terraform/terraform/transform_diff.go

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package terraform
import (
"fmt"
"log"
"github.com/hashicorp/terraform/config/module"
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"github.com/hashicorp/terraform/dag"
)
// DiffTransformer is a GraphTransformer that adds the elements of
// the diff to the graph.
//
// This transform is used for example by the ApplyGraphBuilder to ensure
// that only resources that are being modified are represented in the graph.
//
// Module and State is still required for the DiffTransformer for annotations
// since the Diff doesn't contain all the information required to build the
// complete graph (such as create-before-destroy information). The graph
// is built based on the diff first, though, ensuring that only resources
// that are being modified are present in the graph.
type DiffTransformer struct {
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Concrete ConcreteResourceNodeFunc
Diff *Diff
Module *module.Tree
State *State
}
func (t *DiffTransformer) Transform(g *Graph) error {
// If the diff is nil or empty (nil is empty) then do nothing
if t.Diff.Empty() {
return nil
}
// Go through all the modules in the diff.
log.Printf("[TRACE] DiffTransformer: starting")
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var nodes []dag.Vertex
for _, m := range t.Diff.Modules {
log.Printf("[TRACE] DiffTransformer: Module: %s", m)
// TODO: If this is a destroy diff then add a module destroy node
// Go through all the resources in this module.
for name, inst := range m.Resources {
log.Printf("[TRACE] DiffTransformer: Resource %q: %#v", name, inst)
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// We have changes! This is a create or update operation.
// First grab the address so we have a unique way to
// reference this resource.
addr, err := parseResourceAddressInternal(name)
if err != nil {
panic(fmt.Sprintf(
"Error parsing internal name, this is a bug: %q", name))
}
// Very important: add the module path for this resource to
// the address. Remove "root" from it.
addr.Path = m.Path[1:]
// If we're destroying, add the destroy node
if inst.Destroy || inst.GetDestroyDeposed() {
abstract := &NodeAbstractResource{Addr: addr}
g.Add(&NodeDestroyResource{NodeAbstractResource: abstract})
}
// If we have changes, then add the applyable version
if len(inst.Attributes) > 0 {
// Add the resource to the graph
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abstract := &NodeAbstractResource{Addr: addr}
var node dag.Vertex = abstract
if f := t.Concrete; f != nil {
node = f(abstract)
}
nodes = append(nodes, node)
}
}
}
// Add all the nodes to the graph
for _, n := range nodes {
g.Add(n)
}
return nil
}