Adding new Sync strategy

Updated test case

Updated doc comment

Added test cases

Updating Sync Strategy

Updated comments

Updated comments

Override sync strategy

Overridding sync strategy

Author: Rakshil Modi

awscli/customizations/s3/subcommands.py

@@ -1314,7 +1314,6 @@ def choose_sync_strategies(self):
                     sync_type = override_sync_strategy.sync_type
                     sync_type += '_sync_strategy'
                     sync_strategies[sync_type] = override_sync_strategy
-
         return sync_strategies
 
     def run(self):
@@ -1830,11 +1829,6 @@ def _validate_streaming_no_overwrite_for_download_parameter(self):
         """
         Validates that no-overwrite parameter is not used with streaming downloads.
 
-        When downloading from S3 to stdout (streaming download), the no-overwrite
-        parameter doesn't make sense since stdout is not a file that can be checked
-        for existence. This method checks for this invalid combination and raises
-        an appropriate error.
-
         Raises:
             ParamValidationError: If no-overwrite is specified with a streaming download.
         """

awscli/customizations/s3/syncstrategy/nooverwrite.py

@@ -0,0 +1,34 @@
+# Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"). You
+# may not use this file except in compliance with the License. A copy of
+# the License is located at
+#
+# http://aws.amazon.com/apache2.0/
+#
+# or in the "license" file accompanying this file. This file is
+# distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
+# ANY KIND, either express or implied. See the License for the specific
+# language governing permissions and limitations under the License.
+import logging
+
+from awscli.customizations.s3.subcommands import NO_OVERWRITE
+from awscli.customizations.s3.syncstrategy.base import BaseSync
+
+LOG = logging.getLogger(__name__)
+
+
+class NoOverwriteSync(BaseSync):
+    """Sync strategy that prevents overwriting of existing files at the destination.
+    This strategy is used only for files that exist at both source and destination
+    (file_at_src_and_dest_sync_strategy). It always returns False to prevent any
+    overwriting of existing files, regardless of size or modification time differences.
+    """
+
+    ARGUMENT = NO_OVERWRITE
+
+    def determine_should_sync(self, src_file, dest_file):
+        LOG.debug(
+            f"warning: skipping {src_file.src} -> {src_file.dest}, file exists at destination"
+        )
+        return False

awscli/customizations/s3/syncstrategy/register.py

@@ -14,6 +14,7 @@
 from awscli.customizations.s3.syncstrategy.exacttimestamps import (
     ExactTimestampsSync,
 )
+from awscli.customizations.s3.syncstrategy.nooverwrite import NoOverwriteSync
 from awscli.customizations.s3.syncstrategy.sizeonly import SizeOnlySync
 
 
@@ -48,4 +49,7 @@ def register_sync_strategies(command_table, session, **kwargs):
     # Register the delete sync strategy.
     register_sync_strategy(session, DeleteSync, 'file_not_at_src')
 
+    # Register the noOverwrite sync strategy
+    register_sync_strategy(session, NoOverwriteSync, 'file_at_src_and_dest')
+
     # Register additional sync strategies here...

tests/unit/customizations/s3/syncstrategy/test_nooverwrite.py

@@ -0,0 +1,50 @@
+# Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+#
+# Licensed under the Apache License, Version 2.0 (the "License"). You
+# may not use this file except in compliance with the License. A copy of
+# the License is located at
+#
+# http://aws.amazon.com/apache2.0/
+#
+# or in the "license" file accompanying this file. This file is
+# distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF
+# ANY KIND, either express or implied. See the License for the specific
+# language governing permissions and limitations under the License.
+import datetime
+
+import pytest
+
+from awscli.customizations.s3.filegenerator import FileStat
+from awscli.customizations.s3.syncstrategy.nooverwrite import NoOverwriteSync
+
+
+@pytest.fixture
+def sync_strategy():
+    return NoOverwriteSync('file_at_src_and_dest')
+
+
+def test_file_exists_at_destination_with_same_key(sync_strategy):
+    time_src = datetime.datetime.now()
+
+    src_file = FileStat(
+        src='',
+        dest='',
+        compare_key='test.py',
+        size=10,
+        last_update=time_src,
+        src_type='local',
+        dest_type='s3',
+        operation_name='upload',
+    )
+    dest_file = FileStat(
+        src='',
+        dest='',
+        compare_key='test.py',
+        size=100,
+        last_update=time_src,
+        src_type='local',
+        dest_type='s3',
+        operation_name='',
+    )
+    should_sync = sync_strategy.determine_should_sync(src_file, dest_file)
+    assert not should_sync