🐛 Fix inconsistent processing of model docstring formfeed char with Pydantic V1 (#6039)

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Yurii Motov <yurii.motov.monte@gmail.com>
Co-authored-by: Sebastián Ramírez <tiangolo@gmail.com>

fastapi/_compat.py

@@ -393,9 +393,10 @@ else:
             )
             definitions.update(m_definitions)
             model_name = model_name_map[model]
+            definitions[model_name] = m_schema
+        for m_schema in definitions.values():
             if "description" in m_schema:
                 m_schema["description"] = m_schema["description"].split("\f")[0]
-            definitions[model_name] = m_schema
         return definitions
 
     def is_pv1_scalar_field(field: ModelField) -> bool:

tests/test_get_model_definitions_formfeed_escape.py

@@ -0,0 +1,180 @@
+from typing import Any, Iterator, Set, Type
+
+import fastapi._compat
+import fastapi.openapi.utils
+import pydantic.schema
+import pytest
+from fastapi import FastAPI
+from pydantic import BaseModel
+from starlette.testclient import TestClient
+
+from .utils import needs_pydanticv1
+
+
+class Address(BaseModel):
+    """
+    This is a public description of an Address
+    \f
+    You can't see this part of the docstring, it's private!
+    """
+
+    line_1: str
+    city: str
+    state_province: str
+
+
+class Facility(BaseModel):
+    id: str
+    address: Address
+
+
+app = FastAPI()
+
+client = TestClient(app)
+
+
+@app.get("/facilities/{facility_id}")
+def get_facility(facility_id: str) -> Facility: ...
+
+
+openapi_schema = {
+    "components": {
+        "schemas": {
+            "Address": {
+                # NOTE: the description of this model shows only the public-facing text, before the `\f` in docstring
+                "description": "This is a public description of an Address\n",
+                "properties": {
+                    "city": {"title": "City", "type": "string"},
+                    "line_1": {"title": "Line 1", "type": "string"},
+                    "state_province": {"title": "State Province", "type": "string"},
+                },
+                "required": ["line_1", "city", "state_province"],
+                "title": "Address",
+                "type": "object",
+            },
+            "Facility": {
+                "properties": {
+                    "address": {"$ref": "#/components/schemas/Address"},
+                    "id": {"title": "Id", "type": "string"},
+                },
+                "required": ["id", "address"],
+                "title": "Facility",
+                "type": "object",
+            },
+            "HTTPValidationError": {
+                "properties": {
+                    "detail": {
+                        "items": {"$ref": "#/components/schemas/ValidationError"},
+                        "title": "Detail",
+                        "type": "array",
+                    }
+                },
+                "title": "HTTPValidationError",
+                "type": "object",
+            },
+            "ValidationError": {
+                "properties": {
+                    "loc": {
+                        "items": {"anyOf": [{"type": "string"}, {"type": "integer"}]},
+                        "title": "Location",
+                        "type": "array",
+                    },
+                    "msg": {"title": "Message", "type": "string"},
+                    "type": {"title": "Error Type", "type": "string"},
+                },
+                "required": ["loc", "msg", "type"],
+                "title": "ValidationError",
+                "type": "object",
+            },
+        }
+    },
+    "info": {"title": "FastAPI", "version": "0.1.0"},
+    "openapi": "3.1.0",
+    "paths": {
+        "/facilities/{facility_id}": {
+            "get": {
+                "operationId": "get_facility_facilities__facility_id__get",
+                "parameters": [
+                    {
+                        "in": "path",
+                        "name": "facility_id",
+                        "required": True,
+                        "schema": {"title": "Facility Id", "type": "string"},
+                    }
+                ],
+                "responses": {
+                    "200": {
+                        "content": {
+                            "application/json": {
+                                "schema": {"$ref": "#/components/schemas/Facility"}
+                            }
+                        },
+                        "description": "Successful Response",
+                    },
+                    "422": {
+                        "content": {
+                            "application/json": {
+                                "schema": {
+                                    "$ref": "#/components/schemas/HTTPValidationError"
+                                }
+                            }
+                        },
+                        "description": "Validation Error",
+                    },
+                },
+                "summary": "Get Facility",
+            }
+        }
+    },
+}
+
+
+def test_openapi_schema():
+    """
+    Sanity check to ensure our app's openapi schema renders as we expect
+    """
+    response = client.get("/openapi.json")
+    assert response.status_code == 200, response.text
+    assert response.json() == openapi_schema
+
+
+class SortedTypeSet(set):
+    """
+    Set of Types whose `__iter__()` method yields results sorted by the type names
+    """
+
+    def __init__(self, seq: Set[Type[Any]], *, sort_reversed: bool):
+        super().__init__(seq)
+        self.sort_reversed = sort_reversed
+
+    def __iter__(self) -> Iterator[Type[Any]]:
+        members_sorted = sorted(
+            super().__iter__(),
+            key=lambda type_: type_.__name__,
+            reverse=self.sort_reversed,
+        )
+        yield from members_sorted
+
+
+@needs_pydanticv1
+@pytest.mark.parametrize("sort_reversed", [True, False])
+def test_model_description_escaped_with_formfeed(sort_reversed: bool):
+    """
+    Regression test for bug fixed by https://github.com/fastapi/fastapi/pull/6039.
+
+    Test `get_model_definitions` with models passed in different order.
+    """
+    all_fields = fastapi.openapi.utils.get_fields_from_routes(app.routes)
+
+    flat_models = fastapi._compat.get_flat_models_from_fields(
+        all_fields, known_models=set()
+    )
+    model_name_map = pydantic.schema.get_model_name_map(flat_models)
+
+    expected_address_description = "This is a public description of an Address\n"
+
+    models = fastapi._compat.get_model_definitions(
+        flat_models=SortedTypeSet(flat_models, sort_reversed=sort_reversed),
+        model_name_map=model_name_map,
+    )
+    assert models["Address"]["description"] == expected_address_description