fix(lib): restrict ephemeral resource lifecycle to pre/postconditions

Terraform ephemeral blocks support only precondition/postcondition in
lifecycle — createBeforeDestroy, preventDestroy, ignoreChanges and
replaceTriggeredBy are state-oriented concepts that do not apply to
stateless ephemeral resources. New TerraformEphemeralResourceLifecycle
replaces the full TerraformResourceLifecycle on the ephemeral API;
narrowing later would be jsii-breaking, so it lands before first
release.

Found in draft-PR verification (#296 review notes).

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

Author: so0k

packages/cdktn/src/terraform-ephemeral-resource.ts

@@ -6,9 +6,9 @@ import { TerraformElement } from "./terraform-element";
 import { TerraformProvider } from "./terraform-provider";
 import {
   TerraformProviderGeneratorMetadata,
-  TerraformResourceLifecycle,
   lifecycleToTerraform,
 } from "./terraform-resource";
+import { Precondition, Postcondition } from "./terraform-conditions";
 import {
   keysToSnakeCase,
   deepMerge,
@@ -40,6 +40,18 @@ const EPHEMERAL_RESOURCES_HINT = `Ephemeral resources are available in ${Object.
   .map(([product, range]) => `${product} ${range}`)
   .join(" and ")}.`;
 
+/**
+ * Lifecycle options supported by Terraform ephemeral blocks. Unlike managed
+ * resources, ephemeral resources have no state, so Terraform only supports
+ * `precondition`/`postcondition` here - `createBeforeDestroy`,
+ * `preventDestroy`, `ignoreChanges`, and `replaceTriggeredBy` are all
+ * state-oriented concepts that do not apply.
+ */
+export interface TerraformEphemeralResourceLifecycle {
+  readonly precondition?: Precondition[];
+  readonly postcondition?: Postcondition[];
+}
+
 export interface ITerraformEphemeralResource {
   readonly terraformResourceType: string;
   readonly fqn: string;
@@ -48,7 +60,7 @@ export interface ITerraformEphemeralResource {
   dependsOn?: string[];
   count?: number | TerraformCount;
   provider?: TerraformProvider;
-  lifecycle?: TerraformResourceLifecycle;
+  lifecycle?: TerraformEphemeralResourceLifecycle;
   forEach?: ITerraformIterator;
 
   interpolationForAttribute(terraformAttribute: string): IResolvable;
@@ -62,7 +74,7 @@ export interface TerraformEphemeralMetaArguments {
   readonly dependsOn?: ITerraformDependable[];
   readonly count?: number | TerraformCount;
   readonly provider?: TerraformProvider;
-  readonly lifecycle?: TerraformResourceLifecycle;
+  readonly lifecycle?: TerraformEphemeralResourceLifecycle;
   readonly forEach?: ITerraformIterator;
 }
 
@@ -87,7 +99,7 @@ export class TerraformEphemeralResource
   public dependsOn?: string[];
   public count?: number | TerraformCount;
   public provider?: TerraformProvider;
-  public lifecycle?: TerraformResourceLifecycle;
+  public lifecycle?: TerraformEphemeralResourceLifecycle;
   public forEach?: ITerraformIterator;
 
   constructor(

packages/cdktn/test/terraform-ephemeral-resource.test.ts

@@ -95,6 +95,56 @@ test("renders an ephemeral HCL block", () => {
   `);
 });
 
+test("renders a precondition lifecycle block", () => {
+  const app = Testing.app();
+  const stack = new TerraformStack(app, "test");
+  new TestProvider(stack, "provider", {});
+
+  new TestEphemeralResource(stack, "test", {
+    name: "foo",
+    lifecycle: {
+      precondition: [
+        {
+          condition: '${var.foo != ""}',
+          errorMessage: "foo must not be empty",
+        },
+      ],
+    },
+  });
+
+  expect(Testing.synth(stack)).toMatchInlineSnapshot(`
+    "{
+      "ephemeral": {
+        "test_ephemeral": {
+          "test": {
+            "lifecycle": {
+              "precondition": [
+                {
+                  "condition": "\${var.foo != \\"\\"}",
+                  "error_message": "foo must not be empty"
+                }
+              ]
+            },
+            "name": "foo"
+          }
+        }
+      },
+      "provider": {
+        "test": [
+          {}
+        ]
+      },
+      "terraform": {
+        "required_providers": {
+          "test": {
+            "version": "~> 2.0"
+          }
+        }
+      }
+    }"
+  `);
+});
+
 test("interpolationForAttribute produces ephemeral.-prefixed references", () => {
   const app = Testing.app();
   const stack = new TerraformStack(app, "test");