Server Scripts — Implementation Workflows

Step-by-step workflows for building server-side features without a custom app. For exact syntax, see frappe-syntax-serverscripts.

Version: v14/v15/v16 | v15+ Note: Server Scripts disabled by default — enable with bench set-config server_script_enabled true

CRITICAL: Sandbox Limitations

ALL IMPORTS BLOCKED — RestrictedPython sandbox
  import json          → ImportError: __import__ not found
  from frappe.utils    → ImportError
  import requests      → ImportError

SOLUTION: Use pre-loaded namespace:
  frappe.utils.nowdate()        frappe.utils.flt()
  frappe.parse_json(data)       json.loads() (json IS available)
  frappe.as_json(obj)           json.dumps()
  frappe.make_get_request(url)  (replaces requests.get)

Rule: If you need import statements beyond json, ALWAYS use a Controller instead.

Workflow 1: Create a Server Script

1. Enable server scripts: bench set-config server_script_enabled true
2. Navigate to Setup > Server Script (or awesomebar: "New Server Script")
3. Select Script Type (see decision tree below)
4. Configure type-specific settings (DocType, event, API method, cron)
5. Write script in the editor
6. Save — script is active immediately
7. Test by triggering the configured event
8. Use "Compare Versions" button to diff changes

Workflow 2: Choose the Script Type

WHAT DO YOU NEED?
│
├── React to document save/submit/cancel?
│   └── Document Event
│       └── Select DocType + Event (Before Save, After Save, etc.)
│
├── Create a REST API endpoint?
│   └── API
│       └── Set method name + guest access setting
│       └── Endpoint: /api/method/{method_name}
│
├── Run task on schedule (daily/hourly/cron)?
│   └── Scheduler Event
│       └── Set cron pattern or frequency
│
└── Filter list views per user/role?
    └── Permission Query
        └── Select DocType — set `conditions` variable

See references/decision-tree.md for complete decision tree.

Workflow 3: Document Event: Validation

Goal: Validate Sales Order before save.

Step 1: Choose event — "Before Save" maps to validate hook.

Step 2: Write sandbox-safe script:

# Type: Document Event | Event: Before Save | DocType: Sales Order

errors = []

if not doc.customer:
    errors.append("Customer is required")

if doc.delivery_date and doc.delivery_date < frappe.utils.today():
    errors.append("Delivery date cannot be in the past")

for item in doc.items:
    if item.qty <= 0:
        errors.append(f"Row {item.idx}: Quantity must be positive")

if errors:
    frappe.throw("<br>".join(errors), title="Validation Error")

Rules:

• ALWAYS collect errors and throw once (better UX than multiple throws)
• NEVER call doc.save() in Before Save — framework handles it
• ALWAYS use frappe.throw() — msgprint does NOT stop save

Workflow 4: Document Event: Auto-Calculate

Goal: Auto-calculate totals and set derived fields.

# Type: Document Event | Event: Before Save | DocType: Purchase Order

doc.total_qty = sum(item.qty or 0 for item in doc.items)
doc.total_amount = sum((item.qty or 0) * (item.rate or 0) for item in doc.items)

if doc.total_amount > 50000:
    doc.requires_approval = 1
    doc.approval_status = "Pending"

if doc.supplier and not doc.supplier_name:
    doc.supplier_name = frappe.db.get_value("Supplier", doc.supplier, "supplier_name")

Rule: ALWAYS modify doc fields directly in Before Save — they are automatically persisted.

Workflow 5: Document Event: Create Related Document

Goal: Create a ToDo when a new Lead is inserted.

# Type: Document Event | Event: After Insert | DocType: Lead

frappe.get_doc({
    "doctype": "ToDo",
    "allocated_to": doc.lead_owner or doc.owner,
    "reference_type": "Lead",
    "reference_name": doc.name,
    "description": f"Follow up with new lead: {doc.lead_name}",
    "date": frappe.utils.add_days(frappe.utils.today(), 1),
    "priority": "High" if doc.status == "Hot" else "Medium"
}).insert(ignore_permissions=True)

Rules:

• ALWAYS use After Insert or After Save for creating related docs
• NEVER create documents in Before Save — doc.name may not exist yet
• ALWAYS use ignore_permissions=True for system-generated documents

Workflow 6: API Endpoint

Goal: Create authenticated REST API returning customer data.

