Support asset-backed defaults on uri_file/uri_folder/mltable component inputs

[Copilot]

The component schema accepts a default on asset ports (InputPortSchema.default = fields.Str()), but load_component() rejected it with Default value of Input cannot be set: Non-primitive type Input has no default value., because Input._update_default() rejected every non-None default on a non-primitive type.

inputs:
  spaceship_data:
    type: uri_file
    mode: ro_mount
    default: azureml:dsp_da_test_use_case_spaceships_uri_file:50322a7173b6976c

Changes

• constants/_component.py — added IOConstants.ASSET_TYPES_SUPPORTING_DEFAULT (uri_folder, uri_file, mltable) and added "default" to those entries in INPUT_TYPE_COMBINATION so parameter-combination validation permits it. mlflow_model/custom_model are intentionally left out.
• entities/_inputs_outputs/input.py — new _supports_asset_default property; _update_default() now stores a string asset/path reference as-is for the supported types. Non-string defaults (123, True, a nested Input) raise UserErrorException with a message keeping the established Default value of Input '<name>' cannot be set prefix, which the dsl group tests assert on. Unsupported non-primitive types keep the original error. Docstring and the generic __init__ overload updated.
• No serialization changes needed — default is already in Input._IO_KEYS, so _to_dict, _to_rest_object, _from_rest_object and InputPortSchema preserve the reference, type, mode and optional semantics through YAML and REST round trips.
• Invocation semantics fall out of the existing checks — the required-input validation in BaseNode._validate_inputs / PipelineJob already skips inputs where meta.default is not None, so an omitted input is no longer an error and the service applies the default; an explicit value still overrides it without mutating the component definition.
• Tests/fixtures — tests/component/unittests/test_input_defaults.py plus input_asset_defaults_component.yml, input_asset_defaults_pipeline_component.yml, and invalid/input_asset_defaults_invalid_component.yml, covering direct construction, YAML dump/reload, REST round trip, the customer repro for command and pipeline components, override/no-mutation, invalid defaults, and primitive-default regressions.
• CHANGELOG entry under 1.35.0.

component = load_component("pipeline_component.yaml")
component.inputs["spaceship_data"].default
# 'azureml:dsp_da_test_use_case_spaceships_uri_file:50322a7173b6976c'
component.inputs["spaceship_data"].mode  # 'ro_mount'

Notes / follow-up

• Only string asset or path references are accepted; a nested Input object as default is not introduced, since the wire contract carries a string.
• The public YAML reference docs and the azuremlschemas.azureedge.net schemas live outside this repo and should be aligned separately.

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