> ## Documentation Index
> Fetch the complete documentation index at: https://fastql.vachagan.dev/llms.txt
> Use this file to discover all available pages before exploring further.

# Language pipeline

> Follow GraphQL source through lexing, parsing, and AST production.

The language package is independent of schema construction. `Source` tracks the
query body and location data. The lexer emits GraphQL tokens; the recursive parser
builds nodes from `fastql.language.ast`.

```mermaid theme={null}
flowchart LR
  A[Source text] --> B[Lexer]
  B --> C[Tokens]
  C --> D[Parser]
  D --> E[DocumentNode]
  E --> F[Validation and execution]
  E --> G[Printer]
```

Syntax errors carry source locations and stop execution before schema validation.
A parsed `DocumentNode` can be passed directly to `validate` or `execute`, avoiding
re-parsing for applications that cache documents.

The AST preserves executable definitions, fragments, directives, values, variables,
and type references. Schema definition language output is produced from the compiled
schema model rather than by round-tripping a user-provided SDL document.