Reject special files before preparing inputs

internal/app/operator_inspection.go

@@ -276,8 +276,8 @@ func requireInspectionFile(path, label string) error {
 		}
 		return fmt.Errorf("stat %s %q: %w", label, path, err)
 	}
-	if info.IsDir() {
-		return fmt.Errorf("%s %q is a directory", label, path)
+	if !info.Mode().IsRegular() {
+		return fmt.Errorf("%s %q is not a regular file", label, path)
 	}
 	return nil
 }

internal/app/operator_inspection_fifo_test.go

@@ -0,0 +1,34 @@
+//go:build unix
+
+package app
+
+import (
+	"path/filepath"
+	"strings"
+	"testing"
+
+	"gitea.maximumdirect.net/eric/narratio/internal/config"
+	"golang.org/x/sys/unix"
+)
+
+func TestInspectStableInputsRejectsSpellCatalogFIFO(t *testing.T) {
+	root := t.TempDir()
+	sourcePath := filepath.Join(root, "spells.fifo")
+	if err := unix.Mkfifo(sourcePath, 0o644); err != nil {
+		t.Fatalf("Mkfifo() error = %v", err)
+	}
+
+	cfg := &config.Config{StableInputs: config.ResolvedStableInputs{
+		SpellCatalogFile: config.ResolvedInputFile{Path: sourcePath, ConfigPath: filepath.Join(root, "campaign.yml")},
+	}}
+	for _, check := range inspectStableInputs(cfg) {
+		if check.Name != "spell_catalog" {
+			continue
+		}
+		if check.Err == nil || !strings.Contains(check.Err.Error(), "not a regular file") {
+			t.Fatalf("spell catalog check = %#v, want regular-file rejection", check)
+		}
+		return
+	}
+	t.Fatal("spell catalog inspection result was not reported")
+}