chore: require type imports in published packages to be from declared dependencies (#472)

When we import a type, this import may become part of the public
declarations of a package. Previously we allowed types to be imported
from devDeps. This can cause consuming TypeScript packages to fail
compilation if they have `skipLibCheck: false` set (which is the
default).

To resolve this, we are now enforcing all type imports to be from a
declared dependency. The recommendation is to declare a very wide peer
dependency, if the package is a types only package.

Note that not all imports of types will actually end up in the published
declaration files. This only happens if the imported type is part of an
exported API for that file, e.g. part of a function signature.
Unfortunately there is no good way of checking just this case with
eslint, so we do the next best thing.

---
By submitting this pull request, I confirm that my contribution is made
under the terms of the Apache-2.0 license

Author: mrgrain

.projenrc.ts

@@ -7,7 +7,7 @@ import { AdcPublishing } from './projenrc/adc-publishing';
 import { BundleCli } from './projenrc/bundle';
 import { CdkCliIntegTestsWorkflow } from './projenrc/cdk-cli-integ-tests';
 import { CodeCovWorkflow } from './projenrc/codecov';
-import { ESLINT_RULES } from './projenrc/eslint';
+import { configureEslint } from './projenrc/eslint';
 import { IssueLabeler } from './projenrc/issue-labeler';
 import { JsiiBuild } from './projenrc/jsii';
 import { LargePrChecker } from './projenrc/large-pr-checker';
@@ -21,54 +21,32 @@ import { TypecheckTests } from './projenrc/TypecheckTests';
 const TYPESCRIPT_VERSION = '5.6';
 
 /**
- * Projen depends on TypeScript-eslint 7 by default.
- *
- * We want 8 for the parser, and 6 for the plugin (because after 6 some linter
- * rules we are relying on have been moved to another plugin).
- *
- * Also configure eslint plugins & rules, which cannot be configured by props.
+ * Configures a Eslint, which is a complex setup.
  *
  * We also need to override the built-in prettier dependency to prettier@2, because
  * Jest < 30 can only work with prettier 2 (https://github.com/jestjs/jest/issues/14305)
  * and 30 is not stable yet.
  */
 function configureProject<A extends pj.typescript.TypeScriptProject>(x: A): A {
+  // currently supported min node version
   x.package.addEngine('node', '>= 14.15.0');
+
   x.addDevDeps(
-    '@typescript-eslint/eslint-plugin@^8',
-    '@typescript-eslint/parser@^8',
-    '@stylistic/eslint-plugin@^3',
-    '@cdklabs/eslint-plugin',
-    'eslint-plugin-import',
-    'eslint-plugin-jest',
-    'eslint-plugin-jsdoc',
     'jest-junit@^16',
+    'prettier@^2.8',
   );
-  x.eslint?.addPlugins(
-    '@typescript-eslint',
-    'import',
-    '@cdklabs',
-    '@stylistic',
-    'jest',
-    'jsdoc',
-  );
-  x.eslint?.addExtends(
-    'plugin:jest/recommended',
-  );
-  x.eslint?.addIgnorePattern('*.generated.ts');
-  x.eslint?.addRules(ESLINT_RULES);
-
-  // Prettier needs to be turned off for now, there's too much code that doesn't conform to it
-  x.eslint?.addRules({ 'prettier/prettier': ['off'] });
 
-  x.addDevDeps('prettier@^2.8');
+  configureEslint(x);
 
-  x.npmignore?.addPatterns('.eslintrc.js');
-  // As a rule we don't include .ts sources in the NPM package
-  x.npmignore?.addPatterns('*.ts', '!*.d.ts');
-
-  // Never include the build-tools directory
-  x.npmignore?.addPatterns('build-tools');
+  x.npmignore?.addPatterns(
+    // don't inlcude config files
+    '.eslintrc.js',
+    // As a rule we don't include .ts sources in the NPM package
+    '*.ts',
+    '!*.d.ts',
+    // Never include the build-tools directory
+    'build-tools',
+  );
 
   if (x instanceof TypeScriptWorkspace) {
     // Individual workspace packages shouldn't depend on "projen", it gets brought in at the monorepo root

packages/@aws-cdk-testing/cli-integ/.eslintrc.json

@@ -2,7 +2,6 @@
 /* eslint-disable @typescript-eslint/no-var-requires */
 import * as fs from 'fs';
 import * as path from 'path';
-import type { ForReading } from '@aws-cdk/cli-plugin-contract';
 import type { Environment } from '@aws-cdk/cx-api';
 import { UNKNOWN_ACCOUNT, UNKNOWN_REGION } from '@aws-cdk/cx-api';
 import type {
@@ -24,6 +23,7 @@ import { ToolkitError } from '../../../@aws-cdk/toolkit-lib';
 import { info } from '../../lib/logging';
 import type { ICloudFormationClient, SdkProvider } from '../api/aws-auth';
 import { CloudFormationStack } from '../api/cloudformation';
+import { Mode } from '../api/plugin';
 import { zipDirectory } from '../util';
 const camelCase = require('camelcase');
 const decamelize = require('decamelize');
@@ -143,7 +143,7 @@ export async function readFromStack(
   sdkProvider: SdkProvider,
   environment: Environment,
 ): Promise<string | undefined> {
-  const cloudFormation = (await sdkProvider.forEnvironment(environment, 0 satisfies ForReading)).sdk.cloudFormation();
+  const cloudFormation = (await sdkProvider.forEnvironment(environment, Mode.ForReading)).sdk.cloudFormation();
 
   const stack = await CloudFormationStack.lookup(cloudFormation, stackName, true);
   if (stack.stackStatus.isDeploySuccess || stack.stackStatus.isRollbackSuccess) {
@@ -605,7 +605,7 @@ export function buildGenertedTemplateOutput(
  * @returns A CloudFormation sdk client
  */
 export async function buildCfnClient(sdkProvider: SdkProvider, environment: Environment) {
-  const sdk = (await sdkProvider.forEnvironment(environment, 0 satisfies ForReading)).sdk;
+  const sdk = (await sdkProvider.forEnvironment(environment, Mode.ForReading)).sdk;
   sdk.appendCustomUserAgent('cdk-migrate');
   return sdk.cloudFormation();
 }

packages/@aws-cdk/cli-lib-alpha/.eslintrc.json

@@ -1,3 +1,5 @@
+import { yarn } from 'cdklabs-projen-project-types';
+import type { typescript } from 'projen';
 import bestPractices from './best-practices';
 import constructs from './constructs';
 import formatting from './formatting';
@@ -6,12 +8,61 @@ import jest from './jest';
 import jsdoc from './jsdoc';
 import team from './team';
 
-export const ESLINT_RULES = {
+const ESLINT_RULES = {
   ...team,
   ...bestPractices,
   ...constructs,
   ...imports,
   ...formatting,
   ...jsdoc,
   ...jest,