Frappe Hooks Error Diagnosis & Resolution

Cross-ref: frappe-syntax-hooks (syntax), frappe-impl-hooks (workflows), frappe-errors-controllers (controller errors).

Error-to-Fix Mapping Table

Error / Symptom	Cause	Fix
Hook not firing at all	Typo in dotted path	Verify module path matches actual file location
`ImportError` on bench start	Wrong module path or circular import	Fix import path; break circular dependency
`AttributeError: module has no attribute`	Function name typo in hooks.py	Match function name exactly to Python definition
`app_include_js` not loading	Path missing `assets/` prefix or wrong extension	Use `"assets/myapp/js/file.js"` format
scheduler_events not running	Scheduler disabled or workers down	`bench scheduler enable`, check `bench doctor`
doc_events handler never called	DocType name misspelled in dict key	Use exact DocType name with spaces: `"Sales Invoice"`
`permission_query_conditions` breaks list view	SQL syntax error or frappe.throw() in handler	Return valid SQL string; NEVER throw
`override_doctype_class` import failure	Parent class import path changed between versions	Pin import to correct module path for target version
`extend_doctype_class` [v16+] method conflict	Two extensions define same method name	Rename conflicting methods; check hook resolution order
Fixtures not loading on install	Wrong `dt` key or DocType doesn't exist on target	Verify DocType exists before export; check filter syntax
`extend_bootinfo` breaks login	Unhandled exception in boot handler	Wrap ALL bootinfo code in try/except
Wildcard `"*"` handler breaks all saves	Unhandled exception in wildcard doc_events	ALWAYS wrap wildcard handlers in try/except
Hook fires but changes lost	Missing `frappe.db.commit()` in scheduler	Add explicit commit in scheduler/background tasks
Multiple handler chain broken	First handler throws, others never run	Isolate non-critical ops in try/except

Hook Registration Errors

Hook Not Firing: Diagnosis Checklist

IS YOUR HOOK NOT FIRING?
│
├─► Check 1: Is the dotted path correct?
│   hooks.py: "myapp.events.sales.validate"
│   File:     myapp/events/sales.py → def validate(doc, method=None):
│   COMMON MISTAKE: "myapp.events.sales_invoice.validate" when file is sales.py
│
├─► Check 2: Is the dict structure correct?
│   doc_events uses NESTED dict: {"Sales Invoice": {"validate": "path"}}
│   scheduler_events uses LIST: {"daily": ["path1", "path2"]}
│   permission_query uses FLAT dict: {"Sales Invoice": "path"}
│
├─► Check 3: Is bench restarted after hooks.py change?
│   ALWAYS run: bench restart (or bench clear-cache for dev)
│
├─► Check 4: Is the DocType name exact?
│   "Sales Invoice" NOT "SalesInvoice" NOT "sales_invoice"
│   Use exact DocType name as shown in Frappe UI
│
└─► Check 5: Is the app installed on the site?
    bench --site mysite list-apps

Circular Import Errors

# ❌ CAUSES ImportError — circular dependency
# myapp/hooks.py imports from myapp.events
# myapp/events/sales.py imports from myapp.hooks

# ✅ CORRECT — break the cycle
# Move shared constants to myapp/constants.py
# Import from constants in both hooks.py and events/

Rule: NEVER import from hooks.py in your event handlers. hooks.py is read by the framework, not imported by your code.

Wrong Dict Structure by Hook Type

# ❌ WRONG — doc_events needs nested dict, not flat
doc_events = {
    "Sales Invoice": "myapp.events.validate"  # WRONG: string, not dict
}

# ✅ CORRECT
doc_events = {
    "Sales Invoice": {
        "validate": "myapp.events.sales.validate"
    }
}

# ❌ WRONG — scheduler_events daily needs list
scheduler_events = {
    "daily": "myapp.tasks.daily_sync"  # WRONG: string, not list
}

# ✅ CORRECT
scheduler_events = {
    "daily": ["myapp.tasks.daily_sync"]
}

# ❌ WRONG — cron needs nested dict with list values
scheduler_events = {
    "cron": ["0 9 * * *", "myapp.tasks.morning"]  # WRONG structure
}

# ✅ CORRECT
scheduler_events = {
    "cron": {
        "0 9 * * 1-5": ["myapp.tasks.morning_report"]
    }
}

app_include_js / app_include_css Errors

# ❌ WRONG — missing assets/ prefix
app_include_js = "js/myapp.js"

# ❌ WRONG — using Python module path instead of file path
app_include_js = "myapp.public.js.myapp"

# ✅ CORRECT — full asset path
app_include_js = "assets/myapp/js/myapp.js"

# ✅ CORRECT — multiple files as list
app_include_js = ["assets/myapp/js/app.js", "assets/myapp/js/utils.js"]
app_include_css = "assets/myapp/css/myapp.css"

