[PRABHU KIRAN VANDRANKI (VANDRANKI)]

Motivation and Context

KernelJsonSchemaBuilder had no handling for typing.Literal. A parameter typed Literal["fast", "slow"] was advertised to the model as a bare {"type": "object"} with no enum, so the model was never told the allowed values. This also hit Pydantic fields, Optional[Literal[...]] and list[Literal[...]].

Fixes #14511

Description

In handle_complex_type, a Literal now builds {"type": ..., "enum": [...]}, the same shape build_enum_schema returns for Enum classes:

• type is the JSON type of the values when they all share one, otherwise a list of the types (with "null" last). None maps to "null".
• Enum members inside a Literal are converted to their .value.
• Optional[Literal[...]] (and Literal[...] | None) now adds "null" to type and None to enum. The Optional branch also no longer nests a list inside type when the inner schema already has a list type.
• list[Literal[...]] works through the existing list branch and puts the enum on items.

Tests added in tests/unit/schema/test_schema_builder.py cover str, int, bool, mixed, Optional, | None, list, Enum members, descriptions, and a Pydantic model with Literal fields. The new tests fail on current main and pass now.

tests/unit/schema, tests/unit/functions, tests/unit/connectors/utils and test_function_choice_behavior.py: all pass. ruff and mypy are clean on the changed files. The repro from the issue now gives {"type": "string", "enum": ["fast", "slow"], "description": "speed mode"} for mode and an enum on the nested level field.

Contribution Checklist

• The code builds clean without any errors or warnings
• The PR follows the SK Contribution Guidelines and the pre-submission formatting script raises no violations
• All unit tests pass, and I have added new tests where possible
• I didn't break anyone 😄

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