Add a check for calling with an existing member

pooch/processors.py

@@ -95,7 +95,13 @@ def __call__(self, fname, action, pooch):
         else:
             archive_dir = fname.rsplit(os.path.sep, maxsplit=1)[0]
             self.extract_dir = os.path.join(archive_dir, self.extract_dir)
-        members = self.members or self._all_members(fname)
+        # Get a list of everyone who is supposed to be in the unpacked folder
+        # so we can check if they are all there or if we need to extract new
+        # files.
+        if self.members is None or not self.members:
+            members = self._all_members(fname)
+        else:
+            members = self.members
         if (
             (action in ("update", "download"))
             or (not os.path.exists(self.extract_dir))

pooch/tests/test_processors.py

@@ -247,18 +247,41 @@ def _unpacking_expected_paths_and_logs(archive, members, path, name):
     [(Unzip, ".zip"), (Untar, ".tar.gz")],
 )
 def test_unpacking_members_then_no_members(processor_class, extension):
-    """Test that calling with members then without them works.
-
+    """
+    Test that calling with valid members then without them works.
     https://github.com/fatiando/pooch/issues/364
     """
+    with TemporaryDirectory() as local_store:
+        pup = Pooch(path=Path(local_store), base_url=BASEURL, registry=REGISTRY)
+
+        # Do a first fetch with an existing member
+        processor1 = processor_class(members=["store/tiny-data.txt"])
+        filenames1 = pup.fetch("store" + extension, processor=processor1)
+        assert len(filenames1) == 1
+
+        # Do a second fetch with no members
+        processor2 = processor_class()
+        filenames2 = pup.fetch("store" + extension, processor=processor2)
+        assert len(filenames2) > 1
+
 
+@pytest.mark.network
+@pytest.mark.parametrize(
+    "processor_class,extension",
+    [(Unzip, ".zip"), (Untar, ".tar.gz")],
+)
+def test_unpacking_wrong_members_then_no_members(processor_class, extension):
+    """
+    Test that calling with invalid members then without them works.
+    https://github.com/fatiando/pooch/issues/364
+    """
     with TemporaryDirectory() as local_store:
         pup = Pooch(path=Path(local_store), base_url=BASEURL, registry=REGISTRY)
 
         # Do a first fetch with incorrect member
-        processor1 = processor_class(members=["tiny-data.txt"])
+        processor1 = processor_class(members=["not-a-valid-file.csv"])
         filenames1 = pup.fetch("store" + extension, processor=processor1)
-        assert len(filenames1) == 1
+        assert len(filenames1) == 0
 
         # Do a second fetch with no members
         processor2 = processor_class()