msg       string // description of error
	context   string // additional error context
	pos       errPos
	atChar    byte
	readerErr error // underlying reader error, if any
}

// ReaderErr returns the underlying error.
func (e DecoderError) ReaderErr() error { return e.readerErr }

// Error returns a string representation of the error.
func (e DecoderError) Error() string {

	// Reader
	var readErr error
	var wg sync.WaitGroup
	wg.Add(1)
	go func() {
		defer wg.Done()
		defer rb.CloseWithError(readErr)
		readRng := rand.New(rand.NewSource(1))
		buf := make([]byte, 64<<10)
		for {
			// Read
			n, err := rb.Read(buf[:readRng.Intn(len(buf))])
			readBytes += n
			read.Write(buf[:n])
			if err != nil {
				readErr = err
				break
			}

	var i int
	r := bytes.NewReader(data)
	scanner := newScanner(r)
	for scanner.pos < atomic.LoadInt64(&scanner.end) {
		c := scanner.next()
		if scanner.readerErr != nil {
			t.Fatal(scanner.readerErr)
		}
		if c != data[i] {
			t.Fatalf("expected %s, got %s", string(data[i]), string(c))
		}
		t.Logf("pos=%d remaining=%d (%s)", i, r.Len(), string(c))
		i++
	}
}

	end       int64
	buf       [chunk + 1]byte // internal buffer (with a lookback size of 1)
	nbuf      [chunk]byte     // next internal buffer
	fillReq   chan struct{}
	fillReady chan int64
	readerErr error // underlying reader error, if any
}

func newScanner(r io.Reader) *scanner {
	sr := &scanner{
		end:       maxInt,
		fillReq:   make(chan struct{}),
		fillReady: make(chan int64),
	}

	go func() {

	if len(p) == 0 {
		return 0, r.readErr(false)
	}

	r.mu.Lock()
	defer r.mu.Unlock()
	if err := r.readErr(true); err != nil {
		return 0, err
	}

	r.wg.Add(1)
	defer r.wg.Done()
	n, err = r.read(p)
	for err == ErrIsEmpty && r.block {
		r.writeCond.Wait()
		if err = r.readErr(true); err != nil {
			break
		}
		n, err = r.read(p)
	}

func (b *Reader) Read(p []byte) (n int, err error) {
	n = len(p)
	if n == 0 {
		if b.Buffered() > 0 {
			return 0, nil
		}
		return 0, b.readErr()
	}
	if b.r == b.w {
		if b.err != nil {
			return 0, b.readErr()
		}
		if len(p) >= len(b.buf) {
			// Large read, empty buffer.
			// Read directly into p to avoid copy.
			n, b.err = b.rd.Read(p)
			if n < 0 {

	if err != io.EOF {
		t.Fatal(err)
	}
}

func Test_metacacheReader_readAll(t *testing.T) {
	r := loadMetacacheSample(t)
	defer r.Close()
	var readErr error
	objs := make(chan metaCacheEntry, 1)
	var wg sync.WaitGroup
	wg.Add(1)
	go func() {
		readErr = r.readAll(t.Context(), objs)
		wg.Done()
	}()
	want := loadMetacacheSampleNames
	i := 0
	for entry := range objs {
		if entry.name != want[i] {

	return found < notFound && found > 0
}

func danglingMetaErrsCount(cerrs []error) (notFoundCount int, nonActionableCount int) {
	for _, readErr := range cerrs {
		if readErr == nil {
			continue
		}
		switch {
		case errors.Is(readErr, errFileNotFound) || errors.Is(readErr, errFileVersionNotFound):
			notFoundCount++
		default:
			// All other errors are non-actionable
			nonActionableCount++
		}
	}

	if len(context) > 0 {
		err.context = context[0]
	}
	err.atChar = d.cur()
	err.pos[0] = d.lineNo + 1
	err.pos[1] = int(d.pos - d.lineStart)
	err.readerErr = d.readerErr
	return err

	if err == nil {
		t.Fatalf("missing expected decoder error")
	}

	derr, ok := err.(DecoderError)
	if !ok {
		t.Fatalf("expected error of type DecoderError, got %T", err)
	}

	if derr.ReaderErr() == nil {
		t.Fatalf("missing expected underlying reader error")
	}
}

func TestDecoderMaxDepth(t *testing.T) {
	tests := []struct {
		input    string
		maxDepth int
		mustFail bool
	}{