fix(corpus-sweep): name every missing binary, in flag order

Same map-ranging bug as the sibling tool, and this copy had no test on
the missing-binary path at all.

cmd/internal-tools/corpus-sweep/sweep.go

@@ -17,23 +17,31 @@ import (
 // resolveBinaries turns campaign and sanderling into absolute paths before
 // anything is served. Each campaign runs from the sweep's own directory, and a
 // binary that is missing altogether has to stop the sweep here rather than fail
-// once per implementation and seed.
+// once per implementation and seed. Every one that is missing is named
+// together, in flag order: stopping at the first turns that single stop into
+// one rerun per missing binary.
 func resolveBinaries(configuration *config) error {
-	for name, value := range map[string]*string{
-		"--campaign":   &configuration.campaignPath,
-		"--sanderling": &configuration.sanderlingPath,
+	var missing []error
+	for _, binary := range []struct {
+		name  string
+		value *string
+	}{
+		{"--campaign", &configuration.campaignPath},
+		{"--sanderling", &configuration.sanderlingPath},
 	} {
-		resolved, err := exec.LookPath(*value)
+		resolved, err := exec.LookPath(*binary.value)
 		if err != nil {
-			return fmt.Errorf("%s: %w", name, err)
+			missing = append(missing, fmt.Errorf("%s: %w", binary.name, err))
+			continue
 		}
 		absolute, err := filepath.Abs(resolved)
 		if err != nil {
-			return fmt.Errorf("%s: %w", name, err)
+			missing = append(missing, fmt.Errorf("%s: %w", binary.name, err))
+			continue
 		}
-		*value = absolute
+		*binary.value = absolute
 	}
-	return nil
+	return errors.Join(missing...)
 }
 
 type sweep struct {

cmd/internal-tools/corpus-sweep/sweep_test.go

@@ -0,0 +1,46 @@
+package main
+
+import (
+	"path/filepath"
+	"strings"
+	"testing"
+)
+
+// Two binaries missing is one rerun, not two: the operator is told about both
+// at once, in flag order, whatever order the check happened to walk.
+func TestResolveBinaries_NamesEveryMissingBinaryInFlagOrder(t *testing.T) {
+	configuration := config{
+		campaignPath:   "campaign-that-is-not-installed",
+		sanderlingPath: "sanderling-that-is-not-installed",
+	}
+
+	err := resolveBinaries(&configuration)
+	if err == nil {
+		t.Fatal("got no error, want both missing binaries named")
+	}
+	message := err.Error()
+	campaign := strings.Index(message, "--campaign")
+	sanderling := strings.Index(message, "--sanderling")
+	if campaign < 0 || sanderling < 0 {
+		t.Fatalf("got %q, want both --campaign and --sanderling named", message)
+	}
+	if campaign > sanderling {
+		t.Errorf("got %q, want --campaign named before --sanderling", message)
+	}
+
+	resolved := config{
+		campaignPath: writeScript(
+			t,
+			filepath.Join(t.TempDir(), "stub-campaign"),
+			"#!/bin/sh\nexit 0\n",
+		),
+		sanderlingPath: "sanderling-that-is-not-installed",
+	}
+	err = resolveBinaries(&resolved)
+	if err == nil {
+		t.Fatal("got no error, want the missing sanderling named")
+	}
+	if strings.Contains(err.Error(), "--campaign") {
+		t.Errorf("got %q, want the campaign that resolved left out", err.Error())
+	}
+}