try: pdf = generate_pdf(data) return pdf except Exception as e: logger.error(f"PDF generation failed: str(e)") return jsonify( "success": False, "error": "code": "PDF_RENDER_ERROR", "message": "Report could not be assembled due to invalid data.", "recoverable": False, "userDataPreserved": True ), 200 # still 200 to avoid download interrupt If PDF fails, offer structured data export.
function exportRawData() const formData = collectFormData(); const blob = new Blob([JSON.stringify(formData, null, 2)], type: 'application/json' ); const url = URL.createObjectURL(blob); const a = document.createElement('a'); a.href = url; a.download = 'report-data.json'; a.click(); URL.revokeObjectURL(url); showToast("Raw data saved – you can retry PDF generation later."); gracefully broken pdf download
function logPDFFailure(error, context) navigator.sendBeacon('/api/log-pdf-error', JSON.stringify( errorCode: error.code, userAction: 'download_pdf', timestamp: Date.now(), page: window.location.pathname, dataSize: context.dataSize )); try: pdf = generate_pdf(data) return pdf except Exception
Some browsers treat 4xx/5xx responses as download failures and show generic "Failed – Network error". Step 3: Graceful Failure Response on Frontend When receiving a JSON error instead of a PDF blob, show a user‑friendly overlay. # DON'T DO THIS output = BytesIO() pdf = canvas
# DON'T DO THIS output = BytesIO() pdf = canvas.Canvas(output) pdf.drawString(100, 750, "Report") # crash here – user gets zero-byte or partial PDF