vendor/github.com/hashicorp/terraform/terraform/shadow.go

   1 package terraform
   2
   3 // Shadow is the interface that any "shadow" structures must implement.
   4 //
   5 // A shadow structure is an interface implementation (typically) that
   6 // shadows a real implementation and verifies that the same behavior occurs
   7 // on both. The semantics of this behavior are up to the interface itself.
   8 //
   9 // A shadow NEVER modifies real values or state. It must always be safe to use.
  10 //
  11 // For example, a ResourceProvider shadow ensures that the same operations
  12 // are done on the same resources with the same configurations.
  13 //
  14 // The typical usage of a shadow following this interface is to complete
  15 // the real operations, then call CloseShadow which tells the shadow that
  16 // the real side is done. Then, once the shadow is also complete, call
  17 // ShadowError to find any errors that may have been caught.
  18 type Shadow interface {
  19         // CloseShadow tells the shadow that the REAL implementation is
  20         // complete. Therefore, any calls that would block should now return
  21         // immediately since no more changes will happen to the real side.
  22         CloseShadow() error
  23
  24         // ShadowError returns the errors that the shadow has found.
  25         // This should be called AFTER CloseShadow and AFTER the shadow is
  26         // known to be complete (no more calls to it).
  27         ShadowError() error
  28 }