outcome);
         debug!("build {}: PR number: {:?}", build_id, build.pr_number());
-        debug!("build {}: branch name: {:?}", build_id, build.pr_number(),);
+        debug!("build {}: branch name: {:?}", build_id, build.pr_number());
 
         if !outcome.is_finished() {
             info!("build {}: ignoring in-progress build", build_id);
-            if let Some(idx) = self.seen.iter().position(|id| *id == build_id) {
-                // Remove ignored builds, as we haven't reported anything for them and the
-                // in-progress status might be misleading (e.g., leading edge of a group of
-                // notifications).
-                self.seen.remove(idx);
-            }
             return Ok(());
         }
+
+        // Avoid processing the same build multiple times.
+        info!("build {}: marked as seen", build_id);
+        self.seen.push_front(build_id);
+        if self.seen.len() > KEEP_IDS {
+            self.seen.pop_back();
+        }
+
         if !outcome.is_passed() {
             info!("build {}: preparing report", build_id);
             self.report_failed(build.as_ref())?;