MongoDB Schema Validation Rules

This rule applies to files matching the patterns above.

# MongoDB Schema Validation Rules

## Rule
Every production collection MUST have JSON Schema validation to enforce document structure, required fields, and data types.

## Format
```javascript
db.createCollection("collectionName", {
  validator: { $jsonSchema: { /* schema */ } },
  validationLevel: "strict",
  validationAction: "error"
});
```

## Requirements

### 1. Define Schema for Every Collection
```javascript
db.createCollection("users", {
  validator: {
    $jsonSchema: {
      bsonType: "object",
      required: ["email", "name", "role", "createdAt"],
      properties: {
        email: {
          bsonType: "string",
          pattern: "^[a-zA-Z0-9._%+-]+@[a-zA-Z0-9.-]+\\.[a-zA-Z]{2,}$",
          description: "Must be a valid email address"
        },
        name: {
          bsonType: "string",
          minLength: 2,
          maxLength: 100
        },
        role: {
          bsonType: "string",
          enum: ["admin", "user", "moderator"]
        },
        profile: {
          bsonType: "object",
          properties: {
            bio: { bsonType: "string", maxLength: 500 },
            avatarUrl: { bsonType: "string" }
          }
        },
        createdAt: { bsonType: "date" },
        updatedAt: { bsonType: "date" }
      },
      additionalProperties: false
    }
  },
  validationLevel: "strict",
  validationAction: "error"
});
```

### 2. Add schemaVersion to Documents
```javascript
// Include version for schema evolution
{
  _id: ObjectId("..."),
  schemaVersion: 2,
  email: "user@example.com",
  name: "Jane Smith",
  role: "user",
  createdAt: ISODate("2025-01-01")
}
```

### 3. Validate Nested Documents
```javascript
properties: {
  address: {
    bsonType: "object",
    required: ["street", "city", "country"],
    properties: {
      street: { bsonType: "string" },
      city: { bsonType: "string" },
      state: { bsonType: "string" },
      country: { bsonType: "string" },
      postalCode: { bsonType: "string" }
    }
  }
}
```

## Examples

### Good
```javascript
// Strict validation catches bad data at write time
db.users.insertOne({ email: "invalid", name: "J", role: "superadmin" });
// Error: Document failed validation
```

### Bad
```javascript
// No validation — any shape of document is accepted
db.users.insertOne({ foo: "bar", random: 42 });
// Succeeds — data integrity is lost
```

## Enforcement
Add schema validation as part of collection creation scripts in your migration pipeline. Use validationLevel "strict" for new collections and "moderate" during migration periods.