az vm image terms: check for missing version in URN

[jrtknauer]

The Command

az vm image terms and its subcommands.

The Issue

az vm image terms and its subcommands can be issued with either individual options to specify the marketplace product (--offer, --plan, etc.) - or instead provide the fully qualified URN using --urn. However, when passing a malformed URN, such as one that is missing the version component, the command hard fails:

# Example URN which works as intended
$ az vm image terms show --urn Canonical:0001-com-ubuntu-pro-jammy:pro-22_04-lts:22.04.202305310

# Example URN which hard fails with a less than obvious error message
$ az vm image terms show --urn Canonical:0001-com-ubuntu-pro-jammy:pro-22_04-lts:
The command failed with an unexpected error. Here is the traceback:
(", AttributeError: 'list' object has no attribute 'get'", 'Unable to deserialize to object: type', AttributeError("'list' object has no attribute 'get'"))
Traceback (most recent call last):
  File "/opt/az/lib/python3.10/site-packages/azure/mgmt/compute/_serialization.py", line 1430, in _deserialize
    found_value = key_extractor(attr, attr_desc, data)
  File "/opt/az/lib/python3.10/site-packages/azure/mgmt/compute/_serialization.py", line 1177, in rest_key_extractor
    return working_data.get(key)
AttributeError: 'list' object has no attribute 'get'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/opt/az/lib/python3.10/site-packages/knack/cli.py", line 233, in invoke
    cmd_result = self.invocation.execute(args)
  File "/opt/az/lib/python3.10/site-packages/azure/cli/core/commands/__init__.py", line 663, in execute
    raise ex
  File "/opt/az/lib/python3.10/site-packages/azure/cli/core/commands/__init__.py", line 726, in _run_jobs_serially
    results.append(self._run_job(expanded_arg, cmd_copy))
  File "/opt/az/lib/python3.10/site-packages/azure/cli/core/commands/__init__.py", line 697, in _run_job
    result = cmd_copy(params)
  File "/opt/az/lib/python3.10/site-packages/azure/cli/core/commands/__init__.py", line 333, in __call__
    return self.handler(*args, **kwargs)
  File "/opt/az/lib/python3.10/site-packages/azure/cli/core/commands/command_operation.py", line 363, in handler
    show_exception_handler(ex)
  File "/opt/az/lib/python3.10/site-packages/azure/cli/core/commands/arm.py", line 429, in show_exception_handler
    raise ex
  File "/opt/az/lib/python3.10/site-packages/azure/cli/core/commands/command_operation.py", line 361, in handler
    return op(**command_args)
  File "/opt/az/lib/python3.10/site-packages/azure/cli/command_modules/vm/custom.py", line 2441, in get_terms
    publisher, offer, plan = _terms_prepare(cmd, urn, publisher, offer, plan)
  File "/opt/az/lib/python3.10/site-packages/azure/cli/command_modules/vm/custom.py", line 2377, in _terms_prepare
    image = show_vm_image(cmd, urn)
  File "/opt/az/lib/python3.10/site-packages/azure/cli/command_modules/vm/custom.py", line 2327, in show_vm_image
    return client.virtual_machine_images.get(location, publisher, offer, sku, version)
  File "/opt/az/lib/python3.10/site-packages/azure/core/tracing/decorator.py", line 78, in wrapper_use_tracer
    return func(*args, **kwargs)
  File "/opt/az/lib/python3.10/site-packages/azure/mgmt/compute/v2022_11_01/operations/_virtual_machine_images_operations.py", line 320, in get
    deserialized = self._deserialize("VirtualMachineImage", pipeline_response)
  File "/opt/az/lib/python3.10/site-packages/azure/mgmt/compute/_serialization.py", line 1375, in __call__
    return self._deserialize(target_obj, data)
  File "/opt/az/lib/python3.10/site-packages/azure/mgmt/compute/_serialization.py", line 1445, in _deserialize
    raise_with_traceback(DeserializationError, msg, err)
  File "/opt/az/lib/python3.10/site-packages/azure/core/exceptions.py", line 78, in raise_with_traceback
    raise error.with_traceback(exc_traceback)
  File "/opt/az/lib/python3.10/site-packages/azure/mgmt/compute/_serialization.py", line 1430, in _deserialize
    found_value = key_extractor(attr, attr_desc, data)
  File "/opt/az/lib/python3.10/site-packages/azure/mgmt/compute/_serialization.py", line 1177, in rest_key_extractor
    return working_data.get(key)
azure.core.exceptions.DeserializationError: (", AttributeError: 'list' object has no attribute 'get'", 'Unable to deserialize to object: type', AttributeError("'list' object has no attribute 'get'"))
To check existing issues, please visit: https://github.com/Azure/azure-cli/issues

This issue is not to be confused with an URN with an invalid version. The command also correctly handles some incomplete URNs:

# A better error message
$ az vm image terms show --urn Canonical:0001-com-ubuntu-pro-jammy:
usage error: urn should be in the format of publisher:offer:sku:version.

# Not as good as the previous error, but much better than the one which is being reported
$ az vm image terms show --urn Canonical:0001-com-ubuntu-pro-jammy::
(BadRequest) The request URL is not valid.
Code: BadRequest
Message: The request URL is not valid.
Inner error: {
    "internalErrorCode": "RequestUrlInvalid"
}

The Solution

Azure Marketplace URNs are well defined, and Azure CLI should report that the URN is incomplete:

# An error message that tells the user what the URN is missing
$ az vm image terms show --urn Canonical:0001-com-ubuntu-pro-jammy:pro-22_04-lts:
usage error: urn is missing "version" in the publisher:offer:sku:version format

Other Considerations

This is a low impact enhancement. Users should be smart enough to input a valid URN (once again, the documentation is very clear on what an URN is comprised of), but I can attest to this error message being an issue for those who are less-than-familiar with Azure.

[yonzhan]

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