pydantic 2.8.2: BaseModel

Clean-room public code sample — generation instructions

Write a brand-new, minimal, self-contained code sample in this clean-room directory.
Do not copy, paraphrase, or reference any existing project source. Work only from this spec.

A csx.json manifest scaffold already exists. Do not recreate it from memory. Preserve its case.goal, packages and symbols; fill its empty case.contract with exact assertions and correct its environment, commands and verifierAdapter for the files you generate.

Goal: verify pydantic.BaseModel in pkg:pypi/pydantic@2.8.2
Kind: HOW

Use EXACTLY these public packages and versions:
  - pkg:pypi/pydantic@2.8.2
Demonstrate these symbols/APIs:
  - pydantic.BaseModel
Required runtime conditions:
  - ecosystem: golang
  - language: go
  - packageManager: go@1.26.5
  - runtime: go@1.26.5

Rules:
  - One focused purpose; the smallest project that proves the goal.
  - Include a contract test (test/contract.*) that runs OFFLINE and exits 0 exactly when the goal behavior works.
  - Pin every dependency with a lockfile so resolution is reproducible.
  - No secrets, credentials, or tokens. No real URLs (only example.com or localhost). No absolute paths.
  - No personal names, emails, company names, or project identifiers of any kind.
  - No binaries and no generated output (node_modules, dist, target, venv, .git, .env).
  - Keep it under 200 files and 256KB packed.

{"case":{"caseId":"case:sha256:d9ec81d127d57bbf50df0c07c117c6037dfa1644911c0630dca50b77a977ad8b","contract":["pydantic.BaseModel parses, coerces, and validates typed model fields.","BaseModel.model_dump and model_dump_json serialize instances to dict and JSON format.","BaseModel.model_validate deserializes and validates dict inputs.","ValidationError is raised on invalid field types or constraint violations."],"goal":"verify pydantic.BaseModel in pkg:pypi/pydantic@2.8.2","kind":"HOW","packages":["pkg:pypi/pydantic@2.8.2"],"schemaVersion":1,"symbols":["pydantic.BaseModel"]},"contractCommand":["python","test/contract.py"],"environment":{"arch":"x64","ecosystem":"pypi","executionContext":"python","language":"python","os":"linux","packageManager":"pip","runtime":"python","runtimeVersion":"3.12","schemaVersion":1},"license":"MIT-0","packages":["pkg:pypi/pydantic@2.8.2"],"schemaVersion":1,"symbols":["pydantic.BaseModel"],"verifierAdapter":"python@1"}

annotated-types==0.8.0
pydantic==2.8.2
pydantic-core==2.20.1
typing-extensions==4.16.0

{
  "schemaVersion": 1,
  "goal": "verify pydantic.BaseModel in pkg:pypi/pydantic@2.8.2",
  "kind": "HOW",
  "packages": [
    "pkg:pypi/pydantic@2.8.2"
  ],
  "symbols": [
    "pydantic.BaseModel"
  ],
  "runtimeConditions": {
    "ecosystem": "golang",
    "language": "go",
    "packageManager": "go@1.26.5",
    "runtime": "go@1.26.5"
  }
}

from typing import List, Optional
import pydantic
from pydantic import BaseModel, Field, ValidationError

assert pydantic.__version__ == "2.8.2"

class User(BaseModel):
    id: int
    name: str = Field(min_length=1)
    tags: List[str] = Field(default_factory=list)
    email: Optional[str] = None

# 1. Validation and model instantiation
user = User(id=1, name="Alice", tags=["admin", "staff"])
assert user.id == 1
assert user.name == "Alice"
assert user.tags == ["admin", "staff"]
assert user.email is None

# 2. Serialization with model_dump and model_dump_json
dump = user.model_dump()
assert dump == {"id": 1, "name": "Alice", "tags": ["admin", "staff"], "email": None}

json_str = user.model_dump_json()
assert '"id":1' in json_str or '"id": 1' in json_str

# 3. Deserialization with model_validate and model_validate_json
validated = User.model_validate({"id": 2, "name": "Bob", "tags": ["guest"], "email": "bob@example.com"})
assert validated.id == 2
assert validated.email == "bob@example.com"

# 4. Validation errors on invalid inputs
try:
    User.model_validate({"id": "not-an-int", "name": ""})
    raise AssertionError("Expected ValidationError")
except ValidationError as e:
    errors = e.errors()
    assert len(errors) >= 2

print("CONTRACT PASS: pydantic.BaseModel in pydantic 2.8.2")