What causes "expressions are not allowed here" in nektos/act?

Replace the expression with a literal value (number, float, or quoted string) at that location

expressions are not allowed here

Error message

expressions are not allowed here

What it means

Thrown by Node.checkSingleExpression in pkg/schema/schema.go when validating a ${{ }} expression inside a schema node that has an empty Context (no allowed context variables), and the expression token is not a plain literal (int, float, or string). Nodes without context (e.g. run-name fragments or keys where no github/env/vars context is permitted) may only contain constant literals.

Source

Thrown at pkg/schema/schema.go:133

	Schema     *Schema
	Context    []string
}

type FunctionInfo struct {
	name string
	min  int
	max  int
}

func (s *Node) checkSingleExpression(exprNode actionlint.ExprNode) error {
	if len(s.Context) == 0 {
		switch exprNode.Token().Kind {
		case actionlint.TokenKindInt:
		case actionlint.TokenKindFloat:
		case actionlint.TokenKindString:
			return nil
		default:
			return fmt.Errorf("expressions are not allowed here")
		}
	}

	funcs := s.GetFunctions()

	var err error
	actionlint.VisitExprNode(exprNode, func(node, _ actionlint.ExprNode, entering bool) {
		if funcCallNode, ok := node.(*actionlint.FuncCallNode); entering && ok {
			for _, v := range *funcs {
				if strings.EqualFold(funcCallNode.Callee, v.name) {
					if v.min > len(funcCallNode.Args) {
						err = errors.Join(err, fmt.Errorf("Missing parameters for %s expected >= %v got %v", funcCallNode.Callee, v.min, len(funcCallNode.Args)))
					}
					if v.max < len(funcCallNode.Args) {
						err = errors.Join(err, fmt.Errorf("Too many parameters for %s expected <= %v got %v", funcCallNode.Callee, v.max, len(funcCallNode.Args)))
					}
					return
				}

View on GitHub (pinned to 4f41128141)

Solutions

Replace the expression with a literal value (number, float, or quoted string) at that location
Move the dynamic reference into a position the schema allows context (e.g. a field with github/env context)
Check the schema JSON for the node in question and confirm which fields accept expressions

Example fix

# before (context not allowed at this node):
key: ${{ github.event_name }}
# after:
key: 'static-value'

Defensive patterns

Strategy: validation

Validate before calling

# Pre-check: at positions where no context is allowed, use only literals
# ${{ 1 }}, ${{ 1.5 }}, ${{ 'text' }} are OK; anything else will be rejected

Try / catch

Treat as fatal validation error; surface the location prefix and fix the YAML — retrying unchanged input cannot succeed.

Prevention

Consult the schema node's Context list before adding expressions
Prefer literal values in structural fields (names, keys)
Run `act` schema validation in CI for every workflow change

When it happens

Trigger: A ${{ }} expression referencing any non-literal token (variable access, function call, object access) placed in a schema position whose Context list is empty. Example: putting ${{ github.event.name }} in a location the schema defines without context variables.

Common situations: Hand-editing workflow YAML and using context references where only static values are allowed; schema definitions loaded from a JSON schema that omits the context array for that node.

Related errors

AI-assisted analysis of nektos/act@4f41128141 (2026-08-15). Data as JSON: /api/errors/6a6e0869ea88362c. Report an issue: GitHub.