Fix various Sphinx warnings

docs/README.rst

-.. _swh-loader-core:
-
 Software Heritage - Loader foundations
 ======================================
 

docs/index.rst

+.. _swh-loader-core:
+
 .. include:: README.rst
 
 .. toctree::
@@ -16,3 +18,4 @@ Reference Documentation
 
    cli
    /apidoc/swh.loader.core
+   /apidoc/swh.loader.package

docs/package-loader-tutorial.rst

@@ -71,7 +71,7 @@ Create a file named ``loader.py`` in your package's directory, with two empty cl
 
 
 We now have to fill some of the methods declared by
-:ref:class:`swh.loader.package.PackageLoader`: in your new ``NewLoader`` class.
+:class:`swh.loader.package.PackageLoader`: in your new ``NewLoader`` class.
 
 
 Listing versions
@@ -599,7 +599,7 @@ a date of discovery (usually the time your loader ran).
 
 This is done by adding them to the ``directory_extrinsic_metadata`` attribute of
 your ``NewPackageInfo`` object when creating it in ``get_package_info``
-as :py:cls:`swh.loader.package.loader.RawExtrinsicMetadataCore` objects::
+as :class:`swh.loader.package.loader.RawExtrinsicMetadataCore` objects::
 
    NewPackageInfo(
        ...,
@@ -615,7 +615,7 @@ as :py:cls:`swh.loader.package.loader.RawExtrinsicMetadataCore` objects::
 ``format`` should be a human-readable ASCII string that unambiguously describes
 the format. Readers of the metadata object will have a built-in list of formats
 they understand, and will check if your metadata object is among them.
-You should use one of the :ref:`known metadata formats <extrinsic-metadata-format>`
+You should use one of the :ref:`known metadata formats <extrinsic-metadata-formats>`
 if possible, or add yours to this list.
 
 ``metadata`` is the metadata object itself. When possible, it should be copied verbatim

docs/vcs-loader-overview.rst

@@ -90,7 +90,7 @@ locally, then return them lazily on demand.
 
 
 Incremental loading
-------------------
+-------------------
 
 Loading a repository from scratch can be costly, so ``swh-storage`` provides
 ways to remember what objects in the repository were already loaded,

swh/loader/core/loader.py

@@ -55,6 +55,11 @@ class BaseLoader:
 
     """
 
+    visit_date: Optional[datetime.datetime]
+    origin: Optional[Origin]
+    origin_metadata: Dict[str, Any]
+    loaded_snapshot_id: Optional[Sha1Git]
+
     def __init__(
         self,
         storage: StorageInterface,
@@ -77,14 +82,14 @@ class BaseLoader:
         _log.setLevel(logging.WARN)
 
         # possibly overridden in self.prepare method
-        self.visit_date: Optional[datetime.datetime] = None
-        self.origin: Optional[Origin] = None
+        self.visit_date = None
+        self.origin = None
 
         if not hasattr(self, "visit_type"):
             self.visit_type: Optional[str] = None
 
-        self.origin_metadata: Dict[str, Any] = {}
-        self.loaded_snapshot_id: Optional[Sha1Git] = None
+        self.origin_metadata = {}
+        self.loaded_snapshot_id = None
 
         if save_data_path:
             path = save_data_path

swh/loader/core/utils.py

@@ -18,9 +18,9 @@ def clean_dangling_folders(dirpath, pattern_check, log=None):
     Args:
         dirpath (str): Path to check for dangling files
         pattern_check (str): A dedicated pattern to check on first
-        level directory (e.g `swh.loader.mercurial.`,
-        `swh.loader.svn.`)
-        log (Logger): Optional logger
+            level directory (e.g `swh.loader.mercurial.`,
+            `swh.loader.svn.`)
+            log (Logger): Optional logger
 
     """
     if not os.path.exists(dirpath):

swh/loader/package/loader.py

@@ -75,7 +75,7 @@ of downloaded archive files."""
 
 
 PartialExtID = Tuple[str, bytes]
-"""The ``extid_type`` and ``extid`` fields of an :ref:py:`ExtID` object."""
+"""The ``extid_type`` and ``extid`` fields of an :class:`ExtID` object."""
 
 
 @attr.s
@@ -170,7 +170,7 @@ class PackageLoader(BaseLoader, Generic[TPackageInfo]):
         """Return the list of all published package versions.
 
         Raises:
-           `class:swh.loader.exception.NotFound` error when failing to read the
+           class:`swh.loader.exception.NotFound` error when failing to read the
             published package versions.
 
         Returns: