Make RequestsFetcher public

This is useful for those who want to use the default fetcher
but modify some attributes

The file itself could be moved to tuf/ngclient/ but this is not done yet
as sigstore-python is using this internal module. Move can be done once
sigstore-python 1.0 is no longer relevant.

Fixes #2268

Signed-off-by: Jussi Kukkonen <jkukkonen@google.com>

Author: jku

tests/test_fetcher_ng.py

@@ -20,7 +20,7 @@
 
 from tests import utils
 from tuf.api import exceptions
-from tuf.ngclient._internal.requests_fetcher import RequestsFetcher
+from tuf.ngclient import RequestsFetcher
 
 logger = logging.getLogger(__name__)
 

tuf/ngclient/__init__.py

@@ -4,12 +4,18 @@
 """TUF client public API
 """
 
+
+# requests_fetcher is public but comes from _internal for now (because
+# sigstore-python 1.0 still uses the module from there). requests_fetcher
+# can be moved out of _internal once sigstore-python 1.0 is not relevant.
+from tuf.ngclient._internal.requests_fetcher import RequestsFetcher
 from tuf.ngclient.config import UpdaterConfig
 from tuf.ngclient.fetcher import FetcherInterface
 from tuf.ngclient.updater import Updater
 
 __all__ = [
     FetcherInterface.__name__,
+    RequestsFetcher.__name__,
     Updater.__name__,
     UpdaterConfig.__name__,
 ]

tuf/ngclient/_internal/requests_fetcher.py

@@ -24,8 +24,10 @@ class RequestsFetcher(FetcherInterface):
     """An implementation of ``FetcherInterface`` based on the requests library.
 
     Attributes:
-        _sessions: Dictionary of ``Requests.Session`` objects storing a separate
-            session per scheme+hostname combination.
+        socket_timeout: Timeout in seconds, used for both initial connection
+            delay and the maximum delay between bytes received. Default is
+            4 seconds.
+        chunk_size: Chunk size in bytes used when downloading.
     """
 
     def __init__(self) -> None: