gleam-lang/gleam · error

invalid folder

Error message

invalid folder

What it means

get_foldername resolves the target folder name for `gleam new .` by reading the process working directory with env::current_dir().expect("invalid folder"). current_dir() fails with io::Error when the process's cwd has been deleted, unmounted, or its permissions revoked, and the expect turns that into a panic before gleam can produce its nicer UnableToFindProjectRoot error. It only triggers for the `.` special case — passing an explicit name/path never calls env::current_dir().

Source

Thrown at compiler-cli/src/new.rs:491

                decided: suggested_name,
            },
            None => ProjectName::Derived {
                folder: initial_name,
                decided: suggested_name,
            },
        });
    }

    Err(Error::InvalidProjectName {
        name: initial_name,
        reason: invalid_reason,
    })
}

fn get_foldername(path: &str) -> Result<String, Error> {
    match path {
        "." => env::current_dir()
            .expect("invalid folder")
            .file_name()
            .and_then(|x| x.to_str())
            .map(ToString::to_string)
            .ok_or(Error::UnableToFindProjectRoot {
                path: path.to_string(),
            }),
        _ => Utf8Path::new(path)
            .file_name()
            .map(ToString::to_string)
            .ok_or(Error::UnableToFindProjectRoot {
                path: path.to_string(),
            }),
    }
}

#[derive(Debug, Clone)]
enum ProjectName {
    Provided { decided: String },

View on GitHub (pinned to 7e623aa83d)

Solutions

1. Re-enter an existing directory in the same shell: `cd .` will fail, so `cd ~` (or restart the shell), then cd into the recreated directory and rerun `gleam new .`.
2. Recreate the directory if it was deleted: `mkdir -p /path/to/dir && cd /path/to/dir && gleam new .`.
3. Avoid the `.` path entirely: run `gleam new my_project` from a parent directory, which uses Utf8Path::file_name() and never touches current_dir().

Example fix

# before: shell sits in a deleted directory
cd /tmp/gone_project   # (dir deleted elsewhere)
gleam new .            # panics: env::current_dir() fails

# after: recreate/refresh the cwd first
mkdir -p /tmp/gone_project && cd /tmp/gone_project && gleam new .
# or sidestep '.' entirely:
cd /tmp && gleam new gone_project

// Verify the shell's cwd still exists before spawning gleam new
match std::env::current_dir() {
    Ok(dir) if dir.exists() => {}
    _ => { // cd to a known-good dir first, or fail with a clear message
        return Err("working directory was deleted; cd elsewhere".into());
    }
}
// shell equivalent: [ -d "$(pwd -P 2>/dev/null)" ] || cd ~

When it happens

Trigger: Running `gleam new .` (project_root defaults to '.' at new.rs:435) from a shell whose cwd was rm -rf'd in another terminal, a cwd on an unmounted network drive or dead container mount, or a cwd the user can no longer stat due to permission changes.

Common situations: A rebuild script deleted and recreated the project directory while the shell stayed inside the old inode; tmux/ssh sessions resumed after their directory was removed; CI steps running in a scratch dir cleaned by a parallel job.

Related errors

• `panic` expression evaluated.
• Non Utf-8 Path
• Non-UTF8 path in hardlink_dir
• Writing warning to stderr
• Final result error writing

AI-assisted analysis of gleam-lang/gleam@7e623aa83d (2026-08-17). Data as JSON: /api/errors/9f4642a909b86d91. Report an issue: GitHub.