fix(tests): skip uninstalled doctypes in test record dependency walk

The test runner walks link-field dependencies recursively to pre-generate
test records via `get_missing_records_doctypes`. If any DocType in the
transitive link graph belonged to an app not installed on the test site,
the walk crashed with `DoesNotExistError`, aborting the entire suite
before a single test ran.

Treat such link targets as dead-end leaves instead:

- `get_modules` now returns `(None, None)` when the DocType row does not
  exist, instead of falling through into `load_doctype_module` which
  raises.
- `get_missing_records_doctypes` checks for `module is None`, logs a
  warning naming the parent DocType that linked to it, and returns
  without descending further.

This restores the ability to run downstream test suites that link
(directly or transitively) to optional/uninstalled apps without forcing
every CI environment to know the full transitive link graph.

Fixes #38747

frappe/tests/test_test_utils.py

@@ -1,7 +1,9 @@
+import logging
 from datetime import timedelta
 
 import frappe
 from frappe.tests import IntegrationTestCase
+from frappe.tests.utils.generators import get_missing_records_doctypes, get_modules
 from frappe.utils.data import now_datetime
 
 
@@ -38,6 +40,30 @@ class TestTestUtils(IntegrationTestCase):
 		with self.freeze_time(tomorrow):
 			self.assertEqual(now_datetime(), tomorrow)
 
+	def test_get_modules_returns_none_for_missing_doctype(self):
+		"""DocTypes from uninstalled apps should resolve to (None, None) instead of raising."""
+		get_modules.cache_clear()
+		try:
+			module, test_module = get_modules("Definitely Not A Real DocType")
+		finally:
+			get_modules.cache_clear()
+		self.assertIsNone(module)
+		self.assertIsNone(test_module)
+
+	def test_get_missing_records_doctypes_skips_missing_doctype(self):
+		"""Missing link targets should be skipped with a warning, not crash the walk."""
+		get_modules.cache_clear()
+		try:
+			with self.assertLogs("frappe.testing.generators", level=logging.WARNING) as log_ctx:
+				result = get_missing_records_doctypes("Definitely Not A Real DocType")
+		finally:
+			get_modules.cache_clear()
+		self.assertEqual(result, [])
+		self.assertTrue(
+			any("Definitely Not A Real DocType" in line for line in log_ctx.output),
+			f"Expected warning mentioning the missing doctype, got: {log_ctx.output}",
+		)
+
 
 def tearDownModule():
 	"""assertions for ensuring tests didn't leave state behind"""

frappe/tests/utils/generators.py

@@ -35,9 +35,13 @@ __all__ = [
 
 
 @cache
-def get_modules(doctype) -> tuple[str, ModuleType]:
+def get_modules(doctype) -> tuple[str | None, ModuleType | None]:
 	"""Get the modules for the specified doctype"""
 	module = frappe.db.get_value("DocType", doctype, "module")
+	if not module:
+		# DocType is not installed on this site (e.g. belongs to an uninstalled app);
+		# treat it as a dead-end leaf rather than raising DoesNotExistError.
+		return None, None
 	try:
 		test_module = load_doctype_module(doctype, module, "test_")
 		if test_module:
@@ -49,7 +53,7 @@ def get_modules(doctype) -> tuple[str, ModuleType]:
 
 
 # @cache - don't cache the recursion, code depends on its recurn value declining
-def get_missing_records_doctypes(doctype, visited=None) -> list[str]:
+def get_missing_records_doctypes(doctype, visited=None, _parent=None) -> list[str]:
 	"""Get the dependencies for the specified doctype in a depth-first manner"""
 
 	if visited is None:
@@ -62,7 +66,18 @@ def get_missing_records_doctypes(doctype, visited=None) -> list[str]:
 	# Mark as visited
 	visited.add(doctype)
 
-	_module, test_module = get_modules(doctype)
+	module, test_module = get_modules(doctype)
+	if module is None:
+		# DocType is not installed on this site; skip it instead of crashing the
+		# whole test run. This typically means a Link field points to a DocType
+		# from an optional/uninstalled app.
+		testing_logger.warning(
+			"Skipping test record generation for %r (linked from %r): DocType not installed on this site",
+			doctype,
+			_parent,
+		)
+		return []
+
 	meta = frappe.get_meta(doctype)
 	link_fields = meta.get_link_fields()
 
@@ -79,7 +94,7 @@ def get_missing_records_doctypes(doctype, visited=None) -> list[str]:
 	# Recursive depth-first traversal
 	result = []
 	for dep_doctype in unique_doctypes:
-		result.extend(get_missing_records_doctypes(dep_doctype, visited))
+		result.extend(get_missing_records_doctypes(dep_doctype, visited, _parent=doctype))
 
 	result.append(doctype)
 	return result