chore: add eslint rule to forbid instanceof

packages/@aws-cdk/core/lib/asset-staging.ts

@@ -555,7 +555,7 @@ function calculateCacheKey<A extends object>(props: A): string {
  * Recursively sort object keys
  */
 function sortObject(object: { [key: string]: any }): { [key: string]: any } {
-  if (typeof object !== 'object' || object instanceof Array) {
+  if (typeof object !== 'object' || Array.isArray(object)) {
     return object;
   }
   const ret: { [key: string]: any } = {};

packages/@aws-cdk/core/lib/private/cloudformation-lang.ts

@@ -167,6 +167,7 @@ function tokenAwareStringify(root: any, space: number, ctx: IResolveContext) {
     if (Array.isArray(obj)) {
       return renderCollection('[', ']', obj, recurse);
     }
+    // eslint-disable-next-line no-instanceof/no-instanceof
     if (typeof obj === 'object' && obj != null && !(obj instanceof Date)) {
       // Treat as an intrinsic if this LOOKS like a CFN intrinsic (`{ Ref: ... }`)
       // AND it's the result of a token resolution. Otherwise, we just treat this

packages/@aws-cdk/core/lib/private/resolve.ts

@@ -184,6 +184,7 @@ export function resolve(obj: any, options: IResolveOptions): any {
   // primitives - as-is
   //
 
+  // eslint-disable-next-line no-instanceof/no-instanceof
   if (typeof(obj) !== 'object' || obj instanceof Date) {
     return obj;
   }

packages/@aws-cdk/core/lib/private/synthesis.ts

@@ -182,7 +182,7 @@ function synthesizeTree(root: IConstruct, builder: cxapi.CloudAssemblyBuilder, v
 
     if (Stack.isStack(construct)) {
       construct.synthesizer.synthesize(session);
-    } else if (construct instanceof TreeMetadata) {
+    } else if (TreeMetadata.isTreeMetadata(construct)) {
       construct._synthesizeTree(session);
     } else {
       const custom = getCustomSynthesis(construct);

packages/@aws-cdk/core/lib/private/tree-metadata.ts

@@ -10,13 +10,22 @@ import { ConstructInfo, constructInfoFromConstruct } from './runtime-info';
 
 const FILE_PATH = 'tree.json';
 
+const TREE_METADATA_SYMBOL = Symbol.for('@aws-cdk/core.TreeMetadata');
+
 /**
  * Construct that is automatically attached to the top-level `App`.
  * This generates, as part of synthesis, a file containing the construct tree and the metadata for each node in the tree.
  * The output is in a tree format so as to preserve the construct hierarchy.
  *
  */
 export class TreeMetadata extends Construct {
+  /**
+   * Return whether the given object is a TreeMetadata.
+   */
+  public static isTreeMetadata(x: any): x is TreeMetadata {
+    return x !== null && typeof(x) === 'object' && TREE_METADATA_SYMBOL in x;
+  }
+
   constructor(scope: Construct) {
     super(scope, 'Tree');
   }
@@ -98,3 +107,12 @@ interface Node {
    */
   readonly constructInfo?: ConstructInfo;
 }
+
+/**
+ * Mark all instances of 'TreeMetadata'.
+ */
+Object.defineProperty(TreeMetadata.prototype, TREE_METADATA_SYMBOL, {
+  value: true,
+  enumerable: false,
+  writable: false,
+});

packages/@aws-cdk/core/lib/runtime.ts

@@ -231,6 +231,7 @@ export function validateBoolean(x: any): ValidationResult {
 }
 
 export function validateDate(x: any): ValidationResult {
+  // eslint-disable-next-line no-instanceof/no-instanceof
   if (canInspect(x) && !(x instanceof Date)) {
     return new ValidationResult(`${JSON.stringify(x)} should be a Date`);
   }

packages/@aws-cdk/core/test/stack-synthesis/clicreds-synthesis.test.ts

@@ -239,7 +239,7 @@ function evalCFN(value: any) {
 }
 
 function isAssetManifest(x: cxapi.CloudArtifact): x is cxapi.AssetManifestArtifact {
-  return x instanceof cxapi.AssetManifestArtifact;
+  return cxapi.AssetManifestArtifact.isAssetManifestArtifact(x);
 }
 
