Do not error on _set_perms(path) on Wasm32

[fschutt]

Since Wasm32 does not yet have support for file permissions it is better to silently ignore them rather than to fail, since the rest of the library can still work on wasm32.

[alexcrichton]

I think there's already configuration to ignore setting permissions, so I think it might be better to enable that instead of silently ignoring file permissions?

[fschutt]

It errors even if using set_preserve_permissions(false). I just found this issue because file.unpack() triggers this case on wasm32-wasi:

type UnpackedFiles = BTreeMap<DirOrFile, Vec<u8>>;

/// Unzips a .tar.gz file, returning the [FileName => FileContents]
pub fn unpack_tar_gz(bytes: Vec<u8>) -> Result<UnpackedFiles, ConvertError> {
    use flate2::read::GzDecoder;
    use std::io::{Cursor, Read};
    use tar::{Archive, EntryType, Unpacked};

    let mut cursor = Cursor::new(bytes);
    let mut archive = Archive::new(GzDecoder::new(cursor));

    // mtime is not implemented on WASM
    #[cfg(target_arch = "wasm32")] {
        archive.set_preserve_mtime(false);
        archive.set_preserve_permissions(false);
    }

    // TODO(felix): it would be ideal if the .tar.gz file could
    // be unpacked in-memory instead of requiring disk access.

    // Use a random directory name for unpacking: in case the
    // tool is ran in parallel, this would otherwise lead to
    // file conflicts
    let rand_dir = rand::random::<u64>();
    let tempdir = webc::webc_temp_dir()
        .join("wapm-to-webc")
        .join(&format!("{rand_dir}"));

    let _ = std::fs::remove_dir(&tempdir); // no error if dir doesn't exist
    let _ = std::fs::create_dir_all(&tempdir)
        .map_err(|e| ConvertError::Io(format!("{}", tempdir.display()), e))?;

    let mut files = BTreeMap::default();

    for (i, file) in archive.entries().unwrap().enumerate() {
        let mut file = file.map_err(|e| ConvertError::Io(format!("{}", tempdir.display()), e))?;

        let file_type = file.header().entry_type();

        let path = file
            .path()
            .map_err(|e| ConvertError::Io(format!("{}", tempdir.display()), e))?
            .to_owned()
            .to_path_buf();

        let outpath = tempdir.clone().join(&format!("{i}.bin"));

        let _ = file
            .unpack(&outpath) // <------------------------------- ERROR
            .map_err(|e| ConvertError::Io(format!("{}", outpath.display()), e))?;

        let path = match file_type {
            EntryType::Regular => DirOrFile::File(path),
            EntryType::Directory => DirOrFile::Dir(path),
            e => {
                return Err(ConvertError::Other(anyhow::anyhow!(
                    "Invalid file_type for path \"{}\": {:?}",
                    path.display(),
                    e
                )));
            }
        };

        let bytes = match &path {
            DirOrFile::File(_) => std::fs::read(&outpath)
                .map_err(|e| ConvertError::Io(format!("{}", outpath.display()), e))?,
            DirOrFile::Dir(_) => Vec::new(),
        };

        files.insert(path, bytes);
    }

    nuke_dir(tempdir)?;

    Ok(files)
}

[alexcrichton]

If archive.set_preserve_permissions(false) doesn't work then I think that's the bug to fix rather than ignoring it on wasm