vendor/github.com/hashicorp/hcl2/hcl/expr_map.go

   1 package hcl
   2
   3 // ExprMap tests if the given expression is a static map construct and,
   4 // if so, extracts the expressions that represent the map elements.
   5 // If the given expression is not a static map, error diagnostics are
   6 // returned.
   7 //
   8 // A particular Expression implementation can support this function by
   9 // offering a method called ExprMap that takes no arguments and returns
  10 // []KeyValuePair. This method should return nil if a static map cannot
  11 // be extracted.  Alternatively, an implementation can support
  12 // UnwrapExpression to delegate handling of this function to a wrapped
  13 // Expression object.
  14 func ExprMap(expr Expression) ([]KeyValuePair, Diagnostics) {
  15         type exprMap interface {
  16                 ExprMap() []KeyValuePair
  17         }
  18
  19         physExpr := UnwrapExpressionUntil(expr, func(expr Expression) bool {
  20                 _, supported := expr.(exprMap)
  21                 return supported
  22         })
  23
  24         if exM, supported := physExpr.(exprMap); supported {
  25                 if pairs := exM.ExprMap(); pairs != nil {
  26                         return pairs, nil
  27                 }
  28         }
  29         return nil, Diagnostics{
  30                 &Diagnostic{
  31                         Severity: DiagError,
  32                         Summary:  "Invalid expression",
  33                         Detail:   "A static map expression is required.",
  34                         Subject:  expr.StartRange().Ptr(),
  35                 },
  36         }
  37 }
  38
  39 // KeyValuePair represents a pair of expressions that serve as a single item
  40 // within a map or object definition construct.
  41 type KeyValuePair struct {
  42         Key   Expression
  43         Value Expression
  44 }