Override sync strategy

Author: Rakshil Modi

awscli/customizations/s3/subcommands.py

@@ -40,6 +40,7 @@
     NeverSync,
     SizeAndLastModifiedSync,
 )
+from awscli.customizations.s3.syncstrategy.nooverwrite import NoOverwriteSync
 from awscli.customizations.s3.utils import (
     AppendFilter,
     RequestParamsMapper,
@@ -1296,10 +1297,15 @@ def choose_sync_strategies(self):
         of its self when the event is emitted.
         """
         sync_strategies = {}
-        # Set the default strategies.
-        sync_strategies['file_at_src_and_dest_sync_strategy'] = (
-            SizeAndLastModifiedSync()
-        )
+        if self.parameters.get('no_overwrite'):
+            sync_strategies['file_at_src_and_dest_sync_strategy'] = (
+                NoOverwriteSync()
+            )
+        else:
+            # Set the default strategies.
+            sync_strategies['file_at_src_and_dest_sync_strategy'] = (
+                SizeAndLastModifiedSync()
+            )
         sync_strategies['file_not_at_dest_sync_strategy'] = MissingFileSync()
         sync_strategies['file_not_at_src_sync_strategy'] = NeverSync()
 
@@ -1841,11 +1847,6 @@ def _validate_no_overwrite_for_download_streaming(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

@@ -12,34 +12,20 @@
 # 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 will only sync files that don't exist at the destination.
-    If a file exists at both source and destination, it will be skipped regardless
-    of size or modification time differences.
+    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 __init__(self, sync_type='file_not_at_dest'):
-        super().__init__(sync_type)
-
     def determine_should_sync(self, src_file, dest_file):
-        if self.sync_type == 'file_not_at_dest':
-            LOG.debug(
-                f"syncing: {src_file.src} -> {src_file.dest}, file does not exist at destination"
-            )
-            return True
-        elif self.sync_type == 'file_at_src_and_dest':
-            # Files exist at both locations must not be synced
-            LOG.debug(
-                f"warning: skipping {src_file.src} -> {src_file.dest}, file exists at destination"
-            )
-            return False
+        LOG.debug(
+            f"warning: skipping {src_file.src} -> {src_file.dest}, file exists at destination"
+        )
         return False

awscli/customizations/s3/syncstrategy/register.py

@@ -50,7 +50,6 @@ def register_sync_strategies(command_table, session, **kwargs):
     register_sync_strategy(session, DeleteSync, 'file_not_at_src')
 
     # Register the noOverwrite sync strategy
-    register_sync_strategy(session, NoOverwriteSync, 'file_not_at_dest')
     register_sync_strategy(session, NoOverwriteSync, 'file_at_src_and_dest')
 
     # Register additional sync strategies here...

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

@@ -20,56 +20,10 @@
 
 @pytest.fixture
 def sync_strategy():
-    return NoOverwriteSync()
+    return NoOverwriteSync('file_at_src_and_dest')
 
 
-def test_file_does_not_exist_at_destination(sync_strategy):
-    time_src = datetime.datetime.now()
-
-    src_file = FileStat(
-        src='',
-        dest='',
-        compare_key='test.py',
-        size=10,
-        last_update=time_src,
-        src_type='s3',
-        dest_type='local',
-        operation_name='download',
-    )
-    dest_file = None
-    should_sync = sync_strategy.determine_should_sync(src_file, dest_file)
-    assert should_sync
-
-
-def test_file_exists_at_destination_with_different_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='s3',
-        dest_type='s3',
-        operation_name='copy',
-    )
-    dest_file = FileStat(
-        src='',
-        dest='',
-        compare_key='test1.py',
-        size=100,
-        last_update=time_src,
-        src_type='s3',
-        dest_type='s3',
-        operation_name='',
-    )
-    should_sync = sync_strategy.determine_should_sync(src_file, dest_file)
-    assert should_sync
-
-
-def test_file_exists_at_destination_with_same_key():
-    sync_strategy = 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(