What causes "failed to get current directory" in swc-project/swc?

Pass a real file name when creating the SourceMap entry (parse with `FileName::Real(path)` instead of Anon/Custom).

failed to get current directory

Error message

failed to get current directory

What it means

In the Node-style import path resolver of swc_ecma_transforms_module (crates/swc_ecma_transforms_module/src/path.rs), when the base file is `FileName::Anon` and no `base_dir` is configured in `config`, the resolver falls back to `std::env::current_dir()`. On native targets that call is unwrapped with `expect("failed to get current directory")`, so resolution of an import specifier panics when the OS reports no current directory. On wasm32 the same branch panics with a different message ("Please specify `filename`").

Source

Thrown at crates/swc_ecma_transforms_module/src/path.rs:325

            _ => {
                unreachable!(
                    "Node path provider does not support using `{:?}` as a target file name",
                    target
                )
            }
        };
        let mut base = match base {
            FileName::Real(v) => Cow::Borrowed(
                v.parent()
                    .ok_or_else(|| anyhow!("failed to get parent of {v:?}"))?,
            ),
            FileName::Anon => match &self.config.base_dir {
                Some(v) => Cow::Borrowed(&**v),
                None => {
                    if cfg!(target_arch = "wasm32") {
                        panic!("Please specify `filename`")
                    } else {
                        Cow::Owned(current_dir().expect("failed to get current directory"))
                    }
                }
            },
            _ => {
                unreachable!(
                    "Node path provider does not support using `{:?}` as a base file name",
                    base
                )
            }
        };

        if base.is_absolute() != target.is_absolute() {
            if base.is_absolute() {
                base = Cow::Owned(base.to_path_buf().clean());
            } else {
                base = Cow::Owned(absolute_base_path(self.config.base_dir.as_deref(), &base)?);
            }

View on GitHub (pinned to 5176682b65)

Solutions

Pass a real file name when creating the SourceMap entry (parse with `FileName::Real(path)` instead of Anon/Custom).
Set `base_dir` in the module config (e.g. `Config { base_dir: Some("/project".into()), .. }`) so Anon sources never need the cwd.
If running a long-lived process, ensure its working directory still exists; restart daemons after deleting their cwd.
On wasm32 builds the same misconfiguration panics earlier with "Please specify `filename`" — supply the filename there.

Example fix

// before
let fm = cm.new_source_file(FileName::Anon.into(), src.clone());
// base_dir unset -> resolver calls current_dir()

// after
let fm = cm.new_source_file(
    FileName::Real(PathBuf::from("/project/src/input.js")).into(),
    src.clone(),
);

Defensive patterns

Strategy: validation

Validate before calling

// Before running a module transform with node-style path resolution, ensure
// a base is derivable: real filename OR explicit base_dir OR a valid cwd.
use std::env;

fn module_resolution_preconditions(base_dir: Option<&str>) -> Result<(), String> {
    if base_dir.is_none() && env::current_dir().is_err() {
        return Err("no filename, no base_dir, and cwd unavailable".into());
    }
    Ok(())
}

Prevention

Always parse with a real FileName::Real(path) instead of FileName::Anon when import rewriting will run.
Set module config base_dir for string-based (filename-less) inputs.
In long-lived processes, avoid deleting or invalidating the process cwd.

When it happens

Trigger: Calling a module transform with import rewriting (e.g. `ImportRewriter` / node-style path resolution) on source parsed without a `filename` (FileName::Anon), with `config.base_dir` unset, while the process cwd has been deleted, unlinked, or made unreadable (ENOENT/EACCES from getcwd).

Common situations: Programmatic uses of @swc/core-style APIs that pass a source string with no filename and no `base_dir`, running under a daemon whose cwd was removed (common with some watchers and container setups), or test harnesses that chdir into temp dirs and delete them.

Related errors

AI-assisted analysis of swc-project/swc@5176682b65 (2026-08-17). Data as JSON: /api/errors/88b9f6ce86b5c062. Report an issue: GitHub.