Function mountFuse

packages/computerd/src/fuse/driver.ts:959–1049

(options: {
  backend?: FUSEBackend;
  mountPoint: string;
  vfs: NodeVirtualFileSystem;
})

}

export async function mountFuse(options: {
  backend?: FUSEBackend;
  mountPoint: string;
  vfs: NodeVirtualFileSystem;
}): Promise<FuseMount> {
  // biome-ignore lint/suspicious/noExplicitAny: fuse-native ships no types
  const fuseModule: any = await import("fuse-native");
  const Fuse = fuseModule.default ?? fuseModule;
  // Optional op tracing. `COMPUTERD_FUSE_TRACE=summary` records per-op call
  // counts and timings; the summary is emitted on SIGUSR2 and on
  // unmount, to stderr by default or to `COMPUTERD_FUSE_TRACE_FILE` when set.
  // Disabled means zero wrapping overhead — the unwrapped ops object
  // is handed to fuse-native directly.
  const traceMode = process.env.COMPUTERD_FUSE_TRACE;
  const tracer: FuseTracer | undefined = traceMode === "summary" ? createFuseTracer() : undefined;
  const baseOps = makeFUSEOps(options.vfs, options.mountPoint);
  const { getBufferStats: _getBufferStats, ...fuseOps } = baseOps;
  const ops =
    tracer === undefined
      ? fuseOps
      : wrapFuseOpsWithTracer(fuseOps as unknown as Record<string, unknown>, tracer);
  const fuse = new Fuse(options.mountPoint, ops, {
    autoUnmount: true,
    debug: false,
  }) as FuseNativeInstance;

  const emitTrace = (reason: string): void => {
    if (tracer === undefined) return;
    const json = tracer.formatJson();
    const target = process.env.COMPUTERD_FUSE_TRACE_FILE;
    if (target !== undefined && target !== "") {
      try {
        nodeWriteFileSync(target, `${json}\n`);
      } catch (error) {
        process.stderr.write(
          `computerd: failed to write FUSE trace to ${target} (${reason}): ${String(error)}\n${json}\n`,
        );
      }
      return;
    }
    process.stderr.write(`computerd: FUSE trace (${reason})\n${json}\n`);
  };

  if (tracer !== undefined) {
    process.on("SIGUSR2", () => emitTrace("SIGUSR2"));
  }

  // fuse-native (libfuse 2.9) doesn't expose big_writes/max_write/max_read
  // through opts, so monkey-patch _fuseOptions() to append them. big_writes
  // lets the kernel batch up to max_write bytes per FUSE op instead of the
  // default 4 KiB, cutting per-op round-trips ~32x on large sequential I/O.
  // buildFuseOptionString reads COMPUTERD_FUSE_* env vars; with none set it
  // emits the production-safe profile (auto_cache plus one-second
  // metadata timeouts) backed by the auto_cache contract tests.
  const origFuseOptions = fuse._fuseOptions.bind(fuse);
  const extraOpts = buildFuseOptionString(process.env);
  fuse._fuseOptions = (): string => {
    const base = origFuseOptions();