What causes "should create archive" in gleam-lang/gleam?

Inspect the Err inside create_tar_archive: print it instead of expecting to see the real cause.

should create archive

Error message

should create archive

What it means

In `create_tar_archive_sets_proper_permissions`, the call to the archive-creation helper ends with `.expect("should create archive")`. If building the gzipped tar archive fails (I/O error while writing the in-memory buffer, invalid entry path, etc.), the test panics with this message. Creation is expected to be infallible for the well-formed fixtures used.

Solutions

Inspect the Err inside create_tar_archive: print it instead of expecting to see the real cause.
Verify every OutputFile path is a valid relative tar path (no `..`, no leading `/`).
Check that Content bytes/paths in the fixture match what the function supports.
If the function legitimately can fail, change it to return Result and assert on the error message.

Example fix

// before
.expect("should create archive");
// after
.unwrap_or_else(|err| panic!("should create archive: {err}"));

Defensive patterns

Strategy: try-catch

Validate before calling

// Validate entry paths before archiving
for f in files {
    assert!(!f.path.starts_with('/') && !f.path.components().any(|c| c == ".."), "invalid tar path: {}", f.path);
}

Try / catch

let archive = create_tar_archive(files)
    .unwrap_or_else(|err| panic!("should create archive: {err}"));

Prevention

Inspect the underlying Err rather than hiding it behind a bare expect
Validate all entry paths are relative and free of `..` components before archiving
Keep fixtures aligned with what the archive writer supports
Test create_tar_archive's error paths explicitly in unit tests

When it happens

Trigger: The `create_tar_archive` helper returns Err while compressing the OutputFile list — e.g. an entry path rejected by the tar writer, an I/O failure on the underlying Vec<u8> writer (compiler-cli/src/fs/tests.rs:275).

Common situations: Modifying the archive function or fixtures (e.g. adding a file with an unsupported path like `..` components or an absolute path) and seeing the panic; generally only encountered when changing the tar code or its inputs.

Understand the failure class

Background: "failed to write file", "Could not save figure", "Error saving remote file" — file write failed: causes and fixes across languages and libraries — this error's family across 38 libraries.

Related errors

AI-assisted analysis of gleam-lang/gleam@15b07c7830 (2026-09-14). Data as JSON: /api/errors/d567f524b3f6db1e. Report an issue: GitHub.

Appendix: source

Thrown at compiler-cli/src/fs/tests.rs:275

    assert!(dest.join("real.txt").exists());
    assert!(!dest.join("escape").exists());
}

// https://github.com/gleam-lang/gleam/issues/5992
#[test]
fn create_tar_archive_sets_proper_permissions() {
    let compressed_archive = create_tar_archive(vec![
        OutputFile {
            content: Content::Text("Hello".into()),
            path: "./wibble.txt".into(),
        },
        OutputFile {
            content: Content::Binary(vec![11, 6, 7]),
            path: "./wobble.bin".into(),
        },
    ])
    .expect("should create archive");

    let decoder = flate2::read::GzDecoder::new(Cursor::new(compressed_archive));
    let mut archive = tar::Archive::new(decoder);

    for entry in archive.entries().expect("archive entries") {
        let entry = entry.expect("archive entry");
        let mode = entry.header().mode().expect("entry mode");
        let entry_path = entry.path().expect("entry path");
        let path_str = entry_path.to_str().expect("path string");
        assert_eq!(mode, 0o600, "entry {path_str} has unexpected mode")
    }
}

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