dvc: add sanity checks for hard/symlinks

dvc/command/version.py

@@ -86,9 +86,9 @@ def get_fs_type(path):
     @staticmethod
     def get_linktype_support_info(repo):
         links = {
-            "reflink": System.reflink,
-            "hardlink": System.hardlink,
-            "symlink": System.symlink,
+            "reflink": (System.reflink, None),
+            "hardlink": (System.hardlink, System.is_hardlink),
+            "symlink": (System.symlink, System.is_symlink),
         }
 
         fname = "." + str(uuid.uuid4())
@@ -98,18 +98,16 @@ def get_linktype_support_info(repo):
 
         cache = []
 
-        for name, link in links.items():
+        for name, (link, is_link) in links.items():
             try:
                 link(src, dst)
+                status = "supported"
+                if is_link and not is_link(dst):
+                    status = "broken"
                 os.unlink(dst)
-                supported = True
             except DvcException:
-                supported = False
-            cache.append(
-                "{name} - {supported}".format(
-                    name=name, supported=True if supported else False
-                )
-            )
+                status = "not supported"
+            cache.append("{name} - {status}".format(name=name, status=status))
         os.remove(src)
 
         return ", ".join(cache)

dvc/remote/base.py

@@ -392,13 +392,24 @@ def _link(self, from_info, to_info, link_types):
 
         self._try_links(from_info, to_info, link_types)
 
+    def _verify_link(self, path_info, link_type):
+        if self.cache_type_confirmed:
+            return
+
+        is_link = getattr(self, "is_{}".format(link_type), None)
+        if is_link and not is_link(path_info):
+            self.remove(path_info)
+            raise DvcException("failed to verify {}".format(link_type))
+
+        self.cache_type_confirmed = True
+
     @slow_link_guard
     def _try_links(self, from_info, to_info, link_types):
         while link_types:
             link_method = getattr(self, link_types[0])
             try:
                 self._do_link(from_info, to_info, link_method)
-                self.cache_type_confirmed = True
+                self._verify_link(to_info, link_types[0])
                 return
 
             except DvcException as exc:

dvc/remote/local.py

@@ -178,6 +178,10 @@ def copy(self, from_info, to_info):
     def symlink(from_info, to_info):
         System.symlink(from_info, to_info)
 
+    @staticmethod
+    def is_symlink(path_info):
+        return System.is_symlink(path_info)
+
     def hardlink(self, from_info, to_info):
         # If there are a lot of empty files (which happens a lot in datasets),
         # and the cache type is `hardlink`, we might reach link limits and
@@ -204,6 +208,10 @@ def hardlink(self, from_info, to_info):
 
         System.hardlink(from_info, to_info)
 
+    @staticmethod
+    def is_hardlink(path_info):
+        return System.is_hardlink(path_info)
+
     @staticmethod
     def reflink(from_info, to_info):
         System.reflink(from_info, to_info)

tests/func/test_version.py

@@ -17,7 +17,9 @@ def test_info_in_repo(tmp_dir, dvc, caplog):
     assert re.search(r"Platform: .*", caplog.text)
     assert re.search(r"Binary: (True|False)", caplog.text)
     assert re.search(r"Package: .*", caplog.text)
-    assert re.search(r"(Cache: (.*link - (True|False)(,\s)?){3})", caplog.text)
+    assert re.search(
+        r"(Cache: (.*link - (not )?supported(,\s)?){3})", caplog.text
+    )
 
 
 @pytest.mark.skipif(psutil is None, reason="No psutil.")
@@ -37,9 +39,7 @@ def test_info_outside_of_repo(tmp_dir, caplog):
     assert re.search(r"Platform: .*", caplog.text)
     assert re.search(r"Binary: (True|False)", caplog.text)
     assert re.search(r"Package: .*", caplog.text)
-    assert not re.search(
-        r"(Cache: (.*link - (True|False)(,\s)?){3})", caplog.text
-    )
+    assert not re.search(r"(Cache: (.*link - (not )?(,\s)?){3})", caplog.text)
 
 
 @pytest.mark.skipif(psutil is None, reason="No psutil.")