OpenAEC-Foundation/frappe-errors-serverscripts

Server Script Errors — Diagnosis and Resolution

Cross-refs: frappe-syntax-serverscripts (syntax), frappe-impl-serverscripts (workflows), frappe-errors-clientscripts (client-side).

---

CRITICAL: Server Scripts Disabled by Default [v15+]

Starting from Frappe v15, Server Scripts are disabled by default. You MUST enable them:

# In site_config.json
{ "server_script_enabled": 1 }

On Frappe Cloud: Server Scripts are ONLY available on private benches, NOT on shared benches.

---

Error Diagnosis Flowchart

ERROR IN SERVER SCRIPT
│
├─► ImportError / NameError
│   ├─► "import json" → BLOCKED. Use frappe.parse_json()
│   ├─► "import datetime" → BLOCKED. Use frappe.utils
│   ├─► "import os/sys/subprocess" → BLOCKED. Security restriction
│   └─► "NameError: name 'dict' is not defined" → Some builtins restricted
│
├─► SyntaxError: not allowed
│   ├─► "try/except" → BLOCKED by RestrictedPython [v14-v15]
│   ├─► "raise ValueError" → BLOCKED. Use frappe.throw()
│   └─► "exec/eval" → BLOCKED. Security restriction
│
├─► Script runs but nothing happens
│   ├─► Wrong Script Type selected → Check Document Event vs API vs Scheduler
│   ├─► Wrong DocType selected → Verify exact DocType name
│   ├─► Wrong Event selected → Before Save ≠ After Save
│   └─► Script disabled → Check "Enabled" checkbox
│
├─► 403 Permission Denied
│   ├─► Scheduler script → Runs as Administrator, check role permissions
│   ├─► API script → Check Allow Guest setting
│   └─► doc_event → User lacks DocType permission
│
├─► Data not saved in Scheduler
│   └─► Missing frappe.db.commit() → REQUIRED in scheduler scripts
│
└─► API script returns empty/wrong response
    └─► Not setting frappe.response["message"] → ALWAYS set response

---

Error Message → Cause → Fix Table

| Error Message | Cause | Fix | |---------------|-------|-----| | ImportError: import not allowed | Any import statement in sandbox | Use frappe.utils, frappe.parse_json(), etc. | | NameError: name 'dict' is not defined | Some Python builtins blocked by RestrictedPython | Use frappe._dict() or literal {} | | SyntaxError: try/except not allowed | RestrictedPython blocks exception handling [v14-v15] | Use conditional checks (if/else) instead | | SyntaxError: raise not allowed | RestrictedPython blocks raise | Use frappe.throw() | | Script not executing | Wrong Script Type or Event selected | Verify type matches: Document Event, API, or Scheduler | | doc is not defined | Using doc in API or Scheduler script (no document context) | doc is only available in Document Event scripts | | PermissionError in Scheduler | Scheduler runs as Administrator but script accesses restricted resource | Use ignore_permissions=True where appropriate | | Changes not saved in Scheduler | Missing frappe.db.commit() | ALWAYS call frappe.db.commit() in Scheduler scripts | | API returns empty response | Forgot to set frappe.response["message"] | ALWAYS set frappe.response["message"] = result | | Timeout / killed | Infinite loop or processing too many records | ALWAYS add limit to queries, ALWAYS use batch processing | | ValidationError: qty is required | doc.save() called in Before Save (recursion) | NEVER call doc.save() in Before Save; just set values | | SQL injection via string format | User input in SQL without escaping | ALWAYS use frappe.db.escape() or parameterized queries |

---

The #1 Error: ImportError

Every beginner hits this. The Server Script sandbox blocks ALL imports except json.

# ❌ BLOCKED — These ALL fail with ImportError
import json                    # Use frappe.parse_json() / frappe.as_json()
from datetime import datetime  # Use frappe.utils.now(), frappe.utils.today()
import re                      # Not available in sandbox
import os                      # Security: blocked
import requests                # Use frappe.make_get_request(), frappe.make_post_request()

# ✅ CORRECT — Sandbox equivalents
data = frappe.parse_json(doc.json_field)         # Instead of json.loads()
today = frappe.utils.today()                      # Instead of datetime.date.today()
now = frappe.utils.now()                          # Instead of datetime.now()
diff = frappe.utils.date_diff(date1, date2)       # Instead of timedelta
resp = frappe.make_get_request("https://api.com") # Instead of requests.get()
resp = frappe.make_post_request("https://api.com", data=payload)

Available Sandbox API (Complete Reference)

| Category | Available Methods | |----------|-------------------| | Document | frappe.get_doc(), frappe.new_doc(), frappe.get_last_doc(), frappe.get_cached_doc(), frappe.get_mapped_doc(), frappe.rename_doc(), frappe.delete_doc() | | Database | frappe.db.get_list(), frappe.db.get_all(), frappe.db.get_value(), frappe.db.get_single_value(), frappe.db.set_value(), frappe.db.exists(), frappe.db.sql(), frappe.db.commit(), frappe.db.rollback(), frappe.db.escape() | | Query Builder | frappe.qb (full query builder) | | HTTP | frappe.make_get_request(), frappe.make_post_request(), frappe.make_put_request() | | Utility | frappe.utils.* (all utility functions), frappe.parse_json(), frappe.as_json() | | User/Session | frappe.session.user, frappe.get_roles(), frappe.has_permission() | | Messages | frappe.throw(), frappe.msgprint(), frappe.log_error(), frappe.sendmail() | | Module | json (the ONLY importable module) |

---

Script Type Selection Errors

ALWAYS verify you selected the correct Script Type:

| Script Type | Trigger | Has doc? | Has frappe.form_dict? | Auto-commit? | |-------------|---------|:----------:|:-----------------------:|:------------:| | Document Event | DocType lifecycle (Before Save, After Save, etc.) | YES | NO | YES | | API | HTTP request to /api/method/{method_name} | NO | YES | YES | | Scheduler Event | Cron schedule | NO | NO | NO — MUST call frappe.db.commit() | | Permission Query | Every list query on the DocType | NO | NO (has user) | N/A |

Common Mistake: Wrong Event

# ❌ WRONG — "After Save" cannot prevent save
# Script Type: Document Event, Event: After Save
if not doc.customer:
    frappe.throw("Customer is required")  # Document already saved!

