Built-in generation plugin for the @include and @skip directives.

A conditionally-selected field may be omitted from the response, so its generated type must be nullable even when the schema says the field is non-null. Runtime decode already tolerates the omission; this plugin only fixes generated-type accuracy.

After the normalize step has propagated ancestor (inline-fragment / fragment-spread) directives onto each field, this plugin walks the resolved tree and marks every conditionally-selected field nullable.

Conditionality

A directive's if: argument is a TypedGql.Language.Variable or a literal TypedGql.Language.BooleanValue:

• @include(if: $var) / @skip(if: $var) — conditional (variable).
• @include(if: true) / @skip(if: false) — no-op, not conditional.
• @include(if: false) / @skip(if: true) — always omitted, but still generated as nullable to keep the struct shape stable.

So @include is conditional unless if: is literal true, and @skip is conditional unless if: is literal false.

A [T!]! object list is generated as embeds_many, which is forced to default: [] downstream and so cannot represent whole-absence as nil; its nullability is left unchanged (see the type generator docs). Every other list shape is a plain field and is marked nullable like any other.