Remove old folder for conan install (#5376)

conans/client/conf/config_installer.py

@@ -37,6 +37,7 @@ def tmp_config_install_folder(cache):
     tmp_folder = os.path.join(cache.cache_folder, "tmp_config_install")
     # necessary for Mac OSX, where the temp folders in /var/ are symlinks to /private/var/
     tmp_folder = os.path.realpath(tmp_folder)
+    rmdir(tmp_folder)
     mkdir(tmp_folder)
     try:
         yield tmp_folder

conans/test/unittests/client/conf/config_installer/test_install_folder.py

@@ -0,0 +1,25 @@
+# coding=utf-8
+
+import unittest
+import os
+
+from conans.client.conf.config_installer import tmp_config_install_folder
+from conans.test.utils.tools import TestClient
+
+
+class InstallFolderTests(unittest.TestCase):
+
+    def test_unique_install_folder(self):
+        """ Validate if tmp_config_install_folder is removing old folder before creating a new one
+
+        tmp_config_install_folder must create the same folder, but all items must be exclude when a
+        new folder is created.
+        """
+        client = TestClient()
+
+        with tmp_config_install_folder(client.cache) as tmp_folder_first:
+            temp_file = os.path.join(tmp_folder_first, "foobar.txt")
+            open(temp_file, "w+")
+            with tmp_config_install_folder(client.cache) as tmp_folder_second:
+                self.assertEqual(tmp_folder_first, tmp_folder_second)
+                self.assertFalse(os.path.exists(temp_file))