hashicorp/packer · error

transformReleasesVersionStream got nil body

Error message

transformReleasesVersionStream got nil body

What it means

transformReleasesVersionStream in packer/plugin-getter/release/getter.go requires a non-nil HTTP response body (the GitHub tags stream) to decode. If the getter hands it a nil body, it returns this error instead of panicking on a nil reader. Indicates the upstream fetch produced no response body.

Source

Thrown at packer/plugin-getter/release/getter.go:47

var _ plugingetter.Getter = &Getter{}

func transformZipStream() func(in io.ReadCloser) (io.ReadCloser, error) {
	return func(in io.ReadCloser) (io.ReadCloser, error) {
		defer in.Close()
		buf := new(bytes.Buffer)
		_, err := io.Copy(buf, in)
		if err != nil {
			panic(err)
		}
		return io.NopCloser(buf), nil
	}
}

// transformReleasesVersionStream get a stream from github tags and transforms it into
// something Packer wants, namely a json list of Release.
func transformReleasesVersionStream(in io.ReadCloser) (io.ReadCloser, error) {
	if in == nil {
		return nil, fmt.Errorf("transformReleasesVersionStream got nil body")
	}
	defer in.Close()
	dec := json.NewDecoder(in)

	var m gh.PluginMetadata
	if err := dec.Decode(&m); err != nil {
		return nil, err
	}

	var out []plugingetter.Release
	for _, m := range m.Versions {
		out = append(out, plugingetter.Release{
			Version: "v" + m.Version,
		})
	}

	buf := &bytes.Buffer{}
	if err := json.NewEncoder(buf).Encode(out); err != nil {

View on GitHub (pinned to eb36e3c3e4)

Solutions

1. Check connectivity to github.com (curl https://github.com/<org>/<repo>/tags) and fix proxy/firewall access
2. Re-run `packer init` — transient network failures can produce empty responses
3. Inspect the plugin source identifier; a wrong host/namespace can hit an endpoint with no body
4. Configure proper HTTPS_PROXY settings in restricted environments
5. If reproducible with a valid identifier, file a bug with PACKER_LOG output

Example fix

// before
$ packer init .
Error: transformReleasesVersionStream got nil body
// after (behind corporate proxy)
export HTTPS_PROXY=http://proxy.corp:3128
packer init .

// verify the release listing endpoint returns a body before init
curl -fsSL https://github.com/<org>/<plugin>/releases -o /dev/null && \
  echo "github reachable" || echo "fix proxy/network first"

// Go-side guard used by the library itself
if in == nil {
    return nil, fmt.Errorf("transformReleasesVersionStream got nil body")
}

for attempt := 0; attempt < 3; attempt++ {
    if err := run("packer", "init", "."); err == nil {
        break
    }
    time.Sleep(2 * time.Second)
}

When it happens

Trigger: The release getter passes a nil io.ReadCloser to transformReleasesVersionStream — e.g. an HTTP response with a nil Body from a failed or degenerate listing request to github.com tags.

Common situations: Network failure or blocked github.com access returning an empty/nil body; a mocked or misconfigured getter in tests; proxy returning an empty response for the plugin's tags listing during `packer init`.

Related errors

• could not find a local nor a remote checksum for plugin %q %
• could not parse release: %w
• could not write final plugin binary file: %w
• failed to checksum binary file: %s
• failed to write local binary checksum file: %s

AI-assisted analysis of hashicorp/packer@eb36e3c3e4 (2026-09-05). Data as JSON: /api/errors/856671e03077258d. Report an issue: GitHub.