chore(cx-api): break circular dependencies

packages/@aws-cdk/cx-api/lib/artifacts/cloudformation-artifact.ts

@@ -2,7 +2,7 @@ import * as fs from 'fs';
 import * as path from 'path';
 import * as cxschema from '@aws-cdk/cloud-assembly-schema';
 import { CloudArtifact } from '../cloud-artifact';
-import { CloudAssembly } from '../cloud-assembly';
+import type { CloudAssembly } from '../cloud-assembly';
 import { Environment, EnvironmentUtils } from '../environment';
 
 export class CloudFormationStackArtifact extends CloudArtifact {

packages/@aws-cdk/cx-api/lib/artifacts/nested-cloud-assembly-artifact-aug.ts

@@ -0,0 +1,18 @@
+import { CloudAssembly } from '../cloud-assembly';
+import { NestedCloudAssemblyArtifact } from './nested-cloud-assembly-artifact';
+
+const cacheSym = Symbol();
+
+/**
+ * The nested Assembly
+ *
+ * Declared in a different file to break circular dep between CloudAssembly and NestedCloudAssemblyArtifact
+ */
+Object.defineProperty(NestedCloudAssemblyArtifact.prototype, 'nestedAssembly', {
+  get() {
+    if (!this[cacheSym]) {
+      this[cacheSym] = new CloudAssembly(this.fullPath);
+    }
+    return this[cacheSym];
+  },
+});

packages/@aws-cdk/cx-api/lib/artifacts/nested-cloud-assembly-artifact.ts

@@ -1,7 +1,7 @@
 import * as path from 'path';
 import * as cxschema from '@aws-cdk/cloud-assembly-schema';
 import { CloudArtifact } from '../cloud-artifact';
-import { CloudAssembly } from '../cloud-assembly';
+import type { CloudAssembly } from '../cloud-assembly';
 
 /**
  * Asset manifest is a description of a set of assets which need to be built and published
@@ -17,11 +17,6 @@ export class NestedCloudAssemblyArtifact extends CloudArtifact {
    */
   public readonly displayName: string;
 
-  /**
-   * Cache for the inner assembly loading
-   */
-  private _nestedAssembly?: CloudAssembly;
-
   constructor(assembly: CloudAssembly, name: string, artifact: cxschema.ArtifactManifest) {
     super(assembly, name, artifact);
 
@@ -36,14 +31,13 @@ export class NestedCloudAssemblyArtifact extends CloudArtifact {
   public get fullPath(): string {
     return path.join(this.assembly.directory, this.directoryName);
   }
+}
 
+export interface NestedCloudAssemblyArtifact {
   /**
    * The nested Assembly
    */
-  public get nestedAssembly(): CloudAssembly {
-    if (!this._nestedAssembly) {
-      this._nestedAssembly = new CloudAssembly(this.fullPath);
-    }
-    return this._nestedAssembly;
-  }
-}
+  readonly nestedAssembly: CloudAssembly;
+
+  // Declared in a different file
+}

packages/@aws-cdk/cx-api/lib/cloud-artifact-aug.ts

@@ -0,0 +1,32 @@
+import * as cxschema from '@aws-cdk/cloud-assembly-schema';
+import { AssetManifestArtifact } from './artifacts/asset-manifest-artifact';
+import { CloudFormationStackArtifact } from './artifacts/cloudformation-artifact';
+import { NestedCloudAssemblyArtifact } from './artifacts/nested-cloud-assembly-artifact';
+import { TreeCloudArtifact } from './artifacts/tree-cloud-artifact';
+import { CloudArtifact } from './cloud-artifact';
+import { CloudAssembly } from './cloud-assembly';
+
+/**
+ * Add the 'fromManifest' factory function
+ *
+ * It is defined in a separate file to avoid circular dependencies between 'cloud-artifact.ts'
+ * and all of its subclass files.
+ */
+CloudArtifact.fromManifest = function fromManifest(
+  assembly: CloudAssembly,
+  id: string,
+  artifact: cxschema.ArtifactManifest,
+): CloudArtifact | undefined {
+  switch (artifact.type) {
+    case cxschema.ArtifactType.AWS_CLOUDFORMATION_STACK:
+      return new CloudFormationStackArtifact(assembly, id, artifact);
+    case cxschema.ArtifactType.CDK_TREE:
+      return new TreeCloudArtifact(assembly, id, artifact);
+    case cxschema.ArtifactType.ASSET_MANIFEST:
+      return new AssetManifestArtifact(assembly, id, artifact);
+    case cxschema.ArtifactType.NESTED_CLOUD_ASSEMBLY:
+      return new NestedCloudAssemblyArtifact(assembly, id, artifact);
+    default:
+      return undefined;
+  }
+};

packages/@aws-cdk/cx-api/lib/cloud-artifact.ts

@@ -1,5 +1,5 @@
 import * as cxschema from '@aws-cdk/cloud-assembly-schema';
-import { CloudAssembly } from './cloud-assembly';
+import type { CloudAssembly } from './cloud-assembly';
 import { MetadataEntryResult, SynthesisMessage, SynthesisMessageLevel } from './metadata';
 