Diagnosis: If JS/CSS not loading, check browser DevTools Network tab for 404. Run bench build after adding new files. ALWAYS verify the file exists at myapp/public/js/myapp.js.

scheduler_events Not Running

Diagnosis Steps

# Step 1: Is scheduler enabled?
bench scheduler status
# If disabled: bench scheduler enable

# Step 2: Are workers running?
bench doctor
# Look for: "Workers online: X"
# If 0: bench start (dev) or supervisorctl restart all (prod)

# Step 3: Check Scheduled Job Log
# In Frappe UI: /api/method/frappe.client.get_list?doctype=Scheduled Job Log&limit=5

# Step 4: Check Error Log for task failures
# In Frappe UI: /app/error-log

# Step 5: Is the task registered?
bench execute frappe.utils.scheduler.get_all_tasks

Common Scheduler Failures

# ❌ PROBLEM: Task runs but changes not persisted
def daily_sync():
    for item in frappe.get_all("Item", limit=100):
        frappe.db.set_value("Item", item.name, "synced", 1)
    # MISSING: frappe.db.commit() — ALL changes lost!

# ✅ FIX: ALWAYS commit in scheduler tasks
def daily_sync():
    for item in frappe.get_all("Item", limit=100):
        frappe.db.set_value("Item", item.name, "synced", 1)
    frappe.db.commit()

# ❌ PROBLEM: Task fails silently — no debugging possible
def daily_task():
    try:
        process_records()
    except Exception:
        pass  # Silent death

# ✅ FIX: ALWAYS log errors in scheduler
def daily_task():
    try:
        process_records()
        frappe.db.commit()
    except Exception:
        frappe.log_error(frappe.get_traceback(), "Daily Task Error")

doc_events Errors

Error Handling by Event Phase

Event	Throw Effect	Transaction	Pattern
`validate`	Prevents save, full rollback	Pre-write	Collect errors, throw once
`before_save`	Prevents save, full rollback	Pre-write	Same as validate
`on_update`	Doc already saved, error shown	Post-write	Isolate non-critical ops
`after_insert`	Doc already saved, error shown	Post-write	Isolate non-critical ops
`on_submit`	Doc already submitted	Post-write	Isolate non-critical ops
`on_cancel`	Doc already cancelled	Post-write	Isolate non-critical ops

Multiple Handler Chain Problem

# If App A and App B both register validate for Sales Invoice:
# App A's handler throws → App B's handler NEVER runs

# ✅ ALWAYS be aware: your handler is not alone
def validate(doc, method=None):
    """Collect errors, throw once at end."""
    errors = []
    if doc.grand_total < 0:
        errors.append(_("Total cannot be negative"))
    if errors:
        frappe.throw("<br>".join(errors))

# ✅ For on_update: isolate independent operations
def on_update(doc, method=None):
    try:
        send_notification(doc)
    except Exception:
        frappe.log_error(frappe.get_traceback(), f"Notify error: {doc.name}")
    try:
        sync_external(doc)
    except Exception:
        frappe.log_error(frappe.get_traceback(), f"Sync error: {doc.name}")

NEVER Commit in doc_events

# ❌ BREAKS transaction management
def on_update(doc, method=None):
    frappe.db.set_value("Counter", "main", "count", 100)
    frappe.db.commit()  # Partial commit — dangerous!

# ✅ Framework handles commits automatically
def on_update(doc, method=None):
    frappe.db.set_value("Counter", "main", "count", 100)

Permission Hook Errors

permission_query_conditions: NEVER Throw

# ❌ BREAKS list view entirely
def query_conditions(user):
    if "Sales User" not in frappe.get_roles(user):
        frappe.throw("Access denied")  # LIST VIEW CRASHES
    return f"owner = '{user}'"  # Also: SQL injection!

# ✅ CORRECT — safe fallback, escaped values
def query_conditions(user):
    try:
        user = user or frappe.session.user
        if "System Manager" in frappe.get_roles(user):
            return ""
        return f"`tabSales Invoice`.owner = {frappe.db.escape(user)}"
    except Exception:
        frappe.log_error(frappe.get_traceback(), "Query Conditions Error")
        return f"`tabSales Invoice`.owner = {frappe.db.escape(frappe.session.user)}"

Note: permission_query_conditions only affects frappe.db.get_list(), NOT frappe.db.get_all().

has_permission: NEVER Throw

# ❌ BREAKS document access
def has_permission(doc, user=None, permission_type=None):
    if doc.status == "Locked":
        frappe.throw("Locked")  # DOCUMENT INACCESSIBLE

# ✅ Return False to deny, None to defer
def has_permission(doc, user=None, permission_type=None):
    try:
        user = user or frappe.session.user
        if doc.status == "Locked" and permission_type == "write":
            return False
        return None  # Defer to default permission system
    except Exception:
        frappe.log_error(frappe.get_traceback(), "Permission Error")
        return None

Override & Extend Errors

override_doctype_class: Import Failures

# ❌ COMMON: Import path changes between ERPNext versions
# v14 path:
override_doctype_class = {
    "Sales Invoice": "myapp.overrides.CustomSI"
}
# myapp/overrides.py:
from erpnext.accounts.doctype.sales_invoice.sales_invoice import SalesInvoice
# This path may change in v15/v16!

