Fix filesystem serialisation to avoid connection

src/pytroll_watchers/local_watcher.py

@@ -1,6 +1,22 @@
 """Watcher for non-remote file systems.
 
 Either using OS-based envents (like inotify on linux), or polling.
+
+An example configuration file to retrieve data from a directory.
+
+.. code-block:: yaml
+
+  backend: local
+  fs_config:
+    directory: /data
+    file pattern: "H-000-{orig_platform_name:4s}__-{orig_platform_name:4s}_{service:3s}____-{channel_name:_<9s}-\
+        {segment:_<9s}-{start_time:%Y%m%d%H%M}-{compression:1s}_"
+  publisher_config:
+    name: hrit_watcher
+  message_config:
+    subject: /segment/hrit/l1b/
+    atype: file
+
 """
 import logging
 import os

src/pytroll_watchers/publisher.py

@@ -3,9 +3,10 @@
 import datetime
 import json
 import logging
-from contextlib import closing, suppress
+from contextlib import closing, contextmanager, suppress
 from copy import deepcopy
 
+import fsspec
 from posttroll.message import Message
 from posttroll.publisher import create_publisher_from_dict_config
 from trollsift import parse
@@ -104,12 +105,37 @@ def _build_file_location(file_item, include_dir=None):
     else:
         uid = file_item.name
     file_location["uid"] = uid
-    with suppress(AttributeError):
-        file_location["filesystem"] = json.loads(file_item.fs.to_json())
+    with suppress(AttributeError):  # fileitem is not a UPath if it cannot access .fs
+        with dummy_connect(file_item):
+            file_location["filesystem"] = json.loads(file_item.fs.to_json(include_password=False))
+
         file_location["path"] = file_item.path
+
     return file_location
 
 
+@contextmanager
+def dummy_connect(file_item):
+    """Make the _connect method of the fsspec class a no-op.
+
+    This is for the case where only serialization of the filesystem is needed.
+    """
+    def _fake_connect(*_args, **_kwargs): ...
+
+    klass = fsspec.get_filesystem_class(file_item.protocol)
+    try:
+        original_connect = klass._connect
+    except AttributeError:
+        yield
+        return
+
+    klass._connect = _fake_connect
+    try:
+        yield
+    finally:
+        klass._connect = original_connect
+
+
 def apply_aliases(aliases, metadata):
     """Apply aliases to the metadata.
 

tests/test_local_watcher.py

@@ -118,3 +118,25 @@ def test_publish_paths_forbids_passing_password(tmp_path, patched_local_events,
                 local_watcher.file_publisher(fs_config=local_settings,
                                              publisher_config=publisher_settings,
                                              message_config=message_settings)
+
+
+def test_publish_paths_with_ssh(tmp_path, patched_local_events):  # noqa
+    """Test publishing paths with an ssh protocol."""
+    filename = os.fspath(tmp_path / "foo.txt")
+
+    host = "localhost"
+
+    local_settings = dict(directory=tmp_path, protocol="ssh",
+                          storage_options=dict(host=host))
+    publisher_settings = dict(nameservers=False, port=1979)
+    message_settings = dict(subject="/segment/viirs/l1b/", atype="file", data=dict(sensor="viirs"))
+
+    with patched_local_events([filename]):
+        with patched_publisher() as published_messages:
+            local_watcher.file_publisher(fs_config=local_settings,
+                                         publisher_config=publisher_settings,
+                                         message_config=message_settings)
+            assert len(published_messages) == 1
+            message = Message(rawstr=published_messages[0])
+            assert message.data["uri"].startswith("ssh://")
+            assert message.data["filesystem"]["host"] == host