Merge branch 'master' into bump-cfnspec/v30.0.0

aws · Mar 3, 2021 · af4859b · af4859b
2 parents 70060fe + 2c074de
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diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
@@ -14,6 +14,7 @@ and let us know if it's not up-to-date (even better, submit a PR with your  corr
   - [Step 4: Commit](#step-4-commit)
   - [Step 5: Pull Request](#step-5-pull-request)
   - [Step 6: Merge](#step-6-merge)
+- [Breaking Changes](#breaking-changes)
 - [Tools](#tools)
   - [Main build scripts](#main-build-scripts)
   - [Partial build tools](#partial-build-tools)
@@ -266,6 +267,143 @@ BREAKING CHANGE: Description of what broke and how to achieve this behavior now
 * Once approved and tested, a maintainer will squash-merge to master and will use your PR title/description as the
   commit message.
 
+## Breaking Changes
+
+Whenever you are making changes, there is a chance for those changes to be
+*breaking* existing users of the library. A change is breaking if there are
+programs that customers could have been writing against the current version
+of the CDK, that will no longer "work correctly" with the proposed new
+version of the CDK.
+
+Breaking changes are not allowed in *stable* libraries¹. They are permissible
+but still *highly discouraged* in experimental libraries, and require explicit
+callouts in the bodies of Pull Requests that introduce them.
+
+> ¹) Note that starting in version 2 of the CDK, the majority of library code will be
+> bundled into a single main CDK library which will be considered stable, and so
+> no code in there can undergo breaking changes.
+
+Breaking changes come in two flavors:
+
+* API surface changes
+* Behavior changes
+
+### API surface changes
+
+This encompasses any changes that affect the shape of the API. Changes that
+will make existing programs fail to compile are not allowed. Typical examples
+of that are:
+
+* Renaming classes or methods
+* Adding required properties to a struct that is used as an input to a constructor
+  or method. This also includes changing a type from nullable to non-nullable.
+* Removing properties from a struct that is returned from a method, or removing
+  properties from a class. This also includes changing a type from non-nullable
+  to nullable.
+
+To see why the latter is a problem, consider the following class:
+
+```ts
+class SomeClass {
+  public readonly count: number;
+  //               ❓ let's say I want to change this to 'count?: number',
+  //                  i.e. make it optional.
+}
+
+// Someone could have written the following code:
+const obj = new SomeClass();
+console.log(obj.count + 1);
+
+// After the proposed change, this code that used to compile fine will now throw:
+console.log(obj.count + 1);
+//          ~~~~~~~~~ Error: Object is possibly 'undefined'.
+```
+
+CDK comes with build tooling to check whether changes you made introduce breaking
+changes to the API surface. In a package directory, run:
+
+```shell
+$ yarn build
+$ yarn compat
+```
+
+To figure out if the changes you made were breaking. See the section [API Compatibility
+Checks](#api-compatibility-checks) for more information.
+
+#### Dealing with breaking API surface changes
+
+If you need to change the type of some API element, introduce a new API
+element and mark the old API element as `@deprecated`.
+
+If you need to pretend to have a value for the purposes of implementing an API
+and you don't actually have a useful value to return, it is acceptable to make
+the property a `getter` and throw an exception (keeping in mind to write error
+messages that will be useful to a user of your construct):
+
+```ts
+class SomeClass implements ICountable {
+  constructor(private readonly _count?: number) {
+  }
+
+  public get count(): number {
+    if (this._count === undefined) {
+      // ✅ DO: throw a descriptive error that tells the user what to do
+      throw new Error('This operation requires that a \'count\' is specified when SomeClass is created.');
+      // ❌ DO NOT: just throw an error like 'count is missing'
+    }
+    return this._count;
+  }
+}
+```
+
+### Behavior changes
+
+These are changes that do not directly affect the compilation of programs
+written against the previous API, but may change their meaning. In practice,
+even though the user didn't change their code, the CloudFormation template
+that gets synthesized is now different.
+
+**Not all template changes are breaking changes!** Consider a user that has
+created a Stack using the previous version of the library, has updated their
+version of the CDK library and is now deploying an update. A behavior change
+is breaking if:
+
+* The update cannot be applied at all
+* The update can be applied but causes service interruption or data loss.
+
+Data loss happens when the [Logical
+ID](https://docs.aws.amazon.com/cdk/latest/guide/identifiers.html#identifiers_logical_ids)
+of a stateful resource changes, or one of the [resource properties that requires
+replacement](https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/using-cfn-updating-stacks-update-behaviors.html)
+is modified. In both of these cases, CloudFormation will delete the
+resource, and if it was a stateful resource like a database the data in it is now gone.
+
+If a change applies cleanly and does not cause any service interruption, it
+is not breaking. Nevertheless, it might still be wise to avoid those kinds of
+changes as users are understandably wary of unexpected template changes, will
+scrutinize them heavily, and we don't want to cause unnecessary panic and churn
+in our use base.
+
+Determining whether or not behavioral changes are breaking requires expertise
+and judgement on the part of the library owner, and testing.
+
+#### Dealing with breaking behavior changes
+
+Most of the time, behavioral changes will arise because we want to change the
+default value or default behavior of some property (i.e., we want to change the
+interpretation of what it means if the value is missing).
+
+If the new behavior is going to be breaking, the user must opt in to it, either by:
+
+* Adding a new API element (class, property, method, ...) to have users
+  explicitly opt in to the new behavior at the source code level (potentially
+  `@deprecate`ing the old API element); or
+* Use the [feature flag](#feature-flags) mechanism to have the user opt in to the new
+  behavior without changing the source code.
+
+Of these two, the first one is preferred if possible (as feature flags have
+non-local effects which can cause unintended effects).
+
 ## Tools
 
