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

   1 package terraform
   2
   3 import (
   4         "log"
   5
   6         "github.com/hashicorp/terraform/dag"
   7 )
   8
   9 // GraphNodeExapndable is an interface that nodes can implement to
  10 // signal that they can be expanded. Expanded nodes turn into
  11 // GraphNodeSubgraph nodes within the graph.
  12 type GraphNodeExpandable interface {
  13         Expand(GraphBuilder) (GraphNodeSubgraph, error)
  14 }
  15
  16 // GraphNodeDynamicExpandable is an interface that nodes can implement
  17 // to signal that they can be expanded at eval-time (hence dynamic).
  18 // These nodes are given the eval context and are expected to return
  19 // a new subgraph.
  20 type GraphNodeDynamicExpandable interface {
  21         DynamicExpand(EvalContext) (*Graph, error)
  22 }
  23
  24 // GraphNodeSubgraph is an interface a node can implement if it has
  25 // a larger subgraph that should be walked.
  26 type GraphNodeSubgraph interface {
  27         Subgraph() dag.Grapher
  28 }
  29
  30 // ExpandTransform is a transformer that does a subgraph expansion
  31 // at graph transform time (vs. at eval time). The benefit of earlier
  32 // subgraph expansion is that errors with the graph build can be detected
  33 // at an earlier stage.
  34 type ExpandTransform struct {
  35         Builder GraphBuilder
  36 }
  37
  38 func (t *ExpandTransform) Transform(v dag.Vertex) (dag.Vertex, error) {
  39         ev, ok := v.(GraphNodeExpandable)
  40         if !ok {
  41                 // This isn't an expandable vertex, so just ignore it.
  42                 return v, nil
  43         }
  44
  45         // Expand the subgraph!
  46         log.Printf("[DEBUG] vertex %q: static expanding", dag.VertexName(ev))
  47         return ev.Expand(t.Builder)
  48 }