terraform: GraphNodeProxy

This commit is contained in:
Mitchell Hashimoto 2015-05-01 11:38:36 -07:00
parent a0d9bc0f19
commit f24a1533f2
2 changed files with 107 additions and 0 deletions

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package terraform
import (
"github.com/hashicorp/terraform/dag"
)
// GraphNodeProxy must be implemented by nodes that are proxies.
//
// A node that is a proxy says that anything that depends on this
// node (the proxy), should also copy all the things that the proxy
// itself depends on. Example:
//
// A => proxy => C
//
// Should transform into (two edges):
//
// A => proxy => C
// A => C
//
// The purpose for this is because some transforms only look at direct
// edge connections and the proxy generally isn't meaningful in those
// situations, so we should complete all the edges.
type GraphNodeProxy interface {
Proxy() bool
}
// ProxyTransformer is a transformer that goes through the graph, finds
// vertices that are marked as proxies, and connects through their
// dependents. See above for what a proxy is.
type ProxyTransformer struct{}
func (t *ProxyTransformer) Transform(g *Graph) error {
for _, v := range g.Vertices() {
pn, ok := v.(GraphNodeProxy)
if !ok {
continue
}
// If we don't want to be proxies, don't do it
if !pn.Proxy() {
continue
}
// Connect all the things that depend on this to things that
// we depend on as the proxy. See docs for GraphNodeProxy for
// a visual explanation.
for _, s := range g.UpEdges(v).List() {
for _, t := range g.DownEdges(v).List() {
g.Connect(dag.BasicEdge(s, t))
}
}
}
return nil
}

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package terraform
import (
"strings"
"testing"
"github.com/hashicorp/terraform/dag"
)
func TestProxyTransformer(t *testing.T) {
var g Graph
proxy := &testNodeProxy{NameValue: "proxy"}
g.Add("A")
g.Add("C")
g.Add(proxy)
g.Connect(dag.BasicEdge("A", proxy))
g.Connect(dag.BasicEdge(proxy, "C"))
{
tf := &ProxyTransformer{}
if err := tf.Transform(&g); err != nil {
t.Fatalf("err: %s", err)
}
}
actual := strings.TrimSpace(g.String())
expected := strings.TrimSpace(testProxyTransformStr)
if actual != expected {
t.Fatalf("bad: %s", actual)
}
}
type testNodeProxy struct {
NameValue string
}
func (n *testNodeProxy) Name() string {
return n.NameValue
}
func (n *testNodeProxy) Proxy() bool {
return true
}
const testProxyTransformStr = `
A
C
proxy
C
proxy
C
`