core: Fix MissingProviderTransformer matching existing providers

In the change to using addrs types rather than string keys directly here
I incorrectly made this use the _relative_ provider config instead of
the absolute one, causing MissingProviderTransformer to only match
providers defined in the root module (due to ambiguity in the string
representations of these address types).

The rest of this change is improved logging and test output that helped
with debugging this issue.

terraform/transform_provider.go

@@ -81,6 +81,11 @@ func (t *ProviderTransformer) Transform(g *Graph) error {
 	for _, v := range g.Vertices() {
 		if pv, ok := v.(GraphNodeProviderConsumer); ok {
 			p, exact := pv.ProvidedBy()
+			if exact {
+				log.Printf("[TRACE] ProviderTransformer: %s is provided by %s exactly", dag.VertexName(v), p)
+			} else {
+				log.Printf("[TRACE] ProviderTransformer: %s is provided by %s or inherited equivalent", dag.VertexName(v), p)
+			}
 
 			key := p.String()
 			target := m[key]
@@ -92,15 +97,21 @@ func (t *ProviderTransformer) Transform(g *Graph) error {
 				break
 			}
 
+			if target != nil {
+				log.Printf("[TRACE] ProviderTransformer: exact match for %s providing %s", p, dag.VertexName(v))
+			}
+
 			// if we don't have a provider at this level, walk up the path looking for one,
 			// unless we were told to be exact.
-			if !exact {
+			if target == nil && !exact {
 				for pp, ok := p.Inherited(); ok; pp, ok = pp.Inherited() {
 					key := pp.String()
 					target = m[key]
 					if target != nil {
+						log.Printf("[TRACE] ProviderTransformer: %s uses inherited configuration %s", dag.VertexName(v), pp)
 						break
 					}
+					log.Printf("[TRACE] ProviderTransformer: looking for %s to provide %s", pp, dag.VertexName(v))
 				}
 			}
 
@@ -119,7 +130,7 @@ func (t *ProviderTransformer) Transform(g *Graph) error {
 				key = target.(GraphNodeProvider).ProviderAddr().String()
 			}
 
-			log.Printf("[DEBUG] %s handled by %s", dag.VertexName(pv), key)
+			log.Printf("[DEBUG] %s provided by %s", dag.VertexName(pv), key)
 			pv.SetProvider(target.ProviderAddr())
 			g.Connect(dag.BasicEdge(v, target))
 		}
@@ -199,8 +210,7 @@ func (t *MissingProviderTransformer) Transform(g *Graph) error {
 		}
 
 		p, _ := pv.ProvidedBy()
-		configAddr := p.ProviderConfig
+		key := p.String()
-		key := configAddr.String()
 		provider := m[key]
 
 		// we already have it
@@ -209,7 +219,7 @@ func (t *MissingProviderTransformer) Transform(g *Graph) error {
 		}
 
 		// we don't implicitly create aliased providers
-		if configAddr.Alias != "" {
+		if p.ProviderConfig.Alias != "" {
 			log.Println("[DEBUG] not adding implicit aliased config for", p.String())
 			continue
 		}
@@ -380,6 +390,10 @@ type graphNodeProxyProvider struct {
 	target GraphNodeProvider
 }
 
+var (
+	_ GraphNodeProvider = (*graphNodeProxyProvider)(nil)
+)
+
 func (n *graphNodeProxyProvider) ProviderAddr() addrs.AbsProviderConfig {
 	return n.addr
 }
@@ -389,7 +403,7 @@ func (n *graphNodeProxyProvider) Path() addrs.ModuleInstance {
 }
 
 func (n *graphNodeProxyProvider) Name() string {
-	return n.addr.String()
+	return n.addr.String() + " (proxy)"
 }
 
 // find the concrete provider instance

terraform/transform_provider_test.go

@@ -583,7 +583,7 @@ func TestProviderConfigTransformer_implicitModule(t *testing.T) {
   provider.aws.foo
 provider.aws.foo`)
 	if actual != expected {
-		t.Fatalf("expected:\n%s\n\ngot:\n%s", expected, actual)
+		t.Fatalf("wrong result\n\nexpected:\n%s\n\ngot:\n%s", expected, actual)
 	}
 }