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[python] gate TypedDict body overloads behind models-mode typeddict #6

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[python] gate TypedDict body overloads behind models-mode typeddict #6

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2 changes: 1 addition & 1 deletion .chronus/changes/python-addTypedDict-2026-3-21-17-47-3.md
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Expand Up @@ -5,4 +5,4 @@ packages:
- "@typespec/http-client-python"
---

[python] Always generate `TypedDict` typing hints for input models in the `types.py` file, and named union aliases in the `_unions.py` file
[python] Add a `models-mode: typeddict` option that generates `TypedDict` typing hints for input models in the `types.py` file. Also generate named union aliases in the `_unions.py` file (renamed from `_types.py`). `TypedDict` generation is scoped to `models-mode: typeddict`; the default `dpg` mode output is unchanged.
80 changes: 45 additions & 35 deletions packages/http-client-python/generator/pygen/preprocess/__init__.py
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Expand Up @@ -373,42 +373,53 @@ def add_body_param_type(
if not (self.is_tsp and has_multi_part_content_type(body_parameter)) and not is_typeddict_only:
body_parameter["type"]["types"].append(KNOWN_TYPES["binary"])

# Add typeddict overload for non-spread dpg models
if self.options["models-mode"] == "dpg" and is_dpg_model:
cross_lang_id = model_type.get("crossLanguageDefinitionId")
existing_td = self._find_existing_typeddict(code_model, cross_lang_id)
self._insert_typeddict_overload(code_model, body_parameter, model_type, origin_type, existing_td)

# For spread bodies (json base), add a typeddict overload that references
# the original model. This replaces the JSON single-body overload.
if is_json_model:
cross_lang_id = model_type.get("crossLanguageDefinitionId")
original = None
if cross_lang_id:
original = next(
(
t
for t in code_model["types"]
if t.get("type") == "model"
and t.get("crossLanguageDefinitionId") == cross_lang_id
and t is not model_type
),
None,
)

if is_typeddict_only and original:
# In typeddict-only mode, the original dpg model already renders
# as a TypedDict — reference it directly, no copy needed.
if origin_type == "model":
body_parameter["type"]["types"].insert(1, original)
# TypedDict overloads are only generated in ``models-mode: typeddict``.
# In ``dpg`` mode we keep the historical behavior of accepting either the
# generated model or a raw JSON object, so we never emit a ``_types.X``
# reference that has no matching definition in ``types.py``.
if is_typeddict_only:
# A plain model body needs no extra overload: the dpg model already
# renders as a TypedDict, so the single body type collapses to it.
# For spread bodies (json base), add a typeddict overload that
# references the original model, replacing the JSON single-body overload.
if is_json_model:
cross_lang_id = model_type.get("crossLanguageDefinitionId")
original = None
if cross_lang_id:
original = next(
(
t
for t in code_model["types"]
if t.get("type") == "model"
and t.get("crossLanguageDefinitionId") == cross_lang_id
and t is not model_type
),
None,
)

if original:
# The original dpg model already renders as a TypedDict —
# reference it directly, no copy needed.
if origin_type == "model":
body_parameter["type"]["types"].insert(1, original)
else:
td_list_or_dict = copy.deepcopy(body_parameter["type"]["types"][0])
td_list_or_dict["elementType"] = original
body_parameter["type"]["types"].insert(1, td_list_or_dict)
else:
td_list_or_dict = copy.deepcopy(body_parameter["type"]["types"][0])
td_list_or_dict["elementType"] = original
body_parameter["type"]["types"].insert(1, td_list_or_dict)
existing_td = self._find_existing_typeddict(code_model, cross_lang_id)
self._insert_typeddict_overload(
code_model, body_parameter, model_type, origin_type, existing_td
)
elif self.options["models-mode"] == "dpg" and is_dpg_model:
if origin_type == "model":
body_parameter["type"]["types"].insert(1, KNOWN_TYPES["any-object"])
else:
source = original or model_type
existing_td = self._find_existing_typeddict(code_model, cross_lang_id)
self._insert_typeddict_overload(code_model, body_parameter, source, origin_type, existing_td)
# dict or list
# copy the original dict / list type
any_obj_list_or_dict = copy.deepcopy(body_parameter["type"]["types"][0])
any_obj_list_or_dict["elementType"] = KNOWN_TYPES["any-object"]
body_parameter["type"]["types"].insert(1, any_obj_list_or_dict)

if len(body_parameter["type"]["types"]) == 1:
# Only one body variant remains (e.g. typeddict-only mode where the
Expand All @@ -420,7 +431,6 @@ def add_body_param_type(

code_model["types"].append(body_parameter["type"])


def pad_reserved_words(self, name: str, pad_type: PadType, yaml_type: dict[str, Any]) -> str:
# we want to pad hidden variables as well
if not name:
Expand Down
18 changes: 16 additions & 2 deletions packages/http-client-python/tests/unit/test_typeddict_overloads.py
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Expand Up @@ -88,15 +88,29 @@ def test_typeddict_only_single_body_emits_no_overload():


def test_dpg_mode_still_emits_multiple_overloads():
"""Regression guard: dpg mode keeps its binary + typeddict overloads."""
"""Regression guard: dpg mode keeps its binary + JSON overloads."""
plugin = _plugin("dpg")
code_model, yaml_data, _ = _json_model_operation()
body_parameter = yaml_data["bodyParameter"]

plugin.add_body_param_type(code_model, body_parameter)
add_overloads_for_body_param(yaml_data)

# dpg mode adds at least the binary overload alongside the model, so the
# dpg mode adds the binary + raw JSON overloads alongside the model, so the
# combined type has multiple members and overloads are generated.
assert body_parameter["type"]["type"] == "combined"
assert len(yaml_data["overloads"]) >= 2


def test_dpg_mode_emits_no_typeddict_reference():
"""dpg mode must not insert a ``typeddict`` body type (would dangle in types.py)."""
plugin = _plugin("dpg")
code_model, yaml_data, _ = _json_model_operation()
body_parameter = yaml_data["bodyParameter"]

plugin.add_body_param_type(code_model, body_parameter)

member_bases = [t.get("base") for t in body_parameter["type"]["types"]]
assert "typeddict" not in member_bases
# no stray typeddict copy leaked into the shared type list either
assert all(t.get("base") != "typeddict" for t in code_model["types"])
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