nullable

What It Is

On this page, nullable centers on document-level structure checks, explicit section targeting, and typed field extraction to keep nullable parsing deterministic and schema-driven. The example expects a compact markdown payload and returns top-level keys meta directly from the declared nullable extraction rules. Violations produce issue codes like missing_section, which avoids brittle string checks and keeps nullable failure handling explicit.

When to Use

Choose nullable for tightening scalar constraints without redefining the base shape, especially when nullable authoring rules must remain stable across teams. Skip it in very loose drafts where strict refinement would block iteration workflows for nullable, since key-level strictness that improves typing but rejects ad-hoc variations. Combining it with document(), section(), fields(), and string() yields predictable nullable parsing, clearer errors, and easier runtime integration.

Input Markdown

## 1. META

- Note: null

Schema

import { md } from '@markschema/mdshape'

const schema = md.document({
  meta: md.section('1. META').fields({
    Note: md.string().nullable(),
  }),
})

Result

Success

{
  "success": true,
  "data": {
    "meta": {
      "Note": "null"
    }
  }
}

Error

{
  "success": false,
  "error": {
    "issues": [
      {
        "code": "missing_section",
        "message": "Missing section \"1. META\"",
        "path": [
          "meta"
        ],
        "line": 1,
        "position": {
          "start": {
            "line": 1,
            "column": 1
          }
        }
      }
    ]
  }
}