What causes "size must be greater than 0" in wavetermdev/waveterm?

Set Size to a positive byte count (e.g. 1024 or 4096) before the RPC call

size must be greater than 0

Error message

size must be greater than 0

What it means

Returned when a read request specifies a size that is not greater than zero.

Source

Thrown at pkg/wshrpc/wshserver/wshserver.go:841

	var fileInfoList []*wshrpc.WaveFileInfo
	for _, wf := range fileList {
		fileInfoList = append(fileInfoList, waveFileToWaveFileInfo(wf))
	}
	return &wshrpc.BlockInfoData{
		BlockId:     blockId,
		TabId:       tabId,
		WorkspaceId: workspaceId,
		Block:       blockData,
		Files:       fileInfoList,
	}, nil
}

func (ws *WshServer) DebugTermCommand(ctx context.Context, data wshrpc.CommandDebugTermData) (*wshrpc.CommandDebugTermRtnData, error) {
	if data.BlockId == "" {
		return nil, fmt.Errorf("blockid is required")
	}
	if data.Size <= 0 {
		return nil, fmt.Errorf("size must be greater than 0")
	}
	waveFile, err := filestore.WFS.Stat(ctx, data.BlockId, wavebase.BlockFile_Term)
	if err == fs.ErrNotExist {
		return &wshrpc.CommandDebugTermRtnData{}, nil
	}
	if err != nil {
		return nil, fmt.Errorf("error statting term file: %w", err)
	}
	readSize := data.Size
	dataLength := waveFile.DataLength()
	if readSize > dataLength {
		readSize = dataLength
	}
	readOffset := waveFile.Size - readSize
	readOffset, readData, err := filestore.WFS.ReadAt(ctx, data.BlockId, wavebase.BlockFile_Term, readOffset, readSize)
	if err != nil {
		return nil, fmt.Errorf("error reading term file: %w", err)
	}

View on GitHub (pinned to a4447c1563)

Solutions

Set Size to a positive byte count (e.g. 1024 or 4096) before the RPC call
If you want the whole file, still pass a positive size — the command clamps readSize to the file's actual data length
Check upstream logic that computes Size for accidental zero/negative results

Example fix

// before
data := wshrpc.CommandDebugTermData{BlockId: blockId}
// after
data := wshrpc.CommandDebugTermData{BlockId: blockId, Size: 4096}

Defensive patterns

Strategy: validation

Validate before calling

if data.Size <= 0 {
    return fmt.Errorf("cannot call DebugTermCommand: Size must be > 0")
}

Type guard

func validSize(data wshrpc.CommandDebugTermData) bool {
    return data.Size > 0
}

Try / catch

resp, err := client.DebugTermCommand(ctx, data)
if err != nil {
    if strings.Contains(err.Error(), "size must be greater than 0") {
        // fix payload: set Size > 0
    }
    return err
}

Prevention

Initialize Size explicitly, never rely on zero values
Clamp computed sizes to a minimum of 1
Remember the command clamps oversize reads, so a generous positive size is safe

When it happens

Trigger: Calling DebugTermCommand with CommandDebugTermData.Size left at 0 or set to a negative value.

Common situations: Constructing the data struct without initializing Size (Go zero value); computing a size from an empty variable; typos passing the wrong field.

Understand the failure class

Background: "Must be a positive integer", "Invalid value", "Unsupported": the invalid-argument-value error family, when a library rejects the value you pass — this error's family across 35 libraries.

Related errors

AI-assisted analysis of wavetermdev/waveterm@a4447c1563 (2026-09-01). Data as JSON: /api/errors/fb5b6449b436f5cb. Report an issue: GitHub.