NF: Factory function to get Repo instances from a path

datalad/core/local/repo.py

@@ -0,0 +1,73 @@
+# emacs: -*- mode: python; py-indent-offset: 4; tab-width: 4; indent-tabs-mode: nil -*-
+# ex: set sts=4 ts=4 sw=4 noet:
+# ## ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ##
+#
+#   See COPYING file distributed along with the datalad package for the
+#   copyright and license terms.
+#
+# ## ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ### ##
+""" Core repository-related functionality
+
+"""
+
+from datalad.support.exceptions import (
+    InvalidGitRepositoryError,
+    InvalidAnnexRepositoryError,
+    NoSuchPathError,
+)
+
+import logging
+lgr = logging.getLogger('datalad.core.local.repo')
+
+__all__ = ["repo_from_path"]
+
+
+def repo_from_path(path):
+    """Get a Repo instance from a path.
+
+    Parameters
+    ----------
+    path : path-like
+      Root path of the repository.
+
+    Returns
+    -------
+    Repo
+      Repo instance matching the type of the repository at path.
+
+    Raises
+    ------
+    ValueError
+      If no repository could be found at the path, or if its type could not
+      be determined.
+    """
+    # keep the imports local for now until it is clearer what the module setup
+    # will be
+    from datalad.support.gitrepo import GitRepo
+    from datalad.support.annexrepo import AnnexRepo
+
+    repo = None
+    for cls, ckw, kw in (
+            # Non-initialized is okay. We want to figure the correct instance
+            # to represent what's there - that's it.
+            (AnnexRepo, {'allow_noninitialized': True}, {'init': False}),
+            (GitRepo, {}, {})
+    ):
+        if not cls.is_valid_repo(path, **ckw):
+            continue
+
+        try:
+            lgr.log(5, "Detected %s at %s", cls, path)
+            repo = cls(path, create=False, **kw)
+            break
+        except (InvalidGitRepositoryError, NoSuchPathError,
+                InvalidAnnexRepositoryError) as exc:
+            lgr.log(
+                5,
+                "Ignore exception after inappropriate repository type guess: "
+                "%s", exc)
+
+    if repo is None:
+        raise ValueError('No repository at {}'.format(path))
+
+    return repo

datalad/distribution/dataset.py

@@ -22,23 +22,19 @@
 
 from datalad import cfg
 from datalad.config import ConfigManager
-from datalad.dochelpers import exc_str
+from datalad.core.local.repo import repo_from_path
 from datalad.support.annexrepo import AnnexRepo
 from datalad.support.constraints import Constraint
 # DueCredit
 from datalad.support.due import due
 from datalad.support.due_utils import duecredit_dataset
 from datalad.support.exceptions import (
-    InvalidAnnexRepositoryError,
-    InvalidGitRepositoryError,
     NoDatasetArgumentFound,
-    NoSuchPathError,
 )
 from datalad.support.gitrepo import (
     GitRepo,
 )
 from datalad.support.repo import PathBasedFlyweight
-from datalad.support.network import RI
 from datalad.support import path as op
 
 import datalad.utils as ut
@@ -284,34 +280,16 @@ def repo(self):
         # be the last reference, which would lead to those objects being
         # destroyed and therefore the constructor call would result in an
         # actually new instance. This is unnecessarily costly.
-        valid = False
-        for cls, ckw, kw in (
-                # Non-initialized is okay. We want to figure the correct instance to represent what's there - that's it.
-                (AnnexRepo, {'allow_noninitialized': True}, {'init': False}),
-                (GitRepo, {}, {})
-        ):
-            if cls.is_valid_repo(self._path, **ckw):
-                try:
-                    lgr.log(5, "Detected %s at %s", cls, self._path)
-                    self._repo = cls(self._path, create=False, **kw)
-                    valid = True
-                    break
-                except (InvalidGitRepositoryError, NoSuchPathError,
-                        InvalidAnnexRepositoryError) as exc:
-                    lgr.log(5,
-                            "Oops -- guess on repo type was wrong?: %s",
-                            exc_str(exc))
-
-        if not valid:
+        try:
+            self._repo = repo_from_path(self._path)
+        except ValueError:
+            lgr.log(5, "Failed to detect a valid repo at %s", self.path)
             self._repo = None
+            return
 
-        if self._repo is None:
-            # Often .repo is requested to 'sense' if anything is installed
-            # under, and if so -- to proceed forward. Thus log here only
-            # at DEBUG level and if necessary "complaint upstairs"
-            lgr.log(5, "Failed to detect a valid repo at %s", self.path)
-        elif due.active:
-            # TODO: Figure out, when exactly this is needed. Don't think it makes sense to do this for every dataset,
+        if due.active:
+            # TODO: Figure out, when exactly this is needed. Don't think it
+            #       makes sense to do this for every dataset,
             #       no matter what => we want .repo to be as cheap as it gets.
             # Makes sense only on installed dataset - @never_fail'ed
             duecredit_dataset(self)