1package hcl
2
3// ExprList tests if the given expression is a static list construct and,
4// if so, extracts the expressions that represent the list elements.
5// If the given expression is not a static list, error diagnostics are
6// returned.
7//
8// A particular Expression implementation can support this function by
9// offering a method called ExprList that takes no arguments and returns
10// []Expression. This method should return nil if a static list cannot
11// be extracted.  Alternatively, an implementation can support
12// UnwrapExpression to delegate handling of this function to a wrapped
13// Expression object.
14func ExprList(expr Expression) ([]Expression, Diagnostics) {
15	type exprList interface {
16		ExprList() []Expression
17	}
18
19	physExpr := UnwrapExpressionUntil(expr, func(expr Expression) bool {
20		_, supported := expr.(exprList)
21		return supported
22	})
23
24	if exL, supported := physExpr.(exprList); supported {
25		if list := exL.ExprList(); list != nil {
26			return list, nil
27		}
28	}
29	return nil, Diagnostics{
30		&Diagnostic{
31			Severity: DiagError,
32			Summary:  "Invalid expression",
33			Detail:   "A static list expression is required.",
34			Subject:  expr.StartRange().Ptr(),
35		},
36	}
37}
38