`az storage blob upload` does not allow for uploading empty blob with `--data`

[cecheta]

Describe the bug

The command az storage blob upload should allow you to upload an empty file to blob storage, using --data ''. However, it gives this error:

usage error: please specify one of --file and --data to upload.

Related command

az storage blob upload

Errors

usage error: please specify one of --file and --data to upload.

Issue script & Debug output

~ az storage blob upload --account-name myaccount --container-name mycontainer --name file.txt --data '' --debug
cli.knack.cli: Command arguments: ['storage', 'blob', 'upload', '--account-name', 'myaccount', '--container-name', 'mycontainer', '--name', 'file.txt', '--data', '', '--debug']
cli.knack.cli: __init__ debug log:
Enable color in terminal.
cli.knack.cli: Event: Cli.PreExecute []
cli.knack.cli: Event: CommandParser.OnGlobalArgumentsCreate [<function CLILogging.on_global_arguments at 0x7f2b6822ca40>, <function OutputProducer.on_global_arguments at 0x7f2b67f8cb80>, <function CLIQuery.on_global_arguments at 0x7f2b67fbe0c0>]
cli.knack.cli: Event: CommandInvoker.OnPreCommandTableCreate []
cli.azure.cli.core: Modules found from index for 'storage': ['azure.cli.command_modules.storage']
cli.azure.cli.core: Loading command modules:
cli.azure.cli.core: Name                  Load Time    Groups  Commands
cli.azure.cli.core: storage                   0.151        60       275
cli.azure.cli.core: Total (1)                 0.151        60       275
cli.azure.cli.core: These extensions are not installed and will be skipped: ['azext_ai_examples', 'azext_next']
cli.azure.cli.core: Loading extensions:
cli.azure.cli.core: Name                  Load Time    Groups  Commands  Directory
cli.azure.cli.core: Total (0)                 0.000         0         0
cli.azure.cli.core: Loaded 60 groups, 275 commands.
cli.azure.cli.core: Found a match in the command table.
cli.azure.cli.core: Raw command  : storage blob upload
cli.azure.cli.core: Command table: storage blob upload
cli.knack.cli: Event: CommandInvoker.OnPreCommandTableTruncate [<function AzCliLogging.init_command_file_logging at 0x7f2b66d684a0>]
cli.azure.cli.core.azlogging: metadata file logging enabled - writing logs to '/home/cecheta/.azure/commands/2025-07-21.17-01-46.storage_blob_upload.119686.log'.
az_command_data_logger: command args: storage blob upload --account-name {} --container-name {} --name {} --data {} --debug
cli.knack.cli: Event: CommandInvoker.OnPreArgumentLoad [<function register_global_subscription_argument.<locals>.add_subscription_parameter at 0x7f2b66db3b00>]
cli.knack.cli: Event: CommandInvoker.OnPostArgumentLoad []
cli.knack.cli: Event: CommandInvoker.OnPostCommandTableCreate [<function register_ids_argument.<locals>.add_ids_arguments at 0x7f2b66db3ba0>, <function register_cache_arguments.<locals>.add_cache_arguments at 0x7f2b66db3ce0>, <function register_upcoming_breaking_change_info.<locals>.update_breaking_change_info at 0x7f2b66db3d80>]
cli.knack.cli: Event: CommandInvoker.OnCommandTableLoaded []
cli.knack.cli: Event: CommandInvoker.OnPreParseArgs []
cli.knack.cli: Event: CommandInvoker.OnPostParseArgs [<function OutputProducer.handle_output_argument at 0x7f2b67f8cc20>, <function CLIQuery.handle_query_parameter at 0x7f2b67fbe160>, <function register_ids_argument.<locals>.parse_ids_arguments at 0x7f2b66db3c40>]
Argument '--data' is in preview and under development. Reference and support levels: https://aka.ms/CLI_refstatus
cli.azure.cli.command_modules.storage._validators: Try to get storage auth_mode value from environment variables or config file.
cli.azure.cli.command_modules.storage._validators: Try to get storage connection_string value from environment variables or config file.
cli.azure.cli.command_modules.storage._validators: Try to get storage key value from environment variables or config file.
cli.azure.cli.command_modules.storage._validators: Try to get storage sas_token value from environment variables or config file.
cli.azure.cli.core.azclierror: Traceback (most recent call last):
  File "/home/linuxbrew/.linuxbrew/Cellar/azure-cli/2.75.0/libexec/lib/python3.12/site-packages/knack/cli.py", line 233, in invoke
    cmd_result = self.invocation.execute(args)
                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/home/linuxbrew/.linuxbrew/Cellar/azure-cli/2.75.0/libexec/lib/python3.12/site-packages/azure/cli/core/commands/__init__.py", line 654, in execute
    self._validation(expanded_arg)
  File "/home/linuxbrew/.linuxbrew/Cellar/azure-cli/2.75.0/libexec/lib/python3.12/site-packages/knack/invocation.py", line 113, in _validation
    self._validate_arg_level(parsed_ns)
  File "/home/linuxbrew/.linuxbrew/Cellar/azure-cli/2.75.0/libexec/lib/python3.12/site-packages/azure/cli/core/commands/__init__.py", line 925, in _validate_arg_level
    validator(**self._build_kwargs(validator, ns))
  File "/home/linuxbrew/.linuxbrew/Cellar/azure-cli/2.75.0/libexec/lib/python3.12/site-packages/azure/cli/command_modules/storage/_validators.py", line 2315, in validate_upload_blob
    raise InvalidArgumentValueError("usage error: please specify one of --file and --data to upload.")
azure.cli.core.azclierror.InvalidArgumentValueError: usage error: please specify one of --file and --data to upload.