 function getAssetManifest(asm: cxapi.CloudAssembly): cxapi.AssetManifestArtifact {

packages/@aws-cdk/core/test/stack-synthesis/new-style-synthesis.test.ts

@@ -393,7 +393,7 @@ function evalCFN(value: any) {
 }
 
 function isAssetManifest(x: cxapi.CloudArtifact): x is cxapi.AssetManifestArtifact {
-  return x instanceof cxapi.AssetManifestArtifact;
+  return cxapi.AssetManifestArtifact.isAssetManifestArtifact(x);
 }
 
 function getAssetManifest(asm: cxapi.CloudAssembly): cxapi.AssetManifestArtifact {

packages/@aws-cdk/core/test/stage.test.ts

@@ -50,7 +50,7 @@ describe('stage', () => {
     // THEN -- app manifest contains a nested cloud assembly
     const appAsm = app.synth();
 
-    const artifact = appAsm.artifacts.find(x => x instanceof cxapi.NestedCloudAssemblyArtifact);
+    const artifact = appAsm.artifacts.find(x => cxapi.NestedCloudAssemblyArtifact.isNestedCloudAssemblyArtifact(x));
     expect(artifact).toBeDefined();
 
 

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

@@ -5,7 +5,16 @@ import { CloudArtifact } from '../cloud-artifact';
 import type { CloudAssembly } from '../cloud-assembly';
 import { Environment, EnvironmentUtils } from '../environment';
 
+const CLOUDFORMATION_STACK_ARTIFACT_SYMBOL = Symbol.for('@aws-cdk/cx-api.CloudFormationStackArtifact');
+
 export class CloudFormationStackArtifact extends CloudArtifact {
+  /**
+   * Return whether the given object is a CloudFormationStackArtifact.
+   */
+  public static isCloudFormationStackArtifact(x: any): x is CloudFormationStackArtifact {
+    return x !== null && typeof(x) === 'object' && CLOUDFORMATION_STACK_ARTIFACT_SYMBOL in x;
+  }
+
   /**
    * The file name of the template.
    */
@@ -183,3 +192,12 @@ export class CloudFormationStackArtifact extends CloudArtifact {
     return ret;
   }
 }
+
+/**
+ * Mark all instances of 'CloudFormationStackArtifact'.
+ */
+Object.defineProperty(CloudFormationStackArtifact.prototype, CLOUDFORMATION_STACK_ARTIFACT_SYMBOL, {
+  value: true,
+  enumerable: false,
+  writable: false,
+});

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

@@ -3,10 +3,19 @@ import * as cxschema from '@aws-cdk/cloud-assembly-schema';
 import { CloudArtifact } from '../cloud-artifact';
 import type { CloudAssembly } from '../cloud-assembly';
 
+const NESTED_CLOUD_ASSEMBLY_ARTIFACT_SYMBOL = Symbol.for('@aws-cdk/cx-api.NestedCloudAssemblyArtifact');
+
 /**
  * Asset manifest is a description of a set of assets which need to be built and published
  */
 export class NestedCloudAssemblyArtifact extends CloudArtifact {
+  /**
+   * Return whether the given object is a NestedCloudAssemblyArtifact.
+   */
+  public static isNestedCloudAssemblyArtifact(x: any): x is NestedCloudAssemblyArtifact {
+    return x !== null && typeof(x) === 'object' && NESTED_CLOUD_ASSEMBLY_ARTIFACT_SYMBOL in x;
+  }
+
   /**
    * The relative directory name of the asset manifest
    */
@@ -40,4 +49,13 @@ export interface NestedCloudAssemblyArtifact {
   readonly nestedAssembly: CloudAssembly;
 
   // Declared in a different file
-}
+}
+
+/**
+ * Mark all instances of 'NestedCloudAssemblyArtifact'.
+ */
+Object.defineProperty(NestedCloudAssemblyArtifact.prototype, NESTED_CLOUD_ASSEMBLY_ARTIFACT_SYMBOL, {
+  value: true,
+  enumerable: false,
+  writable: false,
+});

