issue 974: review 2: a check stopped by its key says no verdict, an error judges nothing, and an unacknowledged check goes to a second builder

cmd/mesh-controller/checks.go

@@ -583,6 +583,13 @@ const maxCheckReport = 60 << 10
 // checked says a merge check's verdict as the controller's `checked`. Nothing is recorded or
 // registered: a check builds nothing (issue 240's rule for a dry run, kept for a check).
 func checked(ctx context.Context, result link.BuildResult) {
+	// **A check stopped by its key says nothing** (novox/hq ADR 0406 §4, issue 974, review 2): it stopped because the head or
+	// the trunk commit moved on, and the newer request will judge. Said as an error it would name the live head — red
+	// statuses on the forge, a delivery refused — and written to the key it would stand in the newer request's way.
+	if result.Failed == link.SupersededByKey {
+		fmt.Printf("%s: stopped, its pull request's key moved on; the newer check will judge\n", result.ID)
+		return
+	}
 	sayChecked(ctx, checkedOf(result))
 }
 

cmd/mesh-controller/checks_test.go

@@ -1,9 +1,16 @@
 package main
 
 import (
+	"encoding/json"
 	"errors"
 	"strings"
 	"testing"
+	"time"
+
+	"github.com/nats-io/nats.go"
+
+	"github.com/novox/mesh-controller/internal/broker"
+	"github.com/novox/mesh-controller/internal/testbus"
 
 	"github.com/novox/mesh-controller/internal/inventory"
 	"github.com/novox/mesh-controller/internal/link"
@@ -288,3 +295,47 @@ func TestARecheckedHeadsDirectVerdictNamesItsTrunk(t *testing.T) {
 		t.Fatalf("a rechecked head's direct verdict names trunk %q", c.Trunk)
 	}
 }
+
+// A check stopped by its pull request's key moving on says no verdict (issue 974, review 2): an error said for it would name the
+// live head, and the newer request is the one that judges. A check that failed for any other reason still says its error.
+func TestACheckStoppedByItsKeyIsAnnouncedAsNoVerdict(t *testing.T) {
+	js, err := broker.Dial(testbus.URL(t))
+	if err != nil {
+		t.Fatal(err)
+	}
+	t.Cleanup(js.Close)
+	if err := broker.AssertMeshStreams(js); err != nil {
+		t.Fatal(err)
+	}
+	legacy, err := js.Conn().JetStream()
+	if err != nil {
+		t.Fatal(err)
+	}
+	was := checkEvents
+	checkEvents = link.OverNATS{Conn: js.Conn(), JS: legacy}
+	t.Cleanup(func() { checkEvents = was })
+	heard := make(chan *nats.Msg, 4)
+	sub, err := js.Conn().ChanSubscribe(link.SeatEventSubject(link.MeshControllerSeat, link.KeyChecked), heard)
+	if err != nil {
+		t.Fatal(err)
+	}
+	defer func() { _ = sub.Unsubscribe() }()
+	asked := &link.CheckRequest{Owner: "novox", Repo: "mesh-catalog", Number: 3}
+	checked(t.Context(), link.BuildResult{ID: "stopped", Ref: "abc", Checked: asked, Failed: link.SupersededByKey})
+	checked(t.Context(), link.BuildResult{ID: "broken", Ref: "abc", Checked: asked, Failed: "the facts snapshot cannot be read"})
+	select {
+	case m := <-heard:
+		var c link.Checked
+		_ = json.Unmarshal(m.Data, &c)
+		if c.ID != "broken" || c.Verdict != "error" {
+			t.Fatalf("the first verdict said is %+v; want only the broken check's error", c)
+		}
+	case <-time.After(5 * time.Second):
+		t.Fatal("nothing was said")
+	}
+	select {
+	case m := <-heard:
+		t.Fatalf("a second verdict was said: %s", m.Data)
+	case <-time.After(300 * time.Millisecond):
+	}
+}