From 7e4677df4a9925a516e7e674f65d76a56d31a75c Mon Sep 17 00:00:00 2001
From: Mykola Kokalko <jajcee@gmail.com>
Date: Sun, 3 Feb 2019 15:24:48 +0200
Subject: [PATCH] Fixed #29529 -- FilePathField path parameter now accepts a
 callable.

---
 django/db/models/fields/__init__.py      |  2 +-
 docs/ref/models/fields.txt               | 13 ++++++++++++
 tests/model_fields/test_filepathfield.py | 26 ++++++++++++++++++++++++
 3 files changed, 40 insertions(+), 1 deletion(-)
 create mode 100644 tests/model_fields/test_filepathfield.py

diff --git a/django/db/models/fields/__init__.py b/django/db/models/fields/__init__.py
index f32ce6462964d..dbe4031cf019b 100644
--- a/django/db/models/fields/__init__.py
+++ b/django/db/models/fields/__init__.py
@@ -1712,7 +1712,7 @@ def get_prep_value(self, value):
 
     def formfield(self, **kwargs):
         return super().formfield(**{
-            'path': self.path,
+            'path': self.path() if callable(self.path) else self.path,
             'match': self.match,
             'recursive': self.recursive,
             'form_class': forms.FilePathField,
diff --git a/docs/ref/models/fields.txt b/docs/ref/models/fields.txt
index 1b572d8076cb0..c9a22ad273c36 100644
--- a/docs/ref/models/fields.txt
+++ b/docs/ref/models/fields.txt
@@ -868,6 +868,19 @@ directory on the filesystem. Has three special arguments, of which the first is
     Required. The absolute filesystem path to a directory from which this
     :class:`FilePathField` should get its choices. Example: ``"/home/images"``.
 
+    A callable (such as a function) can also be passed to dynamically set the
+    path at runtime::
+
+         def generate_path():
+            return os.path.join(settings.LOCAL_FILE_DIR, '/images')
+
+         file = models.FilePathField(path=generate_path)
+
+    .. versionchanged:: 3.0
+
+         Older versions don't allow passing a callable.
+
+
 .. attribute:: FilePathField.match
 
     Optional. A regular expression, as a string, that :class:`FilePathField`
diff --git a/tests/model_fields/test_filepathfield.py b/tests/model_fields/test_filepathfield.py
new file mode 100644
index 0000000000000..a6fdccdce5709
--- /dev/null
+++ b/tests/model_fields/test_filepathfield.py
@@ -0,0 +1,26 @@
+import os.path
+
+from django.db.models import FilePathField
+from django.test import TestCase
+
+PATH = os.path.dirname(os.path.abspath(__file__))
+
+
+def generate_path():
+    return PATH
+
+
+class FilePathFieldTests(TestCase):
+
+    def test_string(self):
+        fp = FilePathField(path=PATH)
+        self.assertEqual(PATH, fp.path)
+
+    def test_callable(self):
+        fp = FilePathField(path=generate_path)
+        self.assertEqual(PATH, fp.path())
+
+    def test_formfield(self):
+        fp = FilePathField(path=generate_path)
+        formfield = fp.formfield()
+        self.assertEqual(formfield.path, PATH)