facebook/flow · error

File_key: flowlib_root has not been set

Error message

File_key: flowlib_root has not been set

What it means

Same pattern as the project root: get_flowlib_root expects Some from the global FLOWLIB_ROOT RwLock and panics when set_flowlib_root was never called. The flowlib root anchors resolution of flowlib/ and tslib/ imports, so FileKey operations on lib files hit this getter immediately when uninitialized.

Source

Thrown at rust_port/crates/flow_parser/src/file_key.rs:194

}

// Retrieve a root, crashing immediately if not set. Following Hack's
// Relative_path convention: an unset root is a programmer error that
// should be caught at the call site, not masked downstream.
pub fn get_project_root() -> String {
    PROJECT_ROOT
        .read()
        .unwrap()
        .clone()
        .expect("File_key: project_root has not been set")
}

pub fn get_flowlib_root() -> String {
    FLOWLIB_ROOT
        .read()
        .unwrap()
        .clone()
        .expect("File_key: flowlib_root has not been set")
}

fn is_relative(path: &str) -> bool {
    std::path::Path::new(path).is_relative()
}

// libs, then source and json files at the same priority since JSON files are
// basically source files. We don't actually read resource files so they come
// last
fn order_of_inner(inner: &FileKeyInner) -> i32 {
    match inner {
        FileKeyInner::LibFile(_) => 1,
        FileKeyInner::SourceFile(_) => 2,
        FileKeyInner::JsonFile(_) => 2,
        FileKeyInner::ResourceFile(_) => 3,
    }
}

View on GitHub (pinned to f88ac94bcf)

Solutions

1. Call set_flowlib_root right after set_project_root in the shared init function
2. Add a startup assertion (call get_flowlib_root once at boot) so misconfiguration fails fast with your own message
3. Review every binary/test entry point after moving initialization code

Example fix

// before — panics: flowlib root never set
let fk = FileKey::flowlib_file(&name);

// after — set both roots during startup
flow_parser::file_key::set_project_root(&format!("{}/", root.display()));
flow_parser::file_key::set_flowlib_root(&flowlib_dir.to_string_lossy());
let fk = FileKey::flowlib_file(&name);

// Both roots, one init — call before creating any FileKey
pub fn init_file_keys(project_root: &str, flowlib_root: &str) {
    flow_parser::file_key::set_project_root(project_root);
    flow_parser::file_key::set_flowlib_root(flowlib_root);
}

When it happens

Trigger: Constructing or relativizing lib-file FileKeys (flowlib imports, tslib resolution) before set_flowlib_root; tests that set only the project root; binaries reusing parser APIs without the full startup sequence.

Common situations: New test binaries wired up with half the initialization; refactors that dropped the flowlib setup call; embedding flow_parser where the caller only configured a project root.

Related errors

• File_key: project_root has not been set
• failed to write flowlib file
• init failed: {:?}
• lock file is already held
• invalid line

AI-assisted analysis of facebook/flow@f88ac94bcf (2026-08-20). Data as JSON: /api/errors/d87aefbb325d3b4f. Report an issue: GitHub.