don't add missing provider aliases to the graph

A missing provider alias should not be implicitly added to the graph.

Run the AttachaProviderConfigTransformer immediately after adding the
providers, since the ProviderConfigTransformer should have just added
these nodes.

terraform/context_import_test.go

@@ -725,7 +725,8 @@ func TestContextImport_multiStateSame(t *testing.T) {
 	}
 }
 
-func TestContextImport_customProvider(t *testing.T) {
+// import missing a provider alias should fail
+func TestContextImport_customProviderMissing(t *testing.T) {
 	p := testProvider("aws")
 	m := testModule(t, "import-provider")
 	ctx := testContext2(t, &ContextOpts{
@@ -744,6 +745,39 @@ func TestContextImport_customProvider(t *testing.T) {
 		},
 	}
 
+	_, err := ctx.Import(&ImportOpts{
+		Targets: []*ImportTarget{
+			&ImportTarget{
+				Addr:     "aws_instance.foo",
+				ID:       "bar",
+				Provider: "aws.alias",
+			},
+		},
+	})
+	if err == nil {
+		t.Fatal("expected error")
+	}
+}
+
+func TestContextImport_customProvider(t *testing.T) {
+	p := testProvider("aws")
+	m := testModule(t, "import-provider-alias")
+	ctx := testContext2(t, &ContextOpts{
+		Module: m,
+		ProviderResolver: ResourceProviderResolverFixed(
+			map[string]ResourceProviderFactory{
+				"aws": testProviderFuncFixed(p),
+			},
+		),
+	})
+
+	p.ImportStateReturn = []*InstanceState{
+		&InstanceState{
+			ID:        "foo",
+			Ephemeral: EphemeralState{Type: "aws_instance"},
+		},
+	}
+
 	state, err := ctx.Import(&ImportOpts{
 		Targets: []*ImportTarget{
 			&ImportTarget{

terraform/test-fixtures/import-provider-alias/main.tf

@@ -0,0 +1,4 @@
+provider "aws" {
+  foo = "bar"
+  alias = "alias"
+}

terraform/transform_provider.go

@@ -19,6 +19,10 @@ func TransformProviders(providers []string, concrete ConcreteProviderNodeFunc, m
 			Providers: providers,
 			Concrete:  concrete,
 		},
+		// Attach configuration to each provider instance
+		&AttachProviderConfigTransformer{
+			Module: mod,
+		},
 		// Add any remaining missing providers
 		&MissingProviderTransformer{
 			Providers: providers,
@@ -30,10 +34,6 @@ func TransformProviders(providers []string, concrete ConcreteProviderNodeFunc, m
 		&DisableProviderTransformer{},
 		// Connect provider to their parent provider nodes
 		&ParentProviderTransformer{},
-		// Attach configuration to each provider instance
-		&AttachProviderConfigTransformer{
-			Module: mod,
-		},
 	)
 }
 
@@ -109,6 +109,7 @@ func (t *ProviderTransformer) Transform(g *Graph) error {
 				break
 			}
 
+			log.Printf("[DEBUG] resource %s using provider %s", dag.VertexName(pv), key)
 			pv.SetProvider(key)
 			g.Connect(dag.BasicEdge(v, target))
 		}
@@ -196,6 +197,12 @@ func (t *MissingProviderTransformer) Transform(g *Graph) error {
 			continue
 		}
 
+		// we don't implicitly create aliased providers
+		if strings.Contains(p, ".") {
+			log.Println("[DEBUG] not adding missing provider alias", p)
+			continue
+		}
+
 		// create the misisng top-level provider
 		provider = t.Concrete(&NodeAbstractProvider{
 			NameValue: p,