frappe-syntax-serverscripts

name	frappe-syntax-serverscripts
description	Use when writing Python code for ERPNext/Frappe Server Scripts including Document Events, API endpoints, Scheduler Events, and Permission Queries. Prevents the #1 AI mistake: using import statements in Server Scripts (sandbox blocks ALL imports). Covers frappe.* methods, event name mapping, and correct v14/v15/v16 syntax. Keywords: Server Script, frappe, ERPNext, sandbox, import, doc event, validate, on_submit, before_save, server script example, import not allowed, sandbox rules, which script type to use.
license	MIT
compatibility	Claude Code, Claude.ai Projects, Claude API. Frappe v14-v16.
metadata	{"author":"OpenAEC-Foundation","version":"2.0"}

Frappe Server Scripts — Complete Reference

Server Scripts are Python scripts managed via Setup > Server Script in the Frappe/ERPNext UI. They run inside a RestrictedPython sandbox.

CRITICAL: The Sandbox Rule

┌──────────────────────────────────────────────────────────────────┐
│  ALL import STATEMENTS ARE BLOCKED                               │
│                                                                  │
│  import json             → ImportError: __import__ not found     │
│  from datetime import *  → ImportError: __import__ not found     │
│  import frappe           → ImportError (even frappe itself!)     │
│                                                                  │
│  EVERYTHING you need is pre-loaded in the frappe namespace.      │
│  NEVER write an import line. ALWAYS use frappe.utils.*, etc.     │
└──────────────────────────────────────────────────────────────────┘

ALWAYS use the pre-loaded namespace instead of imports:

Blocked import	Use instead
import json	frappe.parse_json() / frappe.as_json()
from datetime import date	frappe.utils.today() / frappe.utils.now_datetime()
from frappe.utils import cint	frappe.utils.cint() (already loaded)
import requests	frappe.make_get_request() / frappe.make_post_request()
import re	Not available — restructure logic without regex
import os / import sys	Not available — use a custom app instead

Enabling Server Scripts

# v14: enabled by default
# v15+: DISABLED by default — you MUST enable explicitly:
bench set-config -g server_script_enabled 1
# Or set server_script_enabled: true in site_config.json

NEVER expect Server Scripts to work on Frappe Cloud shared benches — they require a private bench.

Script Types

Type	Trigger	Key Variable
Document Event	Document lifecycle (save, submit, cancel)	doc
API	HTTP request to /api/method/{name}	frappe.form_dict
Scheduler Event	Cron schedule	(none)
Permission Query	Document list filtering	user, conditions

Event Name Mapping (Document Events)

CRITICAL: The UI names differ from internal hook names:

Server Script UI	Internal Hook	Fires When
Before Insert	before_insert	Before new doc saved to DB
After Insert	after_insert	After first DB insert
Before Validate	before_validate	Before framework validation
Before Save	validate	Before save (new + update)
After Save	on_update	After successful save
Before Submit	before_submit	Before submit (docstatus 0→1)
After Submit	on_submit	After submit completes
Before Cancel	before_cancel	Before cancel (docstatus 1→2)
After Cancel	on_cancel	After cancel completes
Before Delete	on_trash	Before permanent delete
After Delete	after_delete	After permanent delete

NEVER confuse "Before Save" with before_save — the UI label "Before Save" maps to the validate hook. The actual before_save hook runs AFTER validate.

Decision Tree: Server Script vs Document Controller

Need custom Python logic for a DocType?
│
├─► Can you install a custom Frappe app?
│   ├─► YES: Use a Document Controller when you need:
│   │   • import statements (any Python library)
│   │   • File system access
│   │   • Complex class inheritance
│   │   • autoname / before_naming hooks
│   │   • Unit-testable code
│   │
│   └─► NO: Use a Server Script when:
│       • You only have UI access (no bench CLI)
│       • Logic is simple validation / field calculation
│       • You need a quick API endpoint
│       • You need dynamic permission filtering
│
└─► Is logic > 50 lines or needs external libraries?
    ├─► YES → Document Controller in a custom app
    └─► NO  → Server Script is fine

Quick Reference: Available in Sandbox

Pre-loaded Objects

doc                         # Current document (Document Event only)
frappe                      # Core namespace — ALWAYS available
frappe.db                   # Database operations
frappe.utils                # Date, number, string utilities
frappe.session              # Current session (user, csrf_token)
frappe.form_dict            # Request parameters (API scripts)
frappe.response             # Response object (API scripts)
frappe.request              # Werkzeug request object
frappe.qb                   # Query Builder (v14+)
json                        # Python json module (pre-loaded)

Core Methods

# Documents
frappe.get_doc(doctype, name)           # Fetch document
frappe.new_doc(doctype)                 # Create new document
frappe.get_cached_doc(doctype, name)    # Cached fetch (read-only)
frappe.get_last_doc(doctype)            # Most recent document
frappe.get_mapped_doc(...)              # Map fields between DocTypes
frappe.delete_doc(doctype, name)        # Delete document
frappe.rename_doc(doctype, old, new)    # Rename document

