github/github-mcp-server · info

failed to flush CSV: %w

Error message

failed to flush CSV: %w

What it means

writer.Error() reported a failure after Flush while finishing the CSV document in jsonTextToCSV. encoding/csv defers underlying-writer errors to this call, but the destination is a bytes.Buffer whose writes never fail, so this branch guards against conditions that cannot occur in the stock implementation (e.g., a fork writing to a network stream). It fires only after all rows were already buffered.

Source

Thrown at pkg/github/csv_output.go:150

	writer := csv.NewWriter(&buf)
	if err := writer.Write(headers); err != nil {
		return "", fmt.Errorf("failed to write CSV header: %w", err)
	}

	for _, row := range doc.rows {
		record := make([]string, len(headers))
		for i, header := range headers {
			record[i] = row[header]
		}
		if err := writer.Write(record); err != nil {
			return "", fmt.Errorf("failed to write CSV row: %w", err)
		}
	}

	writer.Flush()
	if err := writer.Error(); err != nil {
		return "", fmt.Errorf("failed to flush CSV: %w", err)
	}
	return buf.String(), nil
}

func csvDocument(value any) csvOutputDocument {
	switch v := value.(type) {
	case []any:
		return csvOutputDocument{rows: csvRowsFromArray(v)}
	case map[string]any:
		if rows, metadata, ok := primaryRowsFromMap(v); ok {
			return csvOutputDocument{
				metadata: newFlattenedCSVRow(metadata),
				rows:     csvRowsFromArray(rows),
			}
		}
		return csvOutputDocument{rows: []map[string]string{newFlattenedCSVRow(v)}}
	default:
		return csvOutputDocument{rows: []map[string]string{scalarCSVRow(v)}}

View on GitHub (pinned to 0ea1f775a7)

Solutions

1. Treat as an invariant violation in stock builds and report upstream with logs
2. In forks writing to fallible destinations, handle the error at the writer level and surface it to the caller
3. Keep conversions bounded (pagination) to avoid extreme buffer growth

writer.Flush()
if err := writer.Error(); err != nil {
	// buffered content is complete in memory: log, and if the destination is fallible, return partial output with a truncation flag
	return "", fmt.Errorf("failed to flush CSV: %w", err)
}

When it happens

Trigger: Completing a CSV conversion where the deferred writer error is non-nil — only possible in modified builds using a fallible destination or under memory corruption.

Common situations: Forks streaming CSV to sockets/files; official in-memory conversion cannot produce this error.

Related errors

• failed to write CSV header: %w
• failed to write CSV row: %w
• failed to unmarshal JSON text: %w
• failed to marshal discussions: %w
• failed to marshal discussion: %w

AI-assisted analysis of github/github-mcp-server@0ea1f775a7 (2026-08-15). Data as JSON: /api/errors/3a94382108443591. Report an issue: GitHub.