From 5d63bf0bc338840cfbb10f3528cc5b5ca3170f9b Mon Sep 17 00:00:00 2001
From: pablo <paul@eclipse-online.com>
Date: Thu, 26 Sep 2019 12:05:32 -0700
Subject: [PATCH] [3.0.x] Fixed #30802 -- Prevented manifest creation when
 running collectstatic in dry run mode.

Backport of fa8fe09e4e2b538c5d50a559081861d5c0635d55 from master
---
 django/contrib/staticfiles/storage.py      | 3 ++-
 tests/staticfiles_tests/test_management.py | 5 +++++
 2 files changed, 7 insertions(+), 1 deletion(-)

diff --git a/django/contrib/staticfiles/storage.py b/django/contrib/staticfiles/storage.py
index 607c11b7d6f..33b2f0d1fb0 100644
--- a/django/contrib/staticfiles/storage.py
+++ b/django/contrib/staticfiles/storage.py
@@ -403,7 +403,8 @@ class ManifestFilesMixin(HashedFilesMixin):
     def post_process(self, *args, **kwargs):
         self.hashed_files = {}
         yield from super().post_process(*args, **kwargs)
-        self.save_manifest()
+        if not kwargs.get('dry_run'):
+            self.save_manifest()
 
     def save_manifest(self):
         payload = {'paths': self.hashed_files, 'version': self.manifest_version}
diff --git a/tests/staticfiles_tests/test_management.py b/tests/staticfiles_tests/test_management.py
index c89240915b9..7630efbd9b7 100644
--- a/tests/staticfiles_tests/test_management.py
+++ b/tests/staticfiles_tests/test_management.py
@@ -334,6 +334,11 @@ class TestCollectionDryRun(TestNoFilesCreated, CollectionTestCase):
         super().run_collectstatic(dry_run=True)
 
 
+@override_settings(STATICFILES_STORAGE='django.contrib.staticfiles.storage.ManifestStaticFilesStorage')
+class TestCollectionDryRunManifestStaticFilesStorage(TestCollectionDryRun):
+    pass
+
+
 class TestCollectionFilesOverride(CollectionTestCase):
     """
     Test overriding duplicated files by ``collectstatic`` management command.