[python] Add models-mode "typeddict" for input-only TypedDict model generation

[Copilot]

Implements alpha TypedDict support for issue #8800. Enables generating Python TypedDict classes instead of runtime model classes for input-only scenarios.

Changes

TypeScript Emitter

• Added "typeddict" to models-mode option enum in PythonEmitterOptions
• Updated emitModel() to dynamically set model base field from options

Python Generator

• Created TypedDictModelType class - serializes as plain dict, uses isinstance(x, dict) checks
• Created TypedDictModelSerializer - generates TypedDict classes with total=False for optional properties
• Added model_typeddict.py.jinja2 template
• Updated serializer dispatch in __init__.py and builder_serializer.py to handle typeddict mode
• Unified dpg/typeddict body parameter serialization logic (both use JSON serialization without runtime model base)

Usage

# tspconfig.yaml
options:
  "@typespec/http-client-python":
    models-mode: "typeddict"

Generates:

from typing import TypedDict

class User(TypedDict, total=False):
    name: str
    age: int
    email: str

# Used as input type hints, serialized as plain dict
def create_user(user: User) -> dict: ...

Limitations (Alpha)

• Input-only (outputs return raw JSON/dict)
• Supports: boolean, int, string, enum, list, dict
• No support for: discriminators, readonly, datetime, bytes, record extension

Warning

Firewall rules blocked me from connecting to one or more addresses (expand for details)

I tried to connect to the following addresses, but was blocked by firewall rules:

• telemetry.astro.build

If you need me to access, download, or install something from one of these locations, you can either:

• Configure Actions setup steps to set up my environment, which run before the firewall is enabled
• Add the appropriate URLs or hosts to the custom allowlist in this repository's Copilot coding agent settings (admins only)

Original prompt

---

This section details on the original issue you should resolve

<issue_title>[python] Add new models-mode "typeddict"</issue_title>
<issue_description>Goal:

Add new models-mode "typeddict" for https://github.com/microsoft/typespec/tree/main/packages/http-client-python

Details:

declared in #8800 (comment)
</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes [python] Add new models-mode "typeddict" #8906

---

💬 We'd love your input! Share your thoughts on Copilot coding agent in our 2 minute survey.

[github-actions]

❌ There is undocummented changes. Run chronus add to add a changeset or click here.

The following packages have changes but are not documented.

• ❌@typespec/http-client-python

Show changes

[microsoft-github-policy-service]

Hi @@copilot. Your PR has had no update for 30 days and it is marked as a stale PR. If it is not updated within 30 days, the PR will automatically be closed. If you want to refresh the PR, please remove the stale label.