raise error when symlink already exists but points to a different path, and add test for it

Author: migueldiascosta

easybuild/tools/filetools.py

@@ -298,7 +298,12 @@ def symlink(source_path, symlink_path, use_abspath_source=True):
     if use_abspath_source:
         source_path = os.path.abspath(source_path)
 
-    if os.path.exists(symlink_path) and os.path.abspath(source_path) == os.path.abspath(os.readlink(symlink_path)):
+    if os.path.exists(symlink_path):
+        abs_source_path = os.path.abspath(source_path)
+        symlink_target_path = os.path.abspath(os.readlink(symlink_path))
+        if abs_source_path != symlink_target_path:
+            raise EasyBuildError("Trying to symlink %s to %s, but the symlink already exists and points to %s.",
+                                 source_path, symlink_path, symlink_target_path)
         _log.info("Skipping symlinking %s to %s, link already exists", source_path, symlink_path)
     else:
         try:

test/framework/filetools.py

@@ -574,6 +574,17 @@ def test_symlink_resolve_path(self):
 
         self.assertTrue(os.path.samefile(os.path.join(self.test_prefix, 'test', 'test.txt'), link))
 
+        # test symlink when it already exists and points to the same path
+        ft.symlink(test_file, link)
+
+        # test symlink when it already exists but points to a different path
+        test_file2 = os.path.join(link_dir, 'test2.txt')
+        ft.write_file(test_file, "test123")
+        self.assertErrorRegex(EasyBuildError,
+                              "Trying to symlink %s to %s, but the symlink already exists and points to %s." %
+                              (test_file2, link, test_file),
+                              ft.symlink, test_file2, link)
+
         # test resolve_path
         self.assertEqual(test_dir, ft.resolve_path(link_dir))
         self.assertEqual(os.path.join(os.path.realpath(self.test_prefix), 'test', 'test.txt'), ft.resolve_path(link))