---
url: /docs/5.x/guide/concepts/generators.md
description: >-
  A generator is the piece of a plugin that walks the AST and emits files. One
  plugin can register several, each handling schemas, single operations, or the
  whole operation set.
---

# Generators

A generator is where a plugin produces code. The plugin handles options, lifecycle, and wiring, while the generator reads a node from the [AST](/docs/5.x/guide/concepts/ast) and returns the files that node becomes. A plugin with no generators emits nothing.

## Why a plugin splits into generators

You could write one big function, but most plugins produce several kinds of output from the same spec. `@kubb/plugin-react-query` writes a hook per operation, a query key per operation, and a barrel once everything is done. Splitting that into named generators keeps each one small and lets the engine call the right generator for each node, instead of one function branching on everything it might see.

A plugin registers its generators during [plugin setup](/docs/5.x/guide/concepts/plugins). After that, the engine owns the schedule, walking the AST once and calling each generator's methods as the matching nodes come up.

## What each method handles

A generator implements up to three methods, each for a different slice of the spec: `schema` for one data schema at a time, `operation` for one API operation at a time, and `operations` once with the whole set, for output like an index or a router that needs to see everything before it writes anything. See the [generator methods table](/docs/5.x/reference/kit/generators#generator-methods) for what each one returns and exactly when it runs.

Each method receives the generator context and returns the files that node becomes. It can hand back file nodes directly, return a renderer element, or write through the context and return nothing. The [generator reference](/docs/5.x/reference/kit/generators) lists every field on that context.

## Scoping a generator with `match`

A plugin sometimes registers several generators for the same node type, where only one should run per node, for example one hook generator per query variant. Give a generator a `match(node, ctx)` predicate to declare that scope: when it returns `false`, the engine skips `schema` or `operation` for that node entirely, instead of calling the generator only to have it classify the node and bail out itself. See the [generator reference](/docs/5.x/reference/kit/generators#match) for the full signature.