Fixed #21581 -- Fixed a number of issues with collectstatic.

When STATIC_ROOT wasn't set, collectstatic --clear would delete
every files within the current directory and its descendants.

This patch makes the following changes:

Prevent collectstatic from running if STATIC_ROOT isn't set.

Fixed an issue that prevented collectstatic from displaying the
destination directory.

Changed the warning header to notify when the command is run
in dry-run mode.

3 files changed, 28 insertions, 25 deletions

diff --git a/django/conf/global_settings.py b/django/conf/global_settings.py
index d29dd5ec34..d86a4272cd 100644
--- a/django/conf/global_settings.py
+++ b/django/conf/global_settings.py
@@ -290,7 +290,7 @@ MEDIA_URL = ''
 
 # Absolute path to the directory static files should be collected to.
 # Example: "/var/www/example.com/static/"
-STATIC_ROOT = ''
+STATIC_ROOT = None
 
 # URL that handles the static files served from STATIC_ROOT.
 # Example: "http://example.com/static/", "http://static.example.com/"
diff --git a/django/contrib/staticfiles/management/commands/collectstatic.py b/django/contrib/staticfiles/management/commands/collectstatic.py
index 67fa6229c4..9009b82c67 100644
--- a/django/contrib/staticfiles/management/commands/collectstatic.py
+++ b/django/contrib/staticfiles/management/commands/collectstatic.py
@@ -137,32 +137,38 @@ class Command(NoArgsCommand):
 
     def handle_noargs(self, **options):
         self.set_options(**options)
-        # Warn before doing anything more.
-        if (isinstance(self.storage, FileSystemStorage) and
+
+        message = ['\n']
+        if self.dry_run:
+            message.append(
+                'You have activated the --dry-run option so no files will be modified.\n\n'
+            )
+
+        message.append(
+            'You have requested to collect static files at the destination\n'
+            'location as specified in your settings'
+        )
+
+        if (isinstance(self.storage._wrapped, FileSystemStorage) and
                 self.storage.location):
             destination_path = self.storage.location
-            destination_display = ':\n\n    %s' % destination_path
+            message.append(':\n\n    %s\n\n' % destination_path)
         else:
             destination_path = None
-            destination_display = '.'
+            message.append('.\n\n')
 
         if self.clear:
-            clear_display = 'This will DELETE EXISTING FILES!'
+            message.append('This will DELETE EXISTING FILES!\n')
         else:
-            clear_display = 'This will overwrite existing files!'
-
-        if self.interactive:
-            confirm = input("""
-You have requested to collect static files at the destination
-location as specified in your settings%s
+            message.append('This will overwrite existing files!\n')
 
-%s
-Are you sure you want to do this?
+        message.append(
+            'Are you sure you want to do this?\n\n'
+            "Type 'yes' to continue, or 'no' to cancel: "
+        )
 
-Type 'yes' to continue, or 'no' to cancel: """
-% (destination_display, clear_display))
-            if confirm != 'yes':
-                raise CommandError("Collecting static files cancelled.")
+        if self.interactive and input(''.join(message)) != 'yes':
+            raise CommandError("Collecting static files cancelled.")
 
         collected = self.collect()
         modified_count = len(collected['modified'])
diff --git a/django/contrib/staticfiles/storage.py b/django/contrib/staticfiles/storage.py
index 5190a299e4..b5d05aa6b2 100644
--- a/django/contrib/staticfiles/storage.py
+++ b/django/contrib/staticfiles/storage.py
@@ -32,16 +32,13 @@ class StaticFilesStorage(FileSystemStorage):
             location = settings.STATIC_ROOT
         if base_url is None:
             base_url = settings.STATIC_URL
-        check_settings(base_url)
-        super(StaticFilesStorage, self).__init__(location, base_url,
-                                                 *args, **kwargs)
-
-    def path(self, name):
-        if not self.location:
+        if not location:
             raise ImproperlyConfigured("You're using the staticfiles app "
                                        "without having set the STATIC_ROOT "
                                        "setting to a filesystem path.")
-        return super(StaticFilesStorage, self).path(name)
+        check_settings(base_url)
+        super(StaticFilesStorage, self).__init__(location, base_url,
+                                                 *args, **kwargs)
 
 
 class CachedFilesMixin(object):