omit empty tags in RunnerDeployment (#16075)

src/prefect/deployments/runner.py

@@ -77,6 +77,7 @@ def fast_flow():
     PREFECT_DEFAULT_WORK_POOL_NAME,
     PREFECT_UI_URL,
 )
+from prefect.types import ListOfNonEmptyStrings
 from prefect.types.entrypoint import EntrypointType
 from prefect.utilities.asyncutils import sync_compatible
 from prefect.utilities.callables import ParameterSchema, parameter_schema
@@ -140,7 +141,7 @@ class RunnerDeployment(BaseModel):
     version: Optional[str] = Field(
         default=None, description="An optional version for the deployment."
     )
-    tags: List[str] = Field(
+    tags: ListOfNonEmptyStrings = Field(
         default_factory=list,
         description="One of more tags to apply to this deployment.",
     )

src/prefect/types/__init__.py

@@ -82,24 +82,30 @@ def check_variable_value(value: object) -> object:
     return value
 
 
-def cast_none_to_empty_dict(value: Any) -> dict[str, Any]:
-    if value is None:
-        return {}
-    return value
-
-
 StrictVariableValue = Annotated[VariableValue, BeforeValidator(check_variable_value)]
 
 LaxUrl = Annotated[str, BeforeValidator(lambda x: str(x).strip())]
 
 StatusCode = Annotated[int, Field(ge=100, le=599)]
 
+
+def cast_none_to_empty_dict(value: Any) -> dict[str, Any]:
+    if value is None:
+        return {}
+    return value
+
+
 KeyValueLabels = Annotated[
     dict[str, Union[StrictBool, StrictInt, StrictFloat, str]],
     BeforeValidator(cast_none_to_empty_dict),
 ]
 
 
+ListOfNonEmptyStrings = Annotated[
+    List[str], BeforeValidator(lambda x: [s for s in x if s.strip()])
+]
+
+
 class SecretDict(pydantic.Secret[Dict[str, Any]]):
     pass
 
@@ -147,6 +153,7 @@ def validate_set_T_from_delim_string(
     "LogLevel",
     "NonNegativeInteger",
     "PositiveInteger",
+    "ListOfNonEmptyStrings",
     "NonNegativeFloat",
     "Name",
     "NameOrEmpty",