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

@@ -2,7 +2,16 @@ import * as cxschema from '@aws-cdk/cloud-assembly-schema';
 import { CloudArtifact } from '../cloud-artifact';
 import { CloudAssembly } from '../cloud-assembly';
 
+const TREE_CLOUD_ARTIFACT_SYMBOL = Symbol.for('@aws-cdk/cx-api.TreeCloudArtifact');
+
 export class TreeCloudArtifact extends CloudArtifact {
+  /**
+   * Return whether the given object is a TreeCloudArtifact.
+   */
+  public static isTreeCloudArtifact(x: any): x is TreeCloudArtifact {
+    return x !== null && typeof(x) === 'object' && TREE_CLOUD_ARTIFACT_SYMBOL in x;
+  }
+
   public readonly file: string;
 
   constructor(assembly: CloudAssembly, name: string, artifact: cxschema.ArtifactManifest) {
@@ -14,4 +23,13 @@ export class TreeCloudArtifact extends CloudArtifact {
     }
     this.file = properties.file;
   }
-}
+}
+
+/**
+ * Mark all instances of 'TreeCloudArtifact'.
+ */
+Object.defineProperty(TreeCloudArtifact.prototype, TREE_CLOUD_ARTIFACT_SYMBOL, {
+  value: true,
+  enumerable: false,
+  writable: false,
+});

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

@@ -80,7 +80,7 @@ export class CloudAssembly {
    * @returns a `CloudFormationStackArtifact` object.
    */
   public getStackByName(stackName: string): CloudFormationStackArtifact {
-    const artifacts = this.artifacts.filter(a => a instanceof CloudFormationStackArtifact && a.stackName === stackName);
+    const artifacts = this.artifacts.filter(a => CloudFormationStackArtifact.isCloudFormationStackArtifact(a) && a.stackName === stackName);
     if (!artifacts || artifacts.length === 0) {
       throw new Error(`Unable to find stack with stack name "${stackName}"`);
     }
@@ -115,7 +115,7 @@ export class CloudAssembly {
       throw new Error(`Unable to find artifact with id "${artifactId}"`);
     }
 
-    if (!(artifact instanceof CloudFormationStackArtifact)) {
+    if (!CloudFormationStackArtifact.isCloudFormationStackArtifact(artifact)) {
       throw new Error(`Artifact ${artifactId} is not a CloudFormation stack`);
     }
 
@@ -154,7 +154,7 @@ export class CloudAssembly {
       throw new Error(`Unable to find artifact with id "${artifactId}"`);
     }
 
-    if (!(artifact instanceof NestedCloudAssemblyArtifact)) {
+    if (!NestedCloudAssemblyArtifact.isNestedCloudAssemblyArtifact(artifact)) {
       throw new Error(`Found artifact '${artifactId}' but it's not a nested cloud assembly`);
     }
 
@@ -184,7 +184,7 @@ export class CloudAssembly {
     }
     const tree = trees[0];
 
-    if (!(tree instanceof TreeCloudArtifact)) {
+    if (!TreeCloudArtifact.isTreeCloudArtifact(tree)) {
       throw new Error('"Tree" artifact is not of expected type');
     }
 
@@ -195,22 +195,14 @@ export class CloudAssembly {
    * @returns all the CloudFormation stack artifacts that are included in this assembly.
    */
   public get stacks(): CloudFormationStackArtifact[] {
-    return this.artifacts.filter(isCloudFormationStackArtifact);
-
-    function isCloudFormationStackArtifact(x: any): x is CloudFormationStackArtifact {
-      return x instanceof CloudFormationStackArtifact;
-    }
+    return this.artifacts.filter(CloudFormationStackArtifact.isCloudFormationStackArtifact);
   }
 
