feat: accept onDestroy command to run before resource destruction

Accept an optional command via `onDestroy` parameter to enable running
a command during destroy-time.
See also: https://developer.hashicorp.com/terraform/language/resources/provisioners/syntax#destroy-time-provisioners

src/index.ts

@@ -42,13 +42,27 @@ export interface LocalExecConfig {
    * @default true
    */
   readonly copyBeforeRun?: boolean;
+
+  /**
+   * Command to run at destroy-time.
+   */
+  readonly onDestroy?: string;
 }
 
 export { NullProvider as Provider } from "@cdktf/provider-null/lib/provider";
 
+interface LocalExecProvisioner {
+  "local-exec": {
+    working_dir: string;
+    command: string;
+    when?: string;
+  };
+}
+
 export class LocalExec extends Resource {
   public cwd: string;
   public command: string;
+  public onDestroy?: string;
 
   constructor(scope: Construct, id: string, config: LocalExecConfig) {
     super(scope, id, config);
@@ -63,8 +77,9 @@ export class LocalExec extends Resource {
 
     this.cwd = workingDir;
     this.command = config.command;
+    this.onDestroy = config.onDestroy;
 
-    this.addOverride("provisioner", [
+    const overrides: LocalExecProvisioner[] = [
       {
         "local-exec": {
           working_dir: workingDir,
@@ -74,6 +89,21 @@ export class LocalExec extends Resource {
           }),
         },
       },
-    ]);
+    ];
+
+    if (typeof this.onDestroy === "string") {
+      overrides.push({
+        "local-exec": {
+          when: "destroy",
+          working_dir: workingDir,
+          command: Lazy.stringValue({
+            // TODO: wrap command to capture stdout and stderr
+            produce: () => this.onDestroy,
+          }),
+        },
+      });
+    }
+
+    this.addOverride("provisioner", overrides);
   }
 }

test/local-exec.test.ts

@@ -24,7 +24,13 @@ const apply = (addConstructs: (scope: Construct) => void) => {
     cwd: outdir,
   });
 
-  return outdir;
+  const destroy = () => {
+    execSync("terraform destroy -auto-approve", {
+      cwd: outdir,
+    });
+  };
+
+  return { outdir, destroy };
 };
 
 const workingDirectoryForAsset = (manifestPath: string, name: string) => {
@@ -61,7 +67,7 @@ describe("LocalExec", () => {
 
   test("runs command inside copy of working directory", () => {
     // Create a file in the stack directory
-    const outdir = apply((stack) => {
+    const { outdir } = apply((stack) => {
       new LocalExec(stack, "myresource", {
         command: `cp ${__filename} test.txt`,
         cwd: __dirname,
@@ -112,7 +118,7 @@ describe("LocalExec", () => {
 
   test("runs command can use token value inside a command", () => {
     const passwordLength = 4;
-    const outdir = apply((stack) => {
+    const { outdir } = apply((stack) => {
       new provider.RandomProvider(stack, "random");
 
       const waiter = new LocalExec(stack, "timer", {
@@ -144,7 +150,7 @@ describe("LocalExec", () => {
 
   test("command can be overwritten", () => {
     // Create a file in the stack directory
-    const outdir = apply((stack) => {
+    const { outdir } = apply((stack) => {
       const exec = new LocalExec(stack, "myresource", {
         command: "ls -la",
         cwd: __dirname,
@@ -158,4 +164,21 @@ describe("LocalExec", () => {
     expect(fs.existsSync(path.resolve(workingDir, "test.txt"))).toBe(true);
     expect(fs.existsSync(path.resolve(__dirname, "test.txt"))).toBe(false);
   });
+
+  test("can specify a command to run at destroy-time", () => {
+    // Create a file in the working directory
+    const { destroy } = apply((stack) => {
+      new LocalExec(stack, "test", {
+        command: "cp origin.txt test.txt",
+        cwd: testdir,
+        onDestroy: "rm test.txt",
+      });
+    });
+
+    expect(fs.existsSync(path.resolve(testdir, "test.txt"))).toBe(true);
+
+    destroy();
+
+    expect(fs.existsSync(path.resolve(testdir, "test.txt"))).toBe(false);
+  });
 });