 /**
@@ -34,27 +34,6 @@ export interface AwsCloudFormationStackProperties {
  * Represents an artifact within a cloud assembly.
  */
 export class CloudArtifact {
-  /**
-   * Returns a subclass of `CloudArtifact` based on the artifact type defined in the artifact manifest.
-   * @param assembly The cloud assembly from which to load the artifact
-   * @param id The artifact ID
-   * @param artifact The artifact manifest
-   * @returns the `CloudArtifact` that matches the artifact type or `undefined` if it's an artifact type that is unrecognized by this module.
-   */
-  public static fromManifest(assembly: CloudAssembly, id: string, artifact: cxschema.ArtifactManifest): CloudArtifact | undefined {
-    switch (artifact.type) {
-      case cxschema.ArtifactType.AWS_CLOUDFORMATION_STACK:
-        return new CloudFormationStackArtifact(assembly, id, artifact);
-      case cxschema.ArtifactType.CDK_TREE:
-        return new TreeCloudArtifact(assembly, id, artifact);
-      case cxschema.ArtifactType.ASSET_MANIFEST:
-        return new AssetManifestArtifact(assembly, id, artifact);
-      case cxschema.ArtifactType.NESTED_CLOUD_ASSEMBLY:
-        return new NestedCloudAssemblyArtifact(assembly, id, artifact);
-      default:
-        return undefined;
-    }
-  }
 
   /**
    * The artifact's manifest
@@ -153,8 +132,16 @@ export class CloudArtifact {
   }
 }
 
-// needs to be defined at the end to avoid a cyclic dependency
-import { AssetManifestArtifact } from './artifacts/asset-manifest-artifact';
-import { CloudFormationStackArtifact } from './artifacts/cloudformation-artifact';
-import { NestedCloudAssemblyArtifact } from './artifacts/nested-cloud-assembly-artifact';
-import { TreeCloudArtifact } from './artifacts/tree-cloud-artifact';
+export namespace CloudArtifact {
+  /**
+   * Returns a subclass of `CloudArtifact` based on the artifact type defined in the artifact manifest.
+   *
+   * @param assembly The cloud assembly from which to load the artifact
+   * @param id The artifact ID
+   * @param artifact The artifact manifest
+   * @returns the `CloudArtifact` that matches the artifact type or `undefined` if it's an artifact type that is unrecognized by this module.
+   */
+  export declare function fromManifest(assembly: CloudAssembly, id: string, artifact: cxschema.ArtifactManifest): CloudArtifact | undefined;
+
+  // fromManifest function declared in separate file
+}

packages/@aws-cdk/cx-api/lib/index.ts

@@ -7,10 +7,12 @@ export * from './context/endpoint-service-availability-zones';
 export * from './context/security-group';
 export * from './context/key';
 export * from './cloud-artifact';
+import './cloud-artifact-aug';
 export * from './artifacts/asset-manifest-artifact';
 export * from './artifacts/cloudformation-artifact';
 export * from './artifacts/tree-cloud-artifact';
 export * from './artifacts/nested-cloud-assembly-artifact';
+import './artifacts/nested-cloud-assembly-artifact-aug';
 export * from './cloud-assembly';
 export * from './assets';
 export * from './environment';

packages/@aws-cdk/cx-api/package.json

@@ -40,7 +40,7 @@
   "scripts": {
     "build": "cdk-build",
     "watch": "cdk-watch",
-    "lint": "cdk-lint",
+    "lint": "cdk-lint && madge --circular --extensions js lib",
     "test": "cdk-test",
     "pkglint": "pkglint -f",
     "package": "cdk-package",
@@ -72,6 +72,7 @@
     "@types/mock-fs": "^4.13.1",
     "@types/semver": "^7.3.9",
     "jest": "^27.4.7",
+    "madge": "^5.0.1",
     "mock-fs": "^4.14.0"
   },
   "repository": {