 The CDK is a big project, and at the moment, all of the CDK modules are mastered in a single monolithic repository

diff --git a/DESIGN_GUIDELINES.md b/DESIGN_GUIDELINES.md
@@ -1,65 +1,5 @@
 # AWS Construct Library Design Guidelines
 
-- [AWS Construct Library Design Guidelines](#aws-construct-library-design-guidelines)
-  - [What's Included](#what-s-included)
-  - [API Design](#api-design)
-    - [Modules](#modules)
-    - [Construct Class](#construct-class)
-    - [Construct Interface](#construct-interface)
-      - [Owned vs. Unowned Constructs](#owned-vs-unowned-constructs)
-      - [Abstract Base](#abstract-base)
-    - [Props](#props)
-      - [Types](#types)
-      - [Defaults](#defaults)
-      - [Flat](#flat)
-      - [Concise](#concise)
-      - [Naming](#naming)
-      - [Property Documentation](#property-documentation)
-      - [Enums](#enums)
-      - [Unions](#unions)
-    - [Attributes](#attributes)
-    - [Configuration](#configuration)
-      - [Prefer Additions](#prefer-additions)
-      - [Dropped Mutations](#dropped-mutations)
-    - [Factories](#factories)
-    - [Imports](#imports)
-      - [“from” Methods](#-from--methods)
-      - [From-attributes](#from-attributes)
-    - [Roles](#roles)
-    - [Resource Policies](#resource-policies)
-    - [VPC](#vpc)
-    - [Grants](#grants)
-    - [Metrics](#metrics)
-    - [Events](#events)
-    - [Connections](#connections)
-    - [Integrations](#integrations)
-    - [State](#state)
-    - [Physical Names - TODO](#physical-names---todo)
-    - [Tags](#tags)
-    - [Secrets](#secrets)
-  - [Project Structure](#project-structure)
-    - [Code Organization](#code-organization)
-  - [Implementation](#implementation)
-    - [General Principles](#general-principles)
-    - [Construct IDs](#construct-ids)
-    - [Errors](#errors)
-      - [Input Validation](#input-validation)
-      - [Avoid Errors If Possible](#avoid-errors-if-possible)
-      - [Never Catch Exceptions](#never-catch-exceptions)
-      - [Post Validation](#post-validation)
-      - [Attached Errors/Warnings](#attached-errors-warnings)
-    - [Tokens](#tokens)
-  - [Documentation](#documentation)
-    - [Inline Documentation](#inline-documentation)
-    - [Readme](#readme)
-  - [Testing](#testing)
-    - [Unit tests](#unit-tests)
-    - [Integration tests](#integration-tests)
-    - [Versioning](#versioning)
-  - [Naming & Style](#naming---style)
-    - [Naming Conventions](#naming-conventions)
-    - [Coding Style](#coding-style)
-
 The AWS Construct Library is a rich class library of CDK constructs which
 represent all resources offered by the AWS Cloud and higher-level constructs for
 achieving common tasks.
@@ -68,6 +8,68 @@ The purpose of this document is to provide guidelines for designing the APIs in
 the AWS Construct Library in order to ensure a consistent and integrated
 experience across the entire AWS surface area.
 