# ✅ CORRECT — Use "Before Save" or "Before Validate"
# Script Type: Document Event, Event: Before Save
if not doc.customer:
    frappe.throw("Customer is required")  # Prevents save

---

Sandbox Workarounds

try/except Is Blocked: Use Conditional Checks

# ❌ BLOCKED in sandbox
try:
    customer = frappe.get_doc("Customer", doc.customer)
except Exception:
    frappe.throw("Customer not found")

# ✅ CORRECT — Check first, then access
if not frappe.db.exists("Customer", doc.customer):
    frappe.throw(f"Customer '{doc.customer}' not found")
customer = frappe.get_doc("Customer", doc.customer)

raise Is Blocked: Use frappe.throw()

# ❌ BLOCKED
if amount < 0:
    raise ValueError("Amount cannot be negative")

# ✅ CORRECT
if amount < 0:
    frappe.throw("Amount cannot be negative")

frappe.throw() Exception Types for API Scripts

| Exception | HTTP Code | Use When | |-----------|:---------:|----------| | frappe.ValidationError | 417 | Input validation failure | | frappe.PermissionError | 403 | Access denied | | frappe.DoesNotExistError | 404 | Record not found | | frappe.AuthenticationError | 401 | Not logged in | | (default, no exc) | 417 | General validation error |

# API Script — Correct exception types
if not customer:
    frappe.throw("Customer param required", exc=frappe.ValidationError)  # 417
if not frappe.db.exists("Customer", customer):
    frappe.throw("Customer not found", exc=frappe.DoesNotExistError)    # 404
if not frappe.has_permission("Customer", "read", customer):
    frappe.throw("Access denied", exc=frappe.PermissionError)           # 403

---

Scheduler Script: Critical Mistakes

# ❌ WRONG — No limit, no commit, no error logging
invoices = frappe.get_all("Sales Invoice", filters={"status": "Unpaid"})
for inv in invoices:
    frappe.db.set_value("Sales Invoice", inv.name, "reminder_sent", 1)

# ✅ CORRECT — Limit, batch commit, error logging
BATCH_SIZE = 50
invoices = frappe.get_all(
    "Sales Invoice",
    filters={"status": "Unpaid", "docstatus": 1},
    fields=["name", "customer"],
    limit=500  # ALWAYS limit
)

errors = []
for i in range(0, len(invoices), BATCH_SIZE):
    batch = invoices[i:i + BATCH_SIZE]
    for inv in batch:
        if not frappe.db.exists("Customer", inv.customer):
            errors.append(f"{inv.name}: Customer not found")
            continue
        frappe.db.set_value("Sales Invoice", inv.name, "reminder_sent", 1)
    frappe.db.commit()  # REQUIRED

if errors:
    frappe.log_error("\n".join(errors), "Reminder Errors")
frappe.db.commit()

---

SQL Injection Prevention

# ❌ VULNERABLE — String interpolation with user input
territory = frappe.form_dict.get("territory")
conditions = f"`tabCustomer`.territory = '{territory}'"  # SQL INJECTION!

# ✅ SAFE — Use frappe.db.escape()
territory = frappe.form_dict.get("territory")
conditions = f"`tabCustomer`.territory = {frappe.db.escape(territory)}"

# ✅ SAFEST — Use parameterized query or Query Builder
results = frappe.db.get_all("Customer", filters={"territory": territory})

---

ALWAYS / NEVER Rules

ALWAYS

1. Use frappe.utils.* instead of Python imports — Only json module is importable
2. Use frappe.throw() instead of raise — raise is blocked by sandbox
3. Use conditional checks instead of try/except — Exception handling is blocked [v14-v15]
4. Call frappe.db.commit() in Scheduler scripts — Changes are NOT auto-committed
5. Add limit to ALL queries in Scheduler scripts — Prevent memory exhaustion
6. Set frappe.response["message"] in API scripts — Otherwise response is empty
7. Use frappe.db.escape() for user input in SQL — Prevent SQL injection
8. Log errors in Scheduler scripts with frappe.log_error() — No user to see errors
9. Verify Script Type matches your intent — Document Event vs API vs Scheduler

NEVER

1. NEVER use import statements (except json) — Blocked by RestrictedPython
2. NEVER use try/except or raise — Blocked by sandbox [v14-v15]
3. NEVER call doc.save() in Before Save — Causes infinite recursion
4. NEVER use string formatting for SQL with user input — SQL injection risk
5. NEVER process unlimited records in Scheduler — Always use limit
6. NEVER assume doc exists in API/Scheduler scripts — Only available in Document Events
7. NEVER forget frappe.db.commit() in Scheduler — All changes will be lost

---

Reference Files

| File | Contents | |------|----------| | references/examples.md | Real error scenarios with diagnosis | | references/anti-patterns.md | Common sandbox mistakes with fixes | | references/patterns.md | Defensive error handling patterns by script type |