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

   1 package terraform
   2
   3 import (
   4         "log"
   5         "strings"
   6 )
   7
   8 // EvalNode is the interface that must be implemented by graph nodes to
   9 // evaluate/execute.
  10 type EvalNode interface {
  11         // Eval evaluates this node with the given context. The second parameter
  12         // are the argument values. These will match in order and 1-1 with the
  13         // results of the Args() return value.
  14         Eval(EvalContext) (interface{}, error)
  15 }
  16
  17 // GraphNodeEvalable is the interface that graph nodes must implement
  18 // to enable valuation.
  19 type GraphNodeEvalable interface {
  20         EvalTree() EvalNode
  21 }
  22
  23 // EvalEarlyExitError is a special error return value that can be returned
  24 // by eval nodes that does an early exit.
  25 type EvalEarlyExitError struct{}
  26
  27 func (EvalEarlyExitError) Error() string { return "early exit" }
  28
  29 // Eval evaluates the given EvalNode with the given context, properly
  30 // evaluating all args in the correct order.
  31 func Eval(n EvalNode, ctx EvalContext) (interface{}, error) {
  32         // Call the lower level eval which doesn't understand early exit,
  33         // and if we early exit, it isn't an error.
  34         result, err := EvalRaw(n, ctx)
  35         if err != nil {
  36                 if _, ok := err.(EvalEarlyExitError); ok {
  37                         return nil, nil
  38                 }
  39         }
  40
  41         return result, err
  42 }
  43
  44 // EvalRaw is like Eval except that it returns all errors, even if they
  45 // signal something normal such as EvalEarlyExitError.
  46 func EvalRaw(n EvalNode, ctx EvalContext) (interface{}, error) {
  47         path := "unknown"
  48         if ctx != nil {
  49                 path = strings.Join(ctx.Path(), ".")
  50         }
  51
  52         log.Printf("[DEBUG] %s: eval: %T", path, n)
  53         output, err := n.Eval(ctx)
  54         if err != nil {
  55                 if _, ok := err.(EvalEarlyExitError); ok {
  56                         log.Printf("[DEBUG] %s: eval: %T, err: %s", path, n, err)
  57                 } else {
  58                         log.Printf("[ERROR] %s: eval: %T, err: %s", path, n, err)
  59                 }
  60         }
  61
  62         return output, err
  63 }