Fix cp/mv -I dropping all stdin paths after the first two

gslib/commands/cp.py

@@ -1043,8 +1043,15 @@ def _ConstructNameExpansionIteratorDstTupleIterator(self, src_url_strs_iter,
       self.has_file_dst = self.has_file_dst or exp_dst_url.IsFileUrl()
       self.has_cloud_dst = self.has_cloud_dst or exp_dst_url.IsCloudUrl()
       self.provider_types.add(exp_dst_url.scheme)
-      self.combined_src_urls = list(itertools.chain(self.combined_src_urls,
-                                               src_url_str))
+      # combined_src_urls is only consumed by SeekAheadNameExpansionIterator,
+      # which is not used when reading sources from stdin (-I). Do not touch
+      # src_url_str in that case: it is a one-shot stdin iterator that is
+      # already being consumed by the NameExpansionIterator above, and
+      # materializing it here would silently drop every path that has not
+      # yet been read by the copy loop.
+      if not copy_helper_opts.read_args_from_stdin:
+        self.combined_src_urls = list(
+            itertools.chain(self.combined_src_urls, src_url_str))
 
       yield name_expansion_iterator_dst_tuple
 

gslib/tests/test_cp.py

@@ -24,6 +24,7 @@
 import binascii
 import datetime
 import gzip
+import io
 import logging
 import os
 import pickle
@@ -5117,6 +5118,32 @@ def test_storage_class_on_local_destination_fails(self):
           suri(bucket_uri, 'object'), 'local_file'
       ])
 
+  def test_read_args_from_stdin_copies_all_paths(self):
+    """Tests that cp -I copies every path from stdin, not just the first two.
+
+    Regression test for a bug where the stdin iterator was materialized into a
+    list while the name expansion iterator (which had already buffered two
+    entries for its plurality check) still held a reference to it, causing
+    all paths after the second one to be silently dropped.
+    """
+    src_dir = self.CreateTempDir()
+    dst_dir = self.CreateTempDir()
+    num_files = 5
+    fpaths = [
+        self.CreateTempFile(tmpdir=src_dir,
+                            file_name='f%d' % i,
+                            contents=('data%d' % i).encode('ascii'))
+        for i in range(num_files)
+    ]
+    stdin_lines = '\n'.join(fpaths) + '\n'
+    with mock.patch('sys.stdin', io.StringIO(stdin_lines)):
+      self.RunCommand('cp', ['-I', dst_dir])
+    copied = sorted(os.listdir(dst_dir))
+    self.assertEqual(copied, ['f%d' % i for i in range(num_files)])
+    for i in range(num_files):
+      with open(os.path.join(dst_dir, 'f%d' % i), 'rb') as f:
+        self.assertEqual(f.read(), ('data%d' % i).encode('ascii'))
+
   def test_read_args_from_stdin_with_source_urls_fails(self):
     bucket_uri = self.CreateBucket()
     with self.assertRaisesRegex(