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Frappe Syntax Serverscripts

impertio-studio/frappe-syntax-serverscripts

> Use when writing Python code for ERPNext/Frappe Server Scripts including Document Events, API endpoints, Scheduler Events, and Permission Queries. (sandbox blocks ALL imports). Covers frappe.* methods, event name mapping, sandbox, import, doc event, validate, on_submit, before_save, server script example, import not allowed, sandbox rules, which script type to use.

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Install

one command, takes just this skill from the repository
npx skills add https://github.com/Impertio-Studio/Frappe_Claude_Skill_Package --skill frappe-syntax-serverscripts

The instruction itself

20 sections, as written by the author

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)                   # Safe float (None → 0.0)
frappe.utils.cint(val)                  # Safe int (None → 0)
frappe.utils.cstr(val)                  # Safe string (None → "")
frappe.parse_json(string)               # JSON string → dict/list
frappe.as_json(obj)                     # dict/list → JSON string
frappe.render_template(template, ctx)   # Jinja rendering
frappe.get_url()                        # Site URL
frappe.get_hooks(hook)                  # Read app hooks
run_script(script_name, **kwargs)       # Call another Server Script

# Session / Permissions
frappe.session.user                     # Current user email
frappe.get_roles(user)                  # User's roles list
frappe.has_permission(doctype, ptype, doc)
frappe.get_fullname(user)               # User's display name
_("translatable string")               # Translation function

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

  • NEVER write import — everything is in the frappe namespace
  • NEVER call doc.save() inside a Before Save script — causes infinite loop
  • NEVER call frappe.db.commit() in Document Event scripts — framework handles it
  • ALWAYS call frappe.db.commit() at the end of Scheduler scripts
  • 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

How to use it

Copy the folder

Take impertio-studio/frappe-syntax-serverscripts from the repository into ~/.claude/skills for personal use, or into .claude/skills inside a project.

Check the name does not clash

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