# Type: API | Method: get_customer_dashboard | Allow Guest: No
# Endpoint: /api/method/get_customer_dashboard

customer = frappe.form_dict.get("customer")
if not customer:
    frappe.throw("Parameter 'customer' is required")

# ALWAYS check permissions
if not frappe.has_permission("Customer", "read", customer):
    frappe.throw("Access denied", frappe.PermissionError)

orders = frappe.db.count("Sales Order", {"customer": customer, "docstatus": 1})
revenue = frappe.db.get_value("Sales Invoice",
    filters={"customer": customer, "docstatus": 1},
    fieldname="sum(grand_total)") or 0

frappe.response["message"] = {
    "customer": customer,
    "total_orders": orders,
    "total_revenue": revenue
}

Rules:

• ALWAYS validate input parameters
• ALWAYS check permissions (even with Allow Guest: No)
• ALWAYS cap query limits: min(frappe.utils.cint(limit), 100)
• NEVER expose full documents — return only needed fields

Workflow 7: Scheduler Event

Goal: Daily reminder for overdue invoices.

# Type: Scheduler Event | Cron: 0 9 * * * (daily at 9:00)

BATCH_SIZE = 50
today = frappe.utils.today()

overdue = frappe.get_all("Sales Invoice",
    filters={
        "status": "Unpaid",
        "due_date": ["<", today],
        "docstatus": 1
    },
    fields=["name", "customer", "owner", "due_date", "grand_total"],
    limit=BATCH_SIZE
)

for inv in overdue:
    days = frappe.utils.date_diff(today, inv.due_date)
    if not frappe.db.exists("ToDo", {
        "reference_type": "Sales Invoice",
        "reference_name": inv.name,
        "status": "Open"
    }):
        frappe.get_doc({
            "doctype": "ToDo",
            "allocated_to": inv.owner,
            "reference_type": "Sales Invoice",
            "reference_name": inv.name,
            "description": f"Invoice {inv.name} is {days} days overdue"
        }).insert(ignore_permissions=True)

frappe.db.commit()  # REQUIRED in scheduler scripts

Rules:

• ALWAYS add frappe.db.commit() at end of scheduler scripts
• ALWAYS add limit to queries — prevent memory exhaustion
• ALWAYS use try/except + frappe.log_error() in loops
• NEVER run scheduler scripts that process unlimited records

Workflow 8: Permission Query

Goal: Users see only their territory's customers.

# Type: Permission Query | DocType: Customer

user_territory = frappe.db.get_value("User", user, "territory")
user_roles = frappe.get_roles(user)

if "System Manager" in user_roles:
    conditions = ""  # Full access
elif user_territory:
    conditions = f"`tabCustomer`.territory = {frappe.db.escape(user_territory)}"
else:
    conditions = f"`tabCustomer`.owner = {frappe.db.escape(user)}"

Rules:

• ALWAYS give System Manager full access (conditions = "")
• ALWAYS use frappe.db.escape() for user input in SQL
• ALWAYS set conditions variable — it is the output
• Permission Query only affects frappe.db.get_list, NOT frappe.db.get_all

Event Name Mapping

Sandbox-Safe API Quick Reference

When to Migrate to Controller

ALWAYS migrate to a Document Controller when:

• You need import statements (beyond json)
• Script exceeds 100 lines
• You need try/except with rollback
• You need frappe.enqueue() for background jobs
• You need to extend an existing ERPNext DocType
• Multiple scripts on same DocType become hard to manage

Migration path: See frappe-impl-controllers for controller implementation.

Related Skills

• frappe-syntax-serverscripts — Exact sandbox API reference
• frappe-errors-serverscripts — Error handling and anti-patterns
• frappe-core-database — frappe.db.* operations
• frappe-core-permissions — Permission system details
• frappe-impl-controllers — When to migrate from Server Script

See references/decision-tree.md for complete decision trees. See references/workflows.md for extended patterns. See references/examples.md for 10+ complete examples.