What causes "index.json contains no versions" in hashicorp/packer?

Verify the plugin actually has published versions on the registry/releases host.

index.json contains no versions

Error message

index.json contains no versions

What it means

After successfully unmarshaling index.json, parseIndex requires at least one entry under `versions`. An empty or versions-less object means the remote (or cached) index advertises no plugin versions at all, so there is nothing to resolve releases from.

Source

Thrown at packer/plugin-getter/remote/getter.go:82

// pluginIndex is the validated form of a plugin's index.json. Versions are
// keyed by their canonical core string (e.g. "1.1.4"); all other index
// content is ignored.
type pluginIndex struct {
	pluginType string
	versions   map[string]struct{}
}

// parseIndex validates raw index.json content into a pluginIndex.
func parseIndex(data []byte, pluginType string) (*pluginIndex, error) {
	var raw struct {
		Versions map[string]struct{} `json:"versions"`
	}
	if err := json.Unmarshal(data, &raw); err != nil {
		return nil, fmt.Errorf("malformed index.json: %w", err)
	}
	if len(raw.Versions) == 0 {
		return nil, fmt.Errorf("index.json contains no versions")
	}

	idx := &pluginIndex{
		pluginType: pluginType,
		versions:   map[string]struct{}{},
	}
	for k := range raw.Versions {
		ver, err := goversion.NewVersion(k)
		if err != nil {
			log.Printf("[WARN] remote-getter: ignoring unparseable version %q in index.json", k)
			continue
		}
		idx.versions[ver.String()] = struct{}{}
	}
	if len(idx.versions) == 0 {
		return nil, fmt.Errorf("index.json contains no usable versions")
	}
	return idx, nil

View on GitHub (pinned to eb36e3c3e4)

Solutions

Verify the plugin actually has published versions on the registry/releases host.
Check you are querying the correct plugin type/organization (typos route to an empty index).
Re-fetch or regenerate index.json if a custom mirror served an empty file.

Example fix

// before
{"versions": {}}
// after
{"versions": {"1.1.1": {}}}

Defensive patterns

Strategy: validation

Validate before calling

var idx struct{ Versions map[string]json.RawMessage `json:"versions"` }
if json.Unmarshal(body, &idx) == nil && len(idx.Versions) == 0 {
    return errors.New("plugin has no published versions; check registry")
}

Try / catch

if _, err := g.Get("releases", opts); err != nil && strings.Contains(err.Error(), "contains no versions") {
    // verify plugin address and that releases exist upstream
}

Prevention

Confirm a plugin has published releases before adding it to required_plugins.
Double-check org/repo spelling in the plugin source address.
Keep custom registry mirrors in sync with upstream releases.

When it happens

Trigger: parseIndex receives valid JSON like {} or {"versions": {}}; loadIndex then returns this error to callers such as Get("releases") and versionURL.

Common situations: A newly created plugin on the registry with no published releases yet; an index.json truncated/regenerated without versions; pointing a custom plugin registry mirror at an empty bucket.

Related errors

AI-assisted analysis of hashicorp/packer@eb36e3c3e4 (2026-09-05). Data as JSON: /api/errors/54bafa23c9f6ce89. Report an issue: GitHub.