Improve the documentation of resolve_filespecs. Also have it return 0…

… for num_shards instead of None when there are no shards; update all call sites to reflect this change.

PiperOrigin-RevId: 213698824

nucleus/util/io_utils.py

@@ -52,9 +52,9 @@ def ParseShardedFileSpec(spec):  # pylint:disable=invalid-name
       'gs://some/file@200.txt'. Here, '@200' specifies the number of shards.
 
   Returns:
-    basename: The basename for the files.
-    num_shards: The number of shards.
-    suffix: The suffix if there is one, or '' if not.
+    basename: str. The basename for the files.
+    num_shards: int >= 0. The number of shards.
+    suffix: str. The suffix if there is one, or '' if not.
   Raises:
     ShardError: If the spec is not a valid sharded specification.
   """
@@ -188,8 +188,9 @@ def resolve_filespecs(shard, *filespecs):
       shard-specific file paths.
 
   Returns:
-    A list. The first element is the number of shards, followed by the
-    shard-specific paths for each filespec, in order.
+    A list. The first element is the number of shards, which is an int >= 1 when
+    filespecs contains sharded paths and 0 if none do. All subsequent
+    returned values follow the shard-specific paths for each filespec, in order.
 
   Raises:
     ValueError: if any filespecs are inconsistent.
@@ -200,7 +201,7 @@ def resolve_filespecs(shard, *filespecs):
   master = filespecs[0]
   master_is_sharded = IsShardedFileSpec(master)
 
-  master_num_shards = None
+  master_num_shards = 0
   if master_is_sharded:
     _, master_num_shards, _ = ParseShardedFileSpec(master)
     if shard >= master_num_shards or shard < 0:

nucleus/util/io_utils_test.py

@@ -34,27 +34,63 @@ class IOTest(parameterized.TestCase):
 
   @parameterized.parameters(
       # Unsharded outputs pass through as expected.
-      (0, ['foo.txt'], [None, 'foo.txt']),
-      (0, ['foo.txt', 'bar.txt'], [None, 'foo.txt', 'bar.txt']),
-      (0, ['bar.txt', 'foo.txt'], [None, 'bar.txt', 'foo.txt']),
+      dict(task_id=0, filespecs=['foo.txt'], expected=[0, 'foo.txt']),
+      dict(
+          task_id=0,
+          filespecs=['foo.txt', 'bar.txt'],
+          expected=[0, 'foo.txt', 'bar.txt']),
+      dict(
+          task_id=0,
+          filespecs=['bar.txt', 'foo.txt'],
+          expected=[0, 'bar.txt', 'foo.txt']),
       # It's ok to have False values for other bindings.
-      (0, ['foo.txt', None], [None, 'foo.txt', None]),
-      (0, ['foo.txt', ''], [None, 'foo.txt', '']),
-      (0, ['foo@10.txt', None], [10, 'foo-00000-of-00010.txt', None]),
-      (0, ['foo@10.txt', ''], [10, 'foo-00000-of-00010.txt', '']),
+      dict(
+          task_id=0, filespecs=['foo.txt', None], expected=[0, 'foo.txt',
+                                                            None]),
+      dict(task_id=0, filespecs=['foo.txt', ''], expected=[0, 'foo.txt', '']),
+      dict(
+          task_id=0,
+          filespecs=['foo@10.txt', None],
+          expected=[10, 'foo-00000-of-00010.txt', None]),
+      dict(
+          task_id=0,
+          filespecs=['foo@10.txt', ''],
+          expected=[10, 'foo-00000-of-00010.txt', '']),
       # Simple check that master behaves as expected.
-      (0, ['foo@10.txt', None], [10, 'foo-00000-of-00010.txt', None]),
-      (0, ['foo@10', None], [10, 'foo-00000-of-00010', None]),
-      (1, ['foo@10', None], [10, 'foo-00001-of-00010', None]),
-      (9, ['foo@10', None], [10, 'foo-00009-of-00010', None]),
-      # Make sure we handle sharding of multiple outputs.
-      (0, ['foo@10', 'bar@10', 'baz@10'],
-       [10, 'foo-00000-of-00010', 'bar-00000-of-00010', 'baz-00000-of-00010']),
-      (9, ['foo@10', 'bar@10', 'baz@10'],
-       [10, 'foo-00009-of-00010', 'bar-00009-of-00010', 'baz-00009-of-00010']),
+      dict(
+          task_id=0,
+          filespecs=['foo@10.txt', None],
+          expected=[10, 'foo-00000-of-00010.txt', None]),
+      dict(
+          task_id=0,
+          filespecs=['foo@10', None],
+          expected=[10, 'foo-00000-of-00010', None]),
+      dict(
+          task_id=1,
+          filespecs=['foo@10', None],
+          expected=[10, 'foo-00001-of-00010', None]),
+      dict(
+          task_id=9,
+          filespecs=['foo@10', None],
+          expected=[10, 'foo-00009-of-00010', None]),
+      # Make sure we handle sharding of multiple filespecs.
+      dict(
+          task_id=0,
+          filespecs=['foo@10', 'bar@10', 'baz@10'],
+          expected=[
+              10, 'foo-00000-of-00010', 'bar-00000-of-00010',
+              'baz-00000-of-00010'
+          ]),
+      dict(
+          task_id=9,
+          filespecs=['foo@10', 'bar@10', 'baz@10'],
+          expected=[
+              10, 'foo-00009-of-00010', 'bar-00009-of-00010',
+              'baz-00009-of-00010'
+          ]),
   )
-  def test_resolve_filespecs(self, task_id, outputs, expected):
-    self.assertEqual(io.resolve_filespecs(task_id, *outputs), expected)
+  def test_resolve_filespecs(self, task_id, filespecs, expected):
+    self.assertEqual(io.resolve_filespecs(task_id, *filespecs), expected)
 
   @parameterized.parameters(
       # shard >= num_shards.