{
  "id": "python/pydantic-alias-population",
  "signature": "pydantic_core._pydantic_core.ValidationError: 1 validation error for User\nuserName\n  Field required [type=missing, input_value={'user_name': 'a'}, input_type=dict]",
  "signature_zh": "pydantic_core._pydantic_core.ValidationError：1 个验证错误（User）\nuserName\n  字段必填 [type=missing, input_value={'user_name': 'a'}, input_type=dict]",
  "regex": "pydantic_core\\._pydantic_core\\.ValidationError:\\ 1\\ validation\\ error\\ for\\ User\\\nuserName\\\n\\ \\ Field\\ required\\ \\[type=missing,\\ input_value=\\{'user_name':\\ 'a'\\},\\ input_type=dict\\]",
  "domain": "python",
  "category": "config_error",
  "subcategory": null,
  "root_cause": "Field declared with alias='userName' but input dict uses the Python name 'user_name'. populate_by_name was not enabled.",
  "root_cause_type": "generic",
  "root_cause_zh": "字段声明了 alias='userName'，但输入字典使用 Python 名 'user_name'。未启用 populate_by_name。",
  "versions": [
    {
      "version": "2.x",
      "introduced": null,
      "deprecated": null,
      "removed": null,
      "behavior_change": null,
      "status": "active"
    }
  ],
  "os_specific": {},
  "dead_ends": [
    {
      "action": "",
      "why_fails": "Violates PEP 8 and breaks all Python call sites using user_name.",
      "fail_rate": 0.5,
      "condition": "",
      "sources": []
    },
    {
      "action": "",
      "why_fails": "Pydantic raises a name conflict error at class definition time.",
      "fail_rate": 0.65,
      "condition": "",
      "sources": []
    },
    {
      "action": "",
      "why_fails": "Every caller must know the alias; error-prone and hides schema drift.",
      "fail_rate": 0.55,
      "condition": "",
      "sources": []
    }
  ],
  "workarounds": [
    {
      "action": "",
      "success_rate": 0.95,
      "how": "from pydantic import BaseModel, Field, ConfigDict\nclass User(BaseModel):\n    model_config = ConfigDict(populate_by_name=True)\n    user_name: str = Field(alias='userName')",
      "condition": "",
      "sources": []
    },
    {
      "action": "",
      "success_rate": 0.9,
      "how": "from pydantic import BaseModel, Field, AliasChoices\nclass User(BaseModel):\n    user_name: str = Field(validation_alias=AliasChoices('userName', 'user_name'))",
      "condition": "",
      "sources": []
    }
  ],
  "workarounds_zh": [],
  "transition_graph": {
    "leads_to": [],
    "preceded_by": [],
    "frequently_confused_with": []
  },
  "official_doc_url": null,
  "official_doc_section": null,
  "error_code": null,
  "verification_tier": "ai_generated",
  "confidence": 0.88,
  "fix_success_rate": 0.8,
  "resolvable": "true",
  "first_seen": "2024-03-30",
  "last_confirmed": "2025-01-01",
  "last_updated": "2025-01-01",
  "evidence_count": 0,
  "tags": [],
  "locale": "en",
  "aliases": []
}