deferred actions: fix support for config generation when importing an…

… unknown resource (#35319)

internal/terraform/context_apply_deferred_test.go

@@ -2621,6 +2621,36 @@ import {
 		},
 	}
 
+	unknownImportDefersConfigGeneration = deferredActionsTest{
+		configs: map[string]string{
+			"main.tf": `
+variable "id" {
+	type = string
+}
+
+import {
+	id = var.id
+	to = test.a
+}
+`,
+		},
+		stages: []deferredActionsTestStage{
+			{
+				buildOpts: func(opts *PlanOpts) {
+					opts.GenerateConfigPath = "generated.tf"
+				},
+				inputs: map[string]cty.Value{
+					"id": cty.UnknownVal(cty.String),
+				},
+				wantPlanned: make(map[string]cty.Value),
+				wantActions: make(map[string]plans.Action),
+				wantDeferred: map[string]ExpectedDeferred{
+					"test.a": {Reason: providers.DeferredReasonResourceConfigUnknown, Action: plans.NoOp},
+				},
+			},
+		},
+	}
+
 	unknownImportTo = deferredActionsTest{
 		configs: map[string]string{
 			"main.tf": `
@@ -2929,6 +2959,7 @@ func TestContextApply_deferredActions(t *testing.T) {
 		"module_deferred_for_each_value":                    moduleDeferredForEachValue,
 		"module_inner_resource_instance_deferred":           moduleInnerResourceInstanceDeferred,
 		"unknown_import_id":                                 unknownImportId,
+		"unknown_import_defers_config_generation":           unknownImportDefersConfigGeneration,
 		"unknown_import_to":                                 unknownImportTo,
 		"unknown_import_to_existing_state":                  unknownImportToExistingState,
 		"unknown_import_to_partial_existing_state":          unknownImportToPartialExistingState,

internal/terraform/node_resource_plan_instance.go

@@ -190,6 +190,37 @@ func (n *NodePlannableResourceInstance) managedResourceExecute(ctx EvalContext)
 			deferred = &providers.Deferred{
 				Reason: providers.DeferredReasonResourceConfigUnknown,
 			}
+			if n.Config == nil && len(n.generateConfigPath) > 0 {
+				// Then we're supposed to be generating configuration for this
+				// resource, but we can't because the configuration is unknown.
+				//
+				// Normally, the rest of this function would just be about
+				// planning the known configuration to make sure everything we
+				// do know about it is correct, but we can't even do that here.
+				//
+				// What we'll do is write out the address as being deferred with
+				// an entirely unknown value. Then we'll skip the rest of this
+				// function. (a) We're going to panic later when it complains
+				// about having no configuration, and (b) the rest of the
+				// function isn't doing anything as there is no configuration
+				// to validate.
+
+				impliedType := providerSchema.ResourceTypes[addr.Resource.Resource.Type].Block.ImpliedType()
+				ctx.Deferrals().ReportResourceInstanceDeferred(addr, providers.DeferredReasonResourceConfigUnknown, &plans.ResourceInstanceChange{
+					Addr:         addr,
+					PrevRunAddr:  addr,
+					ProviderAddr: n.ResolvedProvider,
+					Change: plans.Change{
+						Action: plans.NoOp, // assume we'll get the config generation correct.
+						Before: cty.NullVal(impliedType),
+						After:  cty.UnknownVal(impliedType),
+						Importing: &plans.Importing{
+							ID: n.importTarget,
+						},
+					},
+				})
+				return diags
+			}
 		}
 	} else {
 		var readDiags tfdiags.Diagnostics