From ef082ebb84f00e38af4e8880d04e8365c2766d34 Mon Sep 17 00:00:00 2001
From: Mykola Kokalko <jajcee@gmail.com>
Date: Thu, 2 May 2019 10:42:10 +0200
Subject: [PATCH] Fixed #29529 -- Allowed models.fields.FilePathField to accept
 a callable path.

---
 django/db/models/fields/__init__.py      |  2 +-
 docs/ref/models/fields.txt               | 17 +++++++++++++++++
 docs/releases/3.0.txt                    |  2 ++
 tests/model_fields/test_filepathfield.py | 10 ++++++++++
 4 files changed, 30 insertions(+), 1 deletion(-)

diff --git a/django/db/models/fields/__init__.py b/django/db/models/fields/__init__.py
index 0c64748ccd..4d7eb11151 100644
--- a/django/db/models/fields/__init__.py
+++ b/django/db/models/fields/__init__.py
@@ -1709,7 +1709,7 @@ class FilePathField(Field):
 
     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 e352e8b007..fbcba2bd66 100644
--- a/docs/ref/models/fields.txt
+++ b/docs/ref/models/fields.txt
@@ -868,6 +868,23 @@ 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"``.
 
+    ``path`` may also be a callable, such as a function to dynamically set the
+    path at runtime. Example::
+
+        import os
+        from django.conf import settings
+        from django.db import models
+
+        def images_path():
+            return os.path.join(settings.LOCAL_FILE_DIR, 'images')
+
+        class MyModel(models.Model):
+            file = models.FilePathField(path=images_path)
+
+    .. versionchanged:: 3.0
+
+        ``path`` can now be a callable.
+
 .. attribute:: FilePathField.match
 
     Optional. A regular expression, as a string, that :class:`FilePathField`
diff --git a/docs/releases/3.0.txt b/docs/releases/3.0.txt
index b78d4bd6ab..966644385b 100644
--- a/docs/releases/3.0.txt
+++ b/docs/releases/3.0.txt
@@ -206,6 +206,8 @@ Models
 
 * ``connection.queries`` now shows ``COPY … TO`` statements on PostgreSQL.
 
+* :class:`~django.db.models.FilePathField` now accepts a callable ``path``.
+
 Requests and Responses
 ~~~~~~~~~~~~~~~~~~~~~~
 
diff --git a/tests/model_fields/test_filepathfield.py b/tests/model_fields/test_filepathfield.py
index d5d43ff6f6..362d12d0db 100644
--- a/tests/model_fields/test_filepathfield.py
+++ b/tests/model_fields/test_filepathfield.py
@@ -10,3 +10,13 @@ class FilePathFieldTests(SimpleTestCase):
         field = FilePathField(path=path)
         self.assertEqual(field.path, path)
         self.assertEqual(field.formfield().path, path)
+
+    def test_callable_path(self):
+        path = os.path.dirname(__file__)
+
+        def generate_path():
+            return path
+
+        field = FilePathField(path=generate_path)
+        self.assertEqual(field.path(), path)
+        self.assertEqual(field.formfield().path, path)