# Querying
frappe.get_all(doctype, filters, fields, order_by, limit)   # No permission check
frappe.get_list(doctype, filters, fields, order_by, limit)  # With permission check
frappe.db.get_value(doctype, name, fieldname)
frappe.db.get_single_value(doctype, fieldname)
frappe.db.set_value(doctype, name, fieldname, value)
frappe.db.exists(doctype, name_or_filters)
frappe.db.count(doctype, filters)
frappe.db.sql(query, values, as_dict)   # ALWAYS parameterize!
frappe.db.escape(value)                 # SQL escape
frappe.db.commit()                      # ONLY in Scheduler scripts
frappe.db.rollback()                    # ONLY in Scheduler scripts

# Messaging
frappe.throw(msg, exc, title)           # Stop execution + show error
frappe.msgprint(msg, title, indicator)  # User notification
frappe.log_error(message, title)        # Error Log entry

# HTTP (yes, these work in sandbox!)
frappe.make_get_request(url, params, headers)
frappe.make_post_request(url, data, headers)
frappe.make_put_request(url, data, headers)

# Email
frappe.sendmail(recipients, sender, subject, message)

# Utilities
frappe.utils.today()                    # "2024-01-15"
frappe.utils.now()                      # "2024-01-15 10:30:00"
frappe.utils.now_datetime()             # datetime object
frappe.utils.add_days(date, n)          # Date arithmetic
frappe.utils.add_months(date, n)
frappe.utils.date_diff(d1, d2)          # Days between dates
frappe.utils.flt(val)                   
frappe.utils.cint(val)                  
frappe.utils.cstr(val)                  
frappe.parse_json(string)               
frappe.as_json(obj)                     
frappe.render_template(template, ctx)   
frappe.get_url()                        
frappe.get_hooks(hook)                  
run_script(script_name, **kwargs)       


frappe.session.user                     
frappe.get_roles(user)                  
frappe.has_permission(doctype, ptype, doc)
frappe.get_fullname(user)               
_()               

Python Builtins Available

str, int, float, bool, list, dict, tuple, set  # Types
range, enumerate, zip, map, filter              # Iteration
sum, min, max, len, sorted, reversed            # Aggregation
isinstance, type, hasattr, getattr              # Introspection
all, any, abs, round, divmod                    # Math/logic
print                                           # → server log
True, False, None                               # Constants

Python Builtins BLOCKED

open, file          # No file I/O
eval, exec, compile # No dynamic code execution
__import__          # No imports (this is the root cause)
globals, locals     # No scope introspection

Syntax Per Script Type

Document Event

# Config: Reference DocType = Sales Invoice, Event = Before Save
if doc.grand_total < 0:
    frappe.throw("Total MUST NOT be negative")

doc.requires_approval = 1 if doc.grand_total > 10000 else 0

API

# Config: API Method = get_customer_orders, Allow Guest = No
# Endpoint: /api/method/get_customer_orders
customer = frappe.form_dict.get("customer")
if not customer:
    frappe.throw("Parameter 'customer' is required")

orders = frappe.get_all("Sales Order",
    filters={"customer": customer, "docstatus": 1},
    fields=["name", "grand_total", "status"],
    order_by="creation desc",
    limit=20
)
frappe.response["message"] = {"orders": orders, "count": len(orders)}

Scheduler Event

# Config: Event Frequency = Cron, Cron Format = 0 9 * * *
overdue = frappe.get_all("Sales Invoice",
    filters={"status": "Unpaid", "due_date": ["<", frappe.utils.today()], "docstatus": 1},
    fields=["name", "customer", "grand_total"]
)
for inv in overdue:
    frappe.log_error(f"Overdue: {inv.name} ({inv.customer})", "Invoice Reminder")

frappe.db.commit()  # ALWAYS commit in Scheduler scripts

Permission Query

# Config: Reference DocType = Sales Invoice
# Variables available: user, conditions
roles = frappe.get_roles(user)
if "System Manager" in roles:
    conditions = ""
elif "Sales User" in roles:
    conditions = f"`tabSales Invoice`.owner = {frappe.db.escape(user)}"
else:
    conditions = "1=0"

Version Differences

Feature	v14	v15	v16
Server Scripts enabled	By default	Disabled by default	Disabled by default
Enable command	Not needed	bench set-config -g server_script_enabled 1	Same as v15
frappe.qb (Query Builder)	Available	Available	Available
run_script() for libraries	v13+	Available	Available
frappe.make_get_request()	Available	Available	Available
Frappe Cloud shared bench	Supported	NOT supported	NOT supported

Top 5 Rules

1. NEVER write import — everything is in the frappe namespace
2. NEVER call doc.save() inside a Before Save script — causes infinite loop
3. NEVER call frappe.db.commit() in Document Event scripts — framework handles it
4. ALWAYS call frappe.db.commit() at the end of Scheduler scripts
5. ALWAYS use parameterized queries: %(var)s with dict, NEVER f-strings in SQL

References

• references/methods.md — Complete sandbox API reference
• references/events.md — Document lifecycle and execution order
• references/examples.md — Working examples per script type
• references/anti-patterns.md — Sandbox violations and common mistakes
• references/syntax.md — Quick syntax cheat sheet
• references/patterns.md — Common patterns (validation, auto-fill, API)
• references/hooks.md — Server Scripts vs hooks.py interaction

Cross-References

• frappe-syntax-api — Frappe REST API and whitelisted methods
• frappe-syntax-doctype — DocType field types and schema
• frappe-core-database — frappe.db deep dive
• frappe-core-permissions — Permission system architecture
• frappe-errors-common — Error handling patterns