fix: destroy with no bundling

docs/code-deployment-flow.md

@@ -14,6 +14,24 @@ Deep dive into `Nextjs` constructs code deployment flow - how your Next.js code
 _Only applicable for PNPM Monorepos_
 PNPM Monorepos use symlinks between workspace node_modules and the top level node_modules. CDK Assets do not support symlinks despite the configuration options available. Therefore, we must zip up the assets ourselves. Also, `nextjs-bucket-deployment.ts` handles symlinks to unzip and zip symlinks within Lambda Custom Resources (for ServerFnBucketDeployment).
 
+
+## Conditional Build Logic
+
+`NextjjsBuild` will use the following logic to determine if a build is required or not to proceed.
+
+```
+| bundlingRequired | skipBuild | Scenario                        | Action                                            |
+|------------------|-----------|---------------------------------|---------------------------------------------------|
+| true             | true      | deploy/synth with reused bundle | no build, check .open-next exists, fail if not    |
+| true             | false     | regular deploy/synth            | build, .open-next will exist                      |
+| false            | false     | destroy                         | no build, check if .open-next exists, if not mock |
+| false            | true      | destroy with reused bundle      | no build, check if .open-next exists, if not mock |
+```
+
+*bundlingRequired* = `Stack.of(this).bundlingRequired` [see](https://docs.aws.amazon.com/cdk/api/v2/docs/aws-cdk-lib.Stack.html#bundlingrequired)
+*skipBuild* = `NextjsProps.skipBuild`
+
+
 Relevant GitHub Issues:
 - https://github.com/aws/aws-cdk/issues/9251
 - https://github.com/Stuk/jszip/issues/386#issuecomment-634773343

src/NextjsBuild.ts

@@ -5,12 +5,12 @@ import { Stack, Token } from 'aws-cdk-lib';
 import { Construct } from 'constructs';
 import {
   NEXTJS_BUILD_DIR,
+  NEXTJS_BUILD_DYNAMODB_PROVIDER_FN_DIR,
   NEXTJS_BUILD_IMAGE_FN_DIR,
   NEXTJS_BUILD_REVALIDATE_FN_DIR,
   NEXTJS_BUILD_SERVER_FN_DIR,
-  NEXTJS_STATIC_DIR,
   NEXTJS_CACHE_DIR,
-  NEXTJS_BUILD_DYNAMODB_PROVIDER_FN_DIR,
+  NEXTJS_STATIC_DIR,
 } from './constants';
 import type { NextjsProps } from './Nextjs';
 import { NextjsBucketDeployment } from './NextjsBucketDeployment';
@@ -103,9 +103,21 @@ export class NextjsBuild extends Construct {
     super(scope, id);
     this.props = props;
     this.validatePaths();
-    // when `cdk deploy "NonNextjsStack" --exclusively` is run, don't run build
-    if (Stack.of(this).bundlingRequired && !this.props.skipBuild) {
-      this.build();
+
+    const bundlingRequired = Stack.of(this).bundlingRequired;
+    const skipBuild = this.props.skipBuild;
+
+    // for more info see docs/code-deployment-flow.md Conditional Build Logic section
+    if (bundlingRequired) {
+      // deploy/synth
+      if (skipBuild) {
+        this.assertBuildDirExists(true);
+      } else {
+        this.build();
+      }
+    } else {
+      // destroy
+      this.mockNextBuildDir();
     }
   }
 
@@ -171,6 +183,17 @@ export class NextjsBuild extends Construct {
     return listDirectory(this.nextStaticDir).map((file) => path.join('/', path.relative(this.nextStaticDir, file)));
   }
 
+  private assertBuildDirExists(throwIfMissing = true) {
+    const dir = this.getNextBuildDir();
+    if (!fs.existsSync(dir)) {
+      if (throwIfMissing) {
+        throw new Error(`Build directory "${dir}" does not exist. Try removing skipBuild: true option.`);
+      }
+      return false;
+    }
+    return true;
+  }
+
   private getNextBuildDir(): string {
     const dir = path.resolve(this.props.nextjsPath, NEXTJS_BUILD_DIR);
     this.warnIfMissing(dir);
@@ -182,4 +205,23 @@ export class NextjsBuild extends Construct {
       console.warn(`Warning: ${dir} does not exist.`);
     }
   }
+
+  private mockNextBuildDir() {
+    function createMockDirAndFile(dir: string) {
+      fs.mkdirSync(dir, { recursive: true });
+      fs.writeFileSync(path.join(dir, 'package.json'), '{}', 'utf8');
+    }
+
+    const buildDirExists = this.assertBuildDirExists(false);
+    if (!buildDirExists) {
+      // mock .open-next
+      createMockDirAndFile(this.getNextBuildDir());
+      createMockDirAndFile(this.nextServerFnDir);
+      createMockDirAndFile(this.nextImageFnDir);
+      createMockDirAndFile(this.nextRevalidateFnDir);
+      createMockDirAndFile(this.nextRevalidateDynamoDBProviderFnDir);
+      createMockDirAndFile(this.nextStaticDir);
+      createMockDirAndFile(this.nextCacheDir);
+    }
+  }
 }