command/import: Fix allow-missing-config option

We previously intentionally removed support for the allow-missing-config
option to terraform import, requiring that all imported resources have
matching config. See #24412.

However, the option was not removed from the import command, and it is
widely used. This commit reintroduces support for importing with a
missing configuration by falling back to implying the provider FQN based
on the resource type.

command/import_test.go

@@ -601,7 +601,7 @@ func TestImport_providerConfigWithVarFile(t *testing.T) {
 	testStateOutput(t, statePath, testImportStr)
 }
 
-func TestImport_disallowMissingResourceConfig(t *testing.T) {
+func TestImport_allowMissingResourceConfig(t *testing.T) {
 	defer testChdir(t, testFixturePath("import-missing-resource-config"))()
 
 	statePath := testTempFile(t)
@@ -643,15 +643,15 @@ func TestImport_disallowMissingResourceConfig(t *testing.T) {
 		"bar",
 	}
 
-	if code := c.Run(args); code != 1 {
-		t.Fatalf("import succeeded; expected failure")
+	if code := c.Run(args); code != 0 {
+		t.Fatalf("bad: %d\n\n%s", code, ui.ErrorWriter.String())
 	}
 
-	msg := ui.ErrorWriter.String()
-
-	if want := `Error: Resource test_instance.foo not found in the configuration.`; !strings.Contains(msg, want) {
-		t.Errorf("incorrect message\nwant substring: %s\ngot:\n%s", want, msg)
+	if !p.ImportResourceStateCalled {
+		t.Fatal("ImportResourceState should be called")
 	}
+
+	testStateOutput(t, statePath, testImportStr)
 }
 
 func TestImport_emptyConfig(t *testing.T) {

terraform/context_import_test.go

@@ -49,40 +49,6 @@ func TestContextImport_basic(t *testing.T) {
 	}
 }
 
-// Importing a resource which does not exist in the configuration results in an error
-func TestContextImport_basic_errpr(t *testing.T) {
-	p := testProvider("aws")
-	m := testModule(t, "import-provider")
-	ctx := testContext2(t, &ContextOpts{
-		Config: m,
-		Providers: map[addrs.Provider]providers.Factory{
-			addrs.NewDefaultProvider("aws"): testProviderFuncFixed(p),
-		},
-	})
-
-	p.ImportStateReturn = []*InstanceState{
-		&InstanceState{
-			ID:        "foo",
-			Ephemeral: EphemeralState{Type: "aws_instance"},
-		},
-	}
-
-	_, diags := ctx.Import(&ImportOpts{
-		Targets: []*ImportTarget{
-			&ImportTarget{
-				Addr: addrs.RootModuleInstance.ResourceInstance(
-					addrs.ManagedResourceMode, "aws_instance", "test", addrs.NoKey,
-				),
-				ID: "bar",
-			},
-		},
-	})
-
-	if !diags.HasErrors() {
-		t.Fatal("should error")
-	}
-}
-
 func TestContextImport_countIndex(t *testing.T) {
 	p := testProvider("aws")
 	m := testModule(t, "import-provider")

terraform/transform_import_state.go

@@ -30,29 +30,25 @@ func (t *ImportStateTransformer) Transform(g *Graph) error {
 			return fmt.Errorf("Module %s not found.", target.Addr.Module.Module())
 		}
 
-		// Get the resource config
-		rsCfg := modCfg.Module.ResourceByAddr(target.Addr.Resource.Resource)
-		if rsCfg == nil {
-			return fmt.Errorf("Resource %s not found in the configuration.", target.Addr)
-		}
-
-		// Get the provider FQN for the resource from the resource configuration
-		providerFqn := rsCfg.Provider
-
-		// This is only likely to happen in misconfigured tests.
-		if rsCfg == nil {
-			return fmt.Errorf("provider for resource %s not found in the configuration.", target.Addr)
-		}
-
-		// Get the provider local config for the resource
-		localpCfg := rsCfg.ProviderConfigAddr()
-
 		providerAddr := addrs.AbsProviderConfig{
-			Provider: providerFqn,
-			Alias:    localpCfg.Alias,
 			Module: target.Addr.Module.Module(),
 		}
 
+		// Try to find the resource config
+		rsCfg := modCfg.Module.ResourceByAddr(target.Addr.Resource.Resource)
+		if rsCfg != nil {
+			// Get the provider FQN for the resource from the resource configuration
+			providerAddr.Provider = rsCfg.Provider
+
+			// Get the alias from the resource's provider local config
+			providerAddr.Alias = rsCfg.ProviderConfigAddr().Alias
+		} else {
+			// Resource has no matching config, so use an implied provider
+			// based on the resource type
+			rsProviderType := target.Addr.Resource.Resource.ImpliedProvider()
+			providerAddr.Provider = modCfg.Module.ImpliedProviderForUnqualifiedType(rsProviderType)
+		}
+
 		node := &graphNodeImportState{
 			Addr:         target.Addr,
 			ID:           target.ID,