   /**
    * The nested assembly artifacts in this assembly
    */
   public get nestedAssemblies(): NestedCloudAssemblyArtifact[] {
-    return this.artifacts.filter(isNestedCloudAssemblyArtifact);
-
-    function isNestedCloudAssemblyArtifact(x: any): x is NestedCloudAssemblyArtifact {
-      return x instanceof NestedCloudAssemblyArtifact;
-    }
+    return this.artifacts.filter(NestedCloudAssemblyArtifact.isNestedCloudAssemblyArtifact);
   }
 
   private validateDeps() {

tools/@aws-cdk/cdk-build-tools/config/eslintrc.js

@@ -17,6 +17,7 @@ module.exports = {
     'import',
     '@aws-cdk',
     'jest',
+    'no-instanceof',
   ],
   parser: '@typescript-eslint/parser',
   parserOptions: {
@@ -199,6 +200,10 @@ module.exports = {
       ],
     }],
 
+    // 'instanceof' must be avoided, it cannot be made to work properly in the face of symlinks and transitive dependencies
+    // (it may only be used for built-ins and classes that are guaranteed to not escape the scope)
+    'no-instanceof/no-instanceof': 'error',
+
     // Overrides for plugin:jest/recommended
     "jest/expect-expect": "off",
     "jest/no-conditional-expect": "off",

tools/@aws-cdk/cdk-build-tools/package.json

@@ -47,6 +47,7 @@
     "@aws-cdk/node-bundle": "0.0.0",
     "@typescript-eslint/eslint-plugin": "^4.33.0",
     "@typescript-eslint/parser": "^4.33.0",
+    "eslint-plugin-no-instanceof": "^1.0.1",
     "awslint": "0.0.0",
     "chalk": "^4",
     "eslint": "^7.32.0",

tools/@aws-cdk/cfn2ts/lib/genspec.ts

@@ -111,7 +111,7 @@ export class Attribute {
  * Example: AWS::EC2 -> ec2
  */
 export function packageName(module: SpecName | string): string {
-  if (module instanceof SpecName) {
+  if (SpecName.isSpecName(module)) {
     module = module.module;
   }
 

tools/@aws-cdk/cfn2ts/lib/spec-utils.ts

@@ -1,12 +1,21 @@
 import { schema } from '@aws-cdk/cfnspec';
 import { joinIf } from './util';
 
+const SPEC_NAME_SYMBOL = Symbol.for('@aws-cdk/cfn2ts.SpecName');
+
 /**
  * Name of an object in the CloudFormation spec
  *
  * This refers to a Resource, parsed from a string like 'AWS::S3::Bucket'.
  */
 export class SpecName {
+  /**
+   * Return whether the given object is a SpecName.
+   */
+  public static isSpecName(x: any): x is SpecName {
+    return x !== null && typeof(x) === 'object' && SPEC_NAME_SYMBOL in x;
+  }
+
   /**
    * Parse a string representing a name from the CloudFormation spec to a CfnName object
    */
@@ -36,6 +45,7 @@ export class SpecName {
   }
 }
 
+
 /**
  * Name of a property type or attribute in the CloudFormation spec.
  *
@@ -121,3 +131,12 @@ function primitiveScalarTypeNames(spec: schema.ScalarProperty): string[] {
   }
   return [];
 }
+
+/**
+ * Mark all instances of 'SpecName'.
+ */
+Object.defineProperty(SpecName.prototype, SPEC_NAME_SYMBOL, {
+  value: true,
+  enumerable: false,
+  writable: false,
+});

yarn.lock

@@ -4538,6 +4538,11 @@ eslint-plugin-jest@^24.7.0:
   dependencies:
     "@typescript-eslint/experimental-utils" "^4.0.1"
 
+eslint-plugin-no-instanceof@^1.0.1:
+  version "1.0.1"
+  resolved "https://registry.npmjs.org/eslint-plugin-no-instanceof/-/eslint-plugin-no-instanceof-1.0.1.tgz#5d9fc86d160df6991b654b294a62390207f1bb97"
+  integrity sha512-zlqQ7EsfzbRO68uI+p8FIE7zYB4njs+nNbkNjSb5QmLi2et67zQLqSeaao5U9SpnlZTTJC87nS2oyHo2ACtajw==
+
 eslint-plugin-node@^11.1.0:
   version "11.1.0"
   resolved "https://registry.npmjs.org/eslint-plugin-node/-/eslint-plugin-node-11.1.0.tgz#c95544416ee4ada26740a30474eefc5402dc671d"