Release reporter destination references after finalization

reporter_test.go

@@ -2,6 +2,7 @@ package commandkit
 
 import (
 	"bytes"
+	"context"
 	"errors"
 	"io"
 	"strings"
@@ -710,3 +711,39 @@ func setReporterVisibility(reporter *Reporter, mode reportingMode, progress, pro
 	}
 	reporter.applySelection(selection)
 }
+
+func TestReporterFinalizationReleasesBorrowedDestinations(t *testing.T) {
+	cause := errors.New("operation failed")
+	for _, tc := range []struct {
+		name    string
+		outcome Outcome
+		cause   error
+	}{
+		{name: "success", outcome: Success()},
+		{name: "failure", outcome: Failure("failed").WithCause(cause), cause: cause},
+		{name: "cancellation", outcome: Failure("canceled").WithCause(context.Canceled), cause: context.Canceled},
+	} {
+		t.Run(tc.name, func(t *testing.T) {
+			out, diagnostics := &callerOwnedWriter{}, &callerOwnedWriter{}
+			reporter := newReporter(Streams{Out: out, Err: diagnostics})
+			output, deferred := reporter.Output(), reporter.AtEnd()
+			result := reporter.finalize(tc.outcome, nil)
+			if reporter.state.output.writer != nil || reporter.state.diagnostics.writer != nil || out.closeCalls != 0 || diagnostics.closeCalls != 0 || tc.cause != nil && !errors.Is(result.Cause, tc.cause) {
+				t.Fatalf("outcome=%#v state=%#v", result, reporter.state)
+			}
+			outLen, diagnosticLen := out.Len(), diagnostics.Len()
+			if _, err := output.Write([]byte("late")); !errors.Is(err, ErrReporterClosed) {
+				t.Errorf("output error=%v", err)
+			}
+			if err := reporter.Warn("late"); !errors.Is(err, ErrReporterClosed) {
+				t.Errorf("reporter error=%v", err)
+			}
+			if err := deferred.Warn("late"); !errors.Is(err, ErrReporterClosed) {
+				t.Errorf("deferred error=%v", err)
+			}
+			if out.Len() != outLen || diagnostics.Len() != diagnosticLen {
+				t.Fatal("late operation touched destinations")
+			}
+		})
+	}
+}