fraiseql-cli 2.17.0

//! `fraiseql federation sdl`: a subgraph's federation SDL, from its compiled schema (#1427).
//!
//! Composing a supergraph needs each subgraph's SDL. A running server serves it as
//! `_service { sdl }`; this prints the same text from `schema.compiled.json`, so a
//! composition gate needs neither a booted server nor a principal allowed to call it.

use std::{io::Write as _, path::Path};

use anyhow::{Context, Result};
use fraiseql_core::schema::CompiledSchema;

/// The SDL the server would serve as `_service { sdl }` from the compiled schema at
/// `schema_path`: the same function renders both.
///
/// # Errors
///
/// The file cannot be read or is not a compiled schema, or its `[federation]` section is
/// absent or disabled.
pub fn render(schema_path: &Path) -> Result<String> {
    let json = std::fs::read_to_string(schema_path)
        .with_context(|| format!("failed to read {}", schema_path.display()))?;
    let schema = CompiledSchema::from_json(&json, false)
        .with_context(|| format!("{} is not a compiled schema", schema_path.display()))?;
    schema
        .federation_service_sdl()
        .with_context(|| format!("{} is not a federated subgraph", schema_path.display()))
}

/// Print the SDL to stdout, exactly as served, or write it to `output`.
///
/// # Errors
///
/// As [`render`], or `output` cannot be written.
pub fn run(schema_path: &Path, output: Option<&Path>) -> Result<()> {
    let sdl = render(schema_path)?;
    if let Some(path) = output {
        return std::fs::write(path, sdl)
            .with_context(|| format!("failed to write {}", path.display()));
    }
    let mut stdout = std::io::stdout().lock();
    stdout.write_all(sdl.as_bytes()).context("failed to write the SDL to stdout")?;
    stdout.flush().context("failed to write the SDL to stdout")
}