swc-project/swc · error

CARGO_MANIFEST_DIR

Error message

CARGO_MANIFEST_DIR

What it means

`test_inlined_transform` (crates/swc_ecma_transforms_testing/src/lib.rs) resolves the snapshot directory from `std::env::var("CARGO_MANIFEST_DIR")`. The `expect("CARGO_MANIFEST_DIR")` panics when the environment variable is absent — i.e. the test code is running outside a normal `cargo test` invocation, since cargo always sets this variable for build/test runs.

Source

Thrown at crates/swc_ecma_transforms_testing/src/lib.rs:407

    );
}

/// NOT A PUBLIC API. DO NOT USE.
#[doc(hidden)]
#[track_caller]
pub fn test_inlined_transform<F, P>(
    test_name: &str,
    syntax: Syntax,
    module: Option<bool>,
    tr: F,
    input: &str,
) where
    F: FnOnce(&mut Tester) -> P,
    P: Pass,
{
    let loc = panic::Location::caller();

    let manifest_dir = PathBuf::from(env::var("CARGO_MANIFEST_DIR").expect("CARGO_MANIFEST_DIR"));

    let test_file_path = CARGO_WORKSPACE_ROOT.join(loc.file());

    let snapshot_dir = manifest_dir.join("tests").join("__swc_snapshots__").join(
        test_file_path
            .strip_prefix(&manifest_dir)
            .expect("test_inlined_transform does not support paths outside of the crate root"),
    );

    test_fixture_inner(
        syntax,
        Box::new(move |tester| Box::new(tr(tester))),
        input,
        &snapshot_dir.join(format!("{test_name}.js")),
        FixtureTestConfig {
            module,
            ..Default::default()
        },

View on GitHub (pinned to 5176682b65)

Solutions

1. Run the tests through cargo: `cargo test -p <crate> <test_name>` so cargo exports CARGO_MANIFEST_DIR.
2. If you must run the binary directly, export the variable first: `CARGO_MANIFEST_DIR=$(pwd) ./target/debug/deps/...`.
3. For IDE/runner integrations, configure them to preserve cargo's environment (rust-analyzer and `cargo nextest` do this by default).

Example fix

// before
$ ./target/debug/deps/mycrate-abc123 inline_test  # env missing -> panic

// after
$ cargo test -p mycrate inline_test

// Guard inlined-transform tests against non-cargo execution.
fn cargo_env_ok() -> bool {
    std::env::var("CARGO_MANIFEST_DIR").is_ok()
}

When it happens

Trigger: Executing the compiled test binary directly (e.g. `./target/debug/deps/foo-... `), running tests under a runner or IDE that scrubs the environment, or invoking the test harness from a non-cargo context (custom scripts, some remote-test setups).

Common situations: Debugging a single test by running the binary from a shell; CI wrappers that sanitize env; `cargo test` replaced by direct binary execution in benchmarks or probes.

Understand the failure class

Background: "environment variable is not set" and "Missing keys in environment" errors: what missing required env var messages mean and how to fix them — this error's family across 28 libraries.

Related errors

• failed to execute transfomred code
• test_inlined_transform does not support paths outside of the
• failed to get current directory
• failed to read file
• failed to create parent directory for temp directory

AI-assisted analysis of swc-project/swc@5176682b65 (2026-08-17). Data as JSON: /api/errors/38611686a5cf04e7. Report an issue: GitHub.