hcl/expr_map.go

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package hcl
// ExprMap tests if the given expression is a static map construct and,
// if so, extracts the expressions that represent the map elements.
// If the given expression is not a static map, error diagnostics are
// returned.
//
// A particular Expression implementation can support this function by
// offering a method called ExprMap that takes no arguments and returns
// []KeyValuePair. This method should return nil if a static map cannot
// be extracted. Alternatively, an implementation can support
// UnwrapExpression to delegate handling of this function to a wrapped
// Expression object.
func ExprMap(expr Expression) ([]KeyValuePair, Diagnostics) {
type exprMap interface {
ExprMap() []KeyValuePair
}
physExpr := UnwrapExpressionUntil(expr, func(expr Expression) bool {
_, supported := expr.(exprMap)
return supported
})
if exM, supported := physExpr.(exprMap); supported {
if pairs := exM.ExprMap(); pairs != nil {
return pairs, nil
}
}
return nil, Diagnostics{
&Diagnostic{
Severity: DiagError,
Summary: "Invalid expression",
Detail: "A static map expression is required.",
Subject: expr.StartRange().Ptr(),
},
}
}
// KeyValuePair represents a pair of expressions that serve as a single item
// within a map or object definition construct.
type KeyValuePair struct {
Key Expression
Value Expression
}