From 08e2ad99043fa67ee7dc1a13bde3d915e0ac290f Mon Sep 17 00:00:00 2001
From: Leela vadlamudi <leela@users.noreply.github.com>
Date: Tue, 9 Mar 2021 11:59:17 +0530
Subject: [PATCH] feat: Lazy import functionality added (#12517)

---
 frappe/__init__.py          | 15 +++++++++------
 frappe/utils/lazy_loader.py | 34 ++++++++++++++++++++++++++++++++++
 2 files changed, 43 insertions(+), 6 deletions(-)
 create mode 100644 frappe/utils/lazy_loader.py

diff --git a/frappe/__init__.py b/frappe/__init__.py
index 160ed93c50..ab27bff9fe 100644
--- a/frappe/__init__.py
+++ b/frappe/__init__.py
@@ -18,9 +18,14 @@ import os, sys, importlib, inspect, json
 from past.builtins import cmp
 import click
 
-# public
+# Local application imports
 from .exceptions import *
 from .utils.jinja import (get_jenv, get_template, render_template, get_email_from_template, get_jloader)
+from .utils.lazy_loader import lazy_import
+
+# Lazy imports
+faker = lazy_import('faker')
+
 
 # Harmless for Python 3
 # For Python 2 set default encoding to utf-8
@@ -1749,15 +1754,13 @@ def parse_json(val):
 	return parse_json(val)
 
 def mock(type, size=1, locale='en'):
-	from faker import Faker
-
 	results = []
-	faker = Faker(locale)
-	if not type in dir(faker):
+	fake = faker.Faker(locale)
+	if type not in dir(fake):
 		raise ValueError('Not a valid mock type.')
 	else:
 		for i in range(size):
-			data = getattr(faker, type)()
+			data = getattr(fake, type)()
 			results.append(data)
 
 	from frappe.chat.util import squashify
diff --git a/frappe/utils/lazy_loader.py b/frappe/utils/lazy_loader.py
new file mode 100644
index 0000000000..ae4cba66a1
--- /dev/null
+++ b/frappe/utils/lazy_loader.py
@@ -0,0 +1,34 @@
+import importlib.util
+import sys
+
+def lazy_import(name, package=None):
+	"""Import a module lazily.
+
+	The module is loaded when modules's attribute is accessed for the first time.
+	This works with both absolute and relative imports.
+	$ cat mod.py
+	print("Loading mod.py")
+	$ python -i lazy_loader.py
+	>>> mod = lazy_import("mod") # Module is not loaded
+	>>> mod.__str__() # module is loaded on accessing attribute
+	Loading mod.py
+	"<module 'mod' from '.../frappe/utils/mod.py'>"
+	>>>
+
+	Code based on https://github.com/python/cpython/blob/master/Doc/library/importlib.rst#implementing-lazy-imports.
+	"""
+	# Return if the module already loaded
+	if name in sys.modules:
+		return sys.modules[name]
+
+	# Find the spec if not loaded
+	spec = importlib.util.find_spec(name, package)
+	if not spec:
+		raise ImportError(f'Module {name} Not found.')
+
+	loader = importlib.util.LazyLoader(spec.loader)
+	spec.loader = loader
+	module = importlib.util.module_from_spec(spec)
+	sys.modules[name] = module
+	loader.exec_module(module)
+	return module