[ML] Deployment templates bug fixes (#9666)

* dt bug fix

* refactoring

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

---------

Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>

Author: PratibhaShrivastav18

src/machinelearningservices/CHANGELOG.rst

@@ -1,3 +1,12 @@
+## Unreleased
+
+### Azure Machine Learning CLI (v2) v 2.43.0
+
+- `az ml deployment-template update`
+  - Fix KeyError crash when updating a deployment template that has no tags or description.
+- `az ml deployment-template list`
+  - Fix table output (`-o table`) not rendering any data rows.
+
 ## 2026-02-24
 
 ### Azure Machine Learning CLI (v2) v 2.42.0

src/machinelearningservices/azext_mlv2/manual/_format.py

@@ -313,6 +313,28 @@ def transform_deployment_list(result):
     return transformed
 
 
+def transform_deployment_template_list(result):
+    """Table transformer for 'az ml deployment-template list'."""
+    transformed = []
+    for r in result:
+        # Fields may be at top level or nested under "properties"
+        props = r.get("properties", r)
+        entry = OrderedDict(
+            [
+                ("name", props.get("name")),
+                ("version", props.get("version")),
+                ("stage", props.get("stage")),
+                ("deploymentTemplateType", props.get("deploymentTemplateType")),
+                ("defaultInstanceType", props.get("defaultInstanceType")),
+                ("instanceCount", props.get("instanceCount")),
+                ("description", props.get("description")),
+            ]
+        )
+        transformed.append(entry)
+
+    return transformed
+
+
 def transform_endpoint_list(result):
     transformed = []
     for r in result:

src/machinelearningservices/azext_mlv2/manual/commands.py

@@ -21,6 +21,7 @@
     transform_data,
     transform_datastore,
     transform_deployment_list,
+    transform_deployment_template_list,
     transform_endpoint_list,
     transform_environment,
     transform_environment_list,
@@ -229,7 +230,8 @@ def load_command_table(self, _):
     with self.command_group("ml deployment-template", client_factory=cf_ml_cl, is_preview=True) as g:
         custom_tmpl = "azext_mlv2.manual.custom.deployment_template#{}"
         custom_deployment_template = CliCommandType(operations_tmpl=custom_tmpl)
-        g.custom_command("list", "ml_deployment_template_list", command_type=custom_deployment_template)
+        g.custom_command("list", "ml_deployment_template_list", command_type=custom_deployment_template,
+                         table_transformer=transform_deployment_template_list)
         g.custom_show_command("show", "ml_deployment_template_show")
         g.custom_command("create", "ml_deployment_template_create", supports_no_wait=True,
                          command_type=custom_deployment_template)

src/machinelearningservices/azext_mlv2/manual/custom/deployment_template.py

@@ -146,8 +146,11 @@ def _ml_deployment_template_update(
     try:
         deployment_template = ml_client.deployment_templates.get(name=parameters["name"], version=parameters["version"])
 
-        deployment_template.description = parameters["description"]
-        deployment_template.tags = parameters["tags"]
+        # Only update optional fields if they are explicitly present in parameters
+        if "description" in parameters:
+            deployment_template.description = parameters.get("description")
+        if "tags" in parameters:
+            deployment_template.tags = parameters.get("tags")
 
         deployment_template_result = ml_client.deployment_templates.create_or_update(deployment_template)