+* [Preface](#preface)
+* [What's Included](#what-s-included)
+* [API Design](#api-design)
+  * [Modules](#modules)
+  * [Construct Class](#construct-class)
+  * [Construct Interface](#construct-interface)
+    * [Owned vs. Unowned Constructs](#owned-vs-unowned-constructs)
+    * [Abstract Base](#abstract-base)
+  * [Props](#props)
+    * [Types](#types)
+    * [Defaults](#defaults)
+    * [Flat](#flat)
+    * [Concise](#concise)
+    * [Naming](#naming)
+    * [Property Documentation](#property-documentation)
+    * [Enums](#enums)
+    * [Unions](#unions)
+  * [Attributes](#attributes)
+  * [Configuration](#configuration)
+    * [Prefer Additions](#prefer-additions)
+    * [Dropped Mutations](#dropped-mutations)
+  * [Factories](#factories)
+  * [Imports](#imports)
+    * [“from” Methods](#-from--methods)
+    * [From-attributes](#from-attributes)
+  * [Roles](#roles)
+  * [Resource Policies](#resource-policies)
+  * [VPC](#vpc)
+  * [Grants](#grants)
+  * [Metrics](#metrics)
+  * [Events](#events)
+  * [Connections](#connections)
+  * [Integrations](#integrations)
+  * [State](#state)
+  * [Physical Names - TODO](#physical-names---todo)
+  * [Tags](#tags)
+  * [Secrets](#secrets)
+* [Project Structure](#project-structure)
+  * [Code Organization](#code-organization)
+* [Implementation](#implementation)
+  * [General Principles](#general-principles)
+  * [Construct IDs](#construct-ids)
+  * [Errors](#errors)
+    * [Avoid Errors If Possible](#avoid-errors-if-possible)
+    * [Error reporting mechanism](#error-reporting-mechanism)
+    * [Throwing exceptions](#throwing-exceptions)
+    * [Never Catch Exceptions](#never-catch-exceptions)
+    * [Attaching (lazy) Validators](#attaching--lazy--validators)
+    * [Attaching Errors/Warnings](#attaching-errors-warnings)
+    * [Error messages](#error-messages)
+  * [Tokens](#tokens)
+* [Documentation](#documentation)
+  * [Inline Documentation](#inline-documentation)
+  * [Readme](#readme)
+* [Testing](#testing)
+  * [Unit tests](#unit-tests)
+  * [Integration tests](#integration-tests)
+  * [Versioning](#versioning)
+* [Naming & Style](#naming---style)
+  * [Naming Conventions](#naming-conventions)
+  * [Coding Style](#coding-style)
+
 ## Preface
 
 As much as possible, the guidelines in this document are enforced using the

diff --git a/packages/@aws-cdk/aws-apigateway/lib/domain-name.ts b/packages/@aws-cdk/aws-apigateway/lib/domain-name.ts
@@ -12,8 +12,9 @@ import { EndpointType, IRestApi } from './restapi';
 export enum SecurityPolicy {
   /** Cipher suite TLS 1.0 */
   TLS_1_0 = 'TLS_1_0',
+
   /** Cipher suite TLS 1.2 */
-  TLS_1_2 = 'TLS_1_2'
+  TLS_1_2 = 'TLS_1_2',
 }
 
 export interface DomainNameOptions {
@@ -40,13 +41,13 @@ export interface DomainNameOptions {
    * @see https://docs.aws.amazon.com/AWSCloudFormation/latest/UserGuide/aws-resource-apigateway-domainname.html
    * @default SecurityPolicy.TLS_1_0
    */
-  readonly securityPolicy?: SecurityPolicy
+  readonly securityPolicy?: SecurityPolicy;
 
   /**
    * The mutual TLS authentication configuration for a custom domain name.
    * @default - mTLS is not configured.
    */
-  readonly mtls?: MTLSConfig
+  readonly mtls?: MTLSConfig;
 }
 
 export interface DomainNameProps extends DomainNameOptions {
@@ -83,7 +84,6 @@ export interface IDomainName extends IResource {
    * @attribute DistributionHostedZoneId,RegionalHostedZoneId
    */
   readonly domainNameAliasHostedZoneId: string;
-
 }
 
 export class DomainName extends Resource implements IDomainName {
@@ -112,9 +112,9 @@ export class DomainName extends Resource implements IDomainName {
     const edge = endpointType === EndpointType.EDGE;
 
     if (!Token.isUnresolved(props.domainName) && /[A-Z]/.test(props.domainName)) {
-      throw new Error('domainName does not support uppercase letters. ' +
-        `got: '${props.domainName}'`);
+      throw new Error(`Domain name does not support uppercase letters. Got: ${props.domainName}`);
     }
+
     const mtlsConfig = this.configureMTLS(props.mtls);
     const resource = new CfnDomainName(this, 'Resource', {
       domainName: props.domainName,
@@ -176,10 +176,9 @@ export interface DomainNameAttributes {
   readonly domainNameAliasTarget: string;
 
   /**
-   * Thje Route53 hosted zone ID to use in order to connect a record set to this domain through an alias.
+   * The Route53 hosted zone ID to use in order to connect a record set to this domain through an alias.
    */
   readonly domainNameAliasHostedZoneId: string;
-
 }
 
 /**
@@ -190,8 +189,9 @@ export interface MTLSConfig {
    * The bucket that the trust store is hosted in.
    */
   readonly bucket: IBucket;
+
   /**
-   * The key in S3 to look at for the trust store
+   * The key in S3 to look at for the trust store.
    */
   readonly key: string;