hashicorp/packer · error

Error building powershell wrapper: %w

Error message

Error building powershell wrapper: %w

What it means

After assembling context data (Vars, Payload, DebugMode, generated data), extractInlineScript renders the wrapPowershellString template with interpolate.Render. If template rendering fails (bad interpolation syntax, missing/invalid variable types, invalid functions), it throws "Error building powershell wrapper: %w".

Source

Thrown at provisioner/powershell/provisioner.go:330

	// we concatenate all the inline commands
	for _, command := range p.config.Inline {
		log.Printf("Found command: %s", command)
		if _, err := commandBuilder.WriteString(command + "\n\t"); err != nil {
			return "", fmt.Errorf("failed to wrap script contents: %w", err)
		}
	}

	// injecting all the variables in the string
	ctxData := p.generatedData
	ctxData["Vars"] = p.createFlattenedEnvVars(p.config.ElevatedUser != "")
	ctxData["Payload"] = commandBuilder.String()
	ctxData["DebugMode"] = p.config.DebugMode
	p.config.ctx.Data = ctxData

	data, err := interpolate.Render(wrapPowershellString, &p.config.ctx)
	if err != nil {
		return "", fmt.Errorf("Error building powershell wrapper: %w", err)
	}

	log.Printf("Writing PowerShell script to file: %s", temp.Name())
	if _, err := temp.WriteString(data); err != nil {
		return "", fmt.Errorf("Error writing PowerShell script: %w", err)
	}

	return temp.Name(), nil
}

func (p *Provisioner) Provision(ctx context.Context, ui packersdk.Ui, comm packersdk.Communicator, generatedData map[string]interface{}) error {
	ui.Say("Provisioning with Powershell...")
	p.communicator = comm
	p.generatedData = generatedData

	scripts := make([]string, len(p.config.Scripts))
	copy(scripts, p.config.Scripts)

View on GitHub (pinned to eb36e3c3e4)

Solutions

1. Inspect the wrapped cause and fix the interpolation expression in the inline script.
2. Escape literal Go-template delimiters in PowerShell (use {{`{{`}} or avoid `{{` sequences in scripts).
3. Update references to generated data keys to match your Packer version's documented set.
4. Test the inline script with a minimal template to isolate the failing expression.

Example fix

// before (inline command with literal braces)
"Write-Output "{{ "it" }}""
// after (escape braces or remove template syntax)
"Write-Output '{{ it }}'"

// Before adding inline commands, scan for suspicious Go-template syntax
for _, c := range cfg.Inline {
    if strings.Contains(c, "{{") && !strings.Contains(c, "{{ `") {
        log.Printf("inline command uses interpolation: %q — verify referenced keys exist", c)
    }
}

// Go
err := prov.Provision(ctx, ui, comm, genData)
if err != nil {
    var re *interpolate.RenderError // or inspect wrapped cause
    if strings.Contains(err.Error(), "Error building powershell wrapper") {
        fmt.Fprintf(os.Stderr, "template interpolation failed: %v\n", err)
        // fix inline template expression or escape {{ }} and retry
    }
    return err
}

When it happens

Trigger: extractInlineScript called from Provision when the Go text/template wrapPowershellString fails against the ctx data — e.g. a generated-data key used in an incompatible way or an interpolation function error.

Common situations: Using template variables in inline scripts that reference generated data unavailable at render time; a malformed {{ }} expression inside an inline command; version changes to generated data keys (e.g. build-specific variables).

Related errors

• failed to wrap script contents: %w
• Error processing command: %s
• Only one of script or scripts can be specified.
• Must supply an 'elevated_user' if 'elevated_password' provid
• Either a script file or inline script must be specified.

AI-assisted analysis of hashicorp/packer@eb36e3c3e4 (2026-09-05). Data as JSON: /api/errors/19b22cd69a785d26. Report an issue: GitHub.