{
  "id": "python/pydantic-union-tag-required",
  "signature": "pydantic_core._pydantic_core.ValidationError: 1 validation error for Event\n  Unable to extract tag using discriminator 'kind' [type=union_tag_not_found, input_value={'type': 'click'}, input_type=dict]",
  "signature_zh": "pydantic_core._pydantic_core.ValidationError：1 个验证错误（Event）\n  无法使用鉴别器 'kind' 提取标签 [type=union_tag_not_found, input_value={'type': 'click'}, input_type=dict]",
  "regex": "pydantic_core\\._pydantic_core\\.ValidationError:\\ 1\\ validation\\ error\\ for\\ Event\\\n\\ \\ Unable\\ to\\ extract\\ tag\\ using\\ discriminator\\ 'kind'\\ \\[type=union_tag_not_found,\\ input_value=\\{'type':\\ 'click'\\},\\ input_type=dict\\]",
  "domain": "python",
  "category": "data_error",
  "subcategory": null,
  "root_cause": "A discriminated union expects a discriminator key ('kind') but the input provides a different key ('type').",
  "root_cause_type": "generic",
  "root_cause_zh": "鉴别联合期望鉴别器键（'kind'），但输入提供了不同的键（'type'）。",
  "versions": [
    {
      "version": "2.x",
      "introduced": null,
      "deprecated": null,
      "removed": null,
      "behavior_change": null,
      "status": "active"
    }
  ],
  "os_specific": {},
  "dead_ends": [
    {
      "action": "",
      "why_fails": "Literal values on subclasses still declare kind='click' etc.; tag mismatch persists.",
      "fail_rate": 0.55,
      "condition": "",
      "sources": []
    },
    {
      "action": "",
      "why_fails": "Loses discriminated parsing; downstream isinstance checks become unreliable.",
      "fail_rate": 0.6,
      "condition": "",
      "sources": []
    },
    {
      "action": "",
      "why_fails": "Works but silently mutates payloads; breaks strict round-trip serialization.",
      "fail_rate": 0.4,
      "condition": "",
      "sources": []
    }
  ],
  "workarounds": [
    {
      "action": "",
      "success_rate": 0.95,
      "how": "from typing import Literal, Union, Annotated\nfrom pydantic import BaseModel, Field\nclass Click(BaseModel):\n    type: Literal['click']\n    x: int\nclass View(BaseModel):\n    type: Literal['view']\n    url: str\nEvent = Annotated[Union[Click, View], Field(discriminator='type')]",
      "condition": "",
      "sources": []
    },
    {
      "action": "",
      "success_rate": 0.8,
      "how": "class Click(BaseModel):\n    kind: Literal['click'] = Field(validation_alias=AliasChoices('kind','type'))",
      "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": 0.87,
  "fix_success_rate": 0.8,
  "resolvable": "true",
  "first_seen": "2024-05-19",
  "last_confirmed": "2025-01-01",
  "last_updated": "2025-01-01",
  "evidence_count": 0,
  "tags": [],
  "locale": "en",
  "aliases": []
}