# ✅ ALWAYS call super(), re-raise validation errors
class CustomSalesInvoice(SalesInvoice):
    def validate(self):
        try:
            super().validate()
        except frappe.ValidationError:
            raise  # ALWAYS re-raise validation errors
        except Exception:
            frappe.log_error(frappe.get_traceback(), "Parent validate error")
            raise
        self.custom_validation()

Warning: Only ONE app's override_doctype_class is active per DocType ("last writer wins"). Use extend_doctype_class [v16+] for multi-app compatibility.

extend_doctype_class [v16+]: Conflicts

# hooks.py
extend_doctype_class = {
    "Sales Invoice": ["myapp.extensions.si.SalesInvoiceMixin"]
}

# ❌ CONFLICT: Two extensions define same method
# App A: class Mixin: def custom_calc(self): ...
# App B: class Mixin: def custom_calc(self): ...
# Result: Last app's method wins silently

# ✅ ALWAYS prefix method names with app name
class SalesInvoiceMixin:
    def myapp_custom_calc(self):
        """Prefixed to avoid conflicts with other extensions."""
        pass

extend_bootinfo Errors

# ❌ BREAKS LOGIN — unhandled error prevents desk from loading
def extend_boot(bootinfo):
    settings = frappe.get_single("My Settings")  # DoesNotExistError!
    bootinfo.config = settings.config

# ✅ ALWAYS wrap in try/except with safe defaults
def extend_boot(bootinfo):
    bootinfo.myapp_config = {}
    try:
        if frappe.db.exists("My Settings", "My Settings"):
            settings = frappe.get_single("My Settings")
            bootinfo.myapp_config = {"feature": settings.feature or False}
    except Exception:
        frappe.log_error(frappe.get_traceback(), "Bootinfo Error")

Fixtures Not Loading

# ❌ WRONG — dt key misspelled
fixtures = [{"doctype": "Custom Field", "filters": [...]}]  # "doctype" not "dt"!

# ✅ CORRECT — use "dt" key
fixtures = [{"dt": "Custom Field", "filters": [["module", "=", "My App"]]}]

# ❌ PROBLEM: DocType doesn't exist on target site
fixtures = [{"dt": "My Custom DocType"}]  # If not created yet → install fails

# ✅ FIX: Ensure DocType is created before fixtures are imported
# Order: DocType JSON → fixtures JSON (install order matters)

Export command: bench --site mysite export-fixtures Import: Automatic during bench --site mysite install-app myapp

Critical Rules

ALWAYS

Restart bench after changing hooks.py
Use try/except in scheduler tasks — no user sees errors
Call frappe.db.commit() in scheduler — no auto-commit
Return safe fallbacks in permission hooks — NEVER throw
Call super() in override classes — re-raise ValidationError
Wrap extend_bootinfo in try/except — errors break login
Wrap wildcard "*" doc_events in try/except — errors break ALL saves
Prefix extend_doctype_class [v16+] methods with app name

NEVER

Throw in permission_query_conditions — breaks list views
Throw in has_permission — breaks document access
Commit in doc_events — breaks transaction management
Import from hooks.py in event handlers — causes circular imports
Assume single handler — multiple apps register doc_events
Use string formatting in permission SQL — SQL injection risk
Ignore scheduler errors — they fail completely silently

Quick Reference: Error Handling by Hook Type

Hook Type	Can Throw?	Commit?	Error Strategy
doc_events (validate)	YES	NEVER	Collect errors, throw once
doc_events (on_update+)	Careful	NEVER	Isolate non-critical ops
scheduler_events	Pointless	ALWAYS	try/except + log_error
permission_query_conditions	NEVER	NEVER	Return "" or owner filter
has_permission	NEVER	NEVER	Return None on error
extend_bootinfo	NEVER	NEVER	try/except + safe defaults
override_doctype_class	YES	NEVER	super() + re-raise
extend_doctype_class [v16+]	YES	NEVER	Prefix methods, avoid conflicts
fixtures	N/A	N/A	Verify dt key and DocType existence
app_include_js/css	N/A	N/A	Check assets/ prefix, run bench build

Reference Files

File	Contents
`references/patterns.md`	Complete error handling patterns by hook type
`references/examples.md`	Full working examples with error handling
`references/anti-patterns.md`	Common mistakes with wrong/correct pairs

frappe-errors-hooks