Raise clear error when s3 config block is a plain string

awscli/customizations/s3/subcommands.py

@@ -459,7 +459,7 @@
 }
 
 CHECKSUM_ALGORITHM = {
-        'name': 'checksum-algorithm', 'choices': ['CRC64NVME', 'CRC32', 'SHA256', 'SHA1', 'CRC32C', 'SHA512', 'XXHASH64', 'XXHASH3', 'XXHASH128'],
+        'name': 'checksum-algorithm', 'choices': ['CRC64NVME', 'CRC32', 'SHA256', 'SHA1', 'CRC32C', 'SHA512', 'XXHASH64', 'XXHASH3', 'XXHASH128', 'MD5'],
         'help_text': 'Indicates the algorithm used to create the checksum for the object.'
 }
 
@@ -795,6 +795,15 @@ def _run_main(self, parsed_args, parsed_globals):
 
 class S3TransferCommand(S3Command):
     def _run_main(self, parsed_args, parsed_globals):
+        s3_config = self._session.get_scoped_config().get('s3', {})
+        if not isinstance(s3_config, dict):
+            raise transferconfig.InvalidConfigError(
+                "Invalid value for 's3' in your AWS config file. "
+                "The s3 section must use indented sub-keys, not a plain "
+                "string value. For example:\n\n"
+                "s3 =\n"
+                "  max_concurrent_requests = 10\n"
+            )
         super(S3TransferCommand, self)._run_main(parsed_args, parsed_globals)
         self._convert_path_args(parsed_args)
         params = self._build_call_parameters(parsed_args, {})
@@ -810,7 +819,7 @@ def _run_main(self, parsed_args, parsed_globals):
         cmd_params.add_v2_debug(parsed_globals)
 
         runtime_config = transferconfig.RuntimeConfig().build_config(
-            **self._session.get_scoped_config().get('s3', {}))
+            **s3_config)
         cmd = CommandArchitecture(self._session, self.NAME,
                                   cmd_params.parameters,
                                   runtime_config)

tests/unit/customizations/s3/test_subcommands.py

@@ -19,7 +19,7 @@
 from awscli.customizations.s3.subcommands import CommandParameters, \
     CommandArchitecture, CpCommand, SyncCommand, ListCommand, \
     RbCommand, get_client
-from awscli.customizations.s3.transferconfig import RuntimeConfig
+from awscli.customizations.s3.transferconfig import RuntimeConfig, InvalidConfigError
 from awscli.customizations.s3.syncstrategy.base import \
     SizeAndLastModifiedSync, NeverSync, MissingFileSync
 from awscli.testutils import mock, unittest, BaseAWSHelpOutputTest, \
@@ -80,6 +80,20 @@ def test_rb_command_with_force_requires_strict_path(self):
                                       parsed_globals=self.parsed_globals)
 
 
+class TestS3ConfigValidation(unittest.TestCase):
+    def setUp(self):
+        self.session = mock.Mock()
+        self.parsed_args = mock.Mock()
+        self.parsed_globals = mock.Mock()
+
+    def test_plain_string_s3_config_raises_invalid_config_error(self):
+        self.session.get_scoped_config.return_value = {'s3': ''}
+        cp_command = CpCommand(self.session)
+        with self.assertRaises(InvalidConfigError) as ctx:
+            cp_command._run_main(self.parsed_args, self.parsed_globals)
+        self.assertIn('nested section', str(ctx.exception))
+
+
 class TestLSCommand(unittest.TestCase):
     def setUp(self):
         self.session = mock.Mock()
@@ -753,6 +767,14 @@ def test_validate_checksum_algorithm_download_error(self):
             cmd_params.add_paths(paths)
             self.assertIn('Expected checksum-algorithm parameter to be used with one of following path formats', cm.msg)
 
+    def test_validate_checksum_algorithm_md5_upload(self):
+        paths = [self.file_creator.rootdir, 's3://bucket/key']
+        parameters = {'checksum_algorithm': 'MD5'}
+        cmd_params = CommandParameters('cp', parameters, '')
+        cmd_params.add_paths(paths)
+        self.assertEqual(cmd_params.parameters['checksum_algorithm'], 'MD5')
+
+
     def test_validate_checksum_algorithm_sync_download_error(self):
         paths = ['s3://bucket/key', self.file_creator.rootdir]
         parameters = {'checksum_algorithm': 'CRC32C'}