cli.azure.cli.core.azclierror: usage error: please specify one of --file and --data to upload.
az_command_data_logger: usage error: please specify one of --file and --data to upload.
cli.knack.cli: Event: Cli.PostExecute [<function AzCliLogging.deinit_cmd_metadata_logging at 0x7f2b66d68720>]
az_command_data_logger: exit code: 1
cli.__main__: Command ran in 0.573 seconds (init: 0.135, invoke: 0.438)
telemetry.main: Begin splitting cli events and extra events, total events: 1
telemetry.client: Accumulated 0 events. Flush the clients.
telemetry.main: Finish splitting cli events and extra events, cli events: 1
telemetry.save: Save telemetry record of length 3986 in cache file under /home/cecheta/.azure/telemetry/20250721170147247
telemetry.main: Begin creating telemetry upload process.
telemetry.process: Creating upload process: "/home/linuxbrew/.linuxbrew/Cellar/azure-cli/2.75.0/libexec/bin/python /home/linuxbrew/.linuxbrew/Cellar/azure-cli/2.75.0/libexec/lib/python3.12/site-packages/azure/cli/telemetry/__init__.py /home/cecheta/.azure /home/cecheta/.azure/telemetry/20250721170147247"
telemetry.process: Return from creating process 119705
telemetry.main: Finish creating telemetry upload process.

Expected behavior

An empty blob should be uploaded to Blob storage.

Environment Summary

azure-cli 2.75.0

core 2.75.0
telemetry 1.1.0

Extensions:
application-insights 1.2.3
devcenter 7.0.0
ml 2.38.0
ssh 2.0.6

Dependencies:
msal 1.33.0b1
azure-mgmt-resource 23.3.0

Python location '/home/linuxbrew/.linuxbrew/Cellar/azure-cli/2.75.0/libexec/bin/python'
Config directory '/home/cecheta/.azure'
Extensions directory '/home/cecheta/.azure/cliextensions'

Python (Linux) 3.12.11 (main, Jun 3 2025, 15:41:47) [GCC 11.4.0]

Legal docs and information: aka.ms/AzureCliLegal

Your CLI is up-to-date.

Additional context

Presumably, the error comes from here, where the value is checked for "falsy" rather than explicitly None.

[yonzhan]

Thank you for opening this issue, we will look into it.