Naming and Validation

Why Naming Matters

VDL schemas are used to generate code in different languages. Consistent names make generated output predictable and pleasant to use.

The analyzer reports diagnostics when names do not follow the expected convention.

PascalCase starts with an uppercase letter and does not use underscores.

Good:

type UserProfile {
  displayName string
}

enum OrderStatus {
  Pending
}

Avoid:

type user_profile {
  displayName string
}

camelCase starts with a lowercase letter and does not use underscores.

Good:

type UserProfile {
  displayName string
  createdAt datetime
}

const maxPageSize = 100

Avoid:

type UserProfile {
  display_name string
}

const MaxPageSize = 100

Regular schema files should match:

[a-z0-9_]+.vdl

Examples:

schema.vdl
shared_types.vdl
events_v1.vdl

The configuration file must be named:

vdl.config.vdl

Top-level type, enum, and constant names share one global namespace.

Invalid:

type Status string

enum Status {
  Active
}

Use unique names across declarations.

Fields must be unique within each object or inline object.

Invalid:

type User {
  id string
  id int
}

Every type reference must point to a declared type, enum, or primitive.

Invalid:

type User {
  address Address
}

Fix it by declaring Address or including the file that declares it.

type Address {
  city string
}

type User {
  address Address
}

VDL rejects required type cycles.

Invalid:

type Parent {
  child Child
}

type Child {
  parent Parent
}

Break the cycle with an optional field.

type Parent {
  child Child
}

type Child {
  parent? Parent
}

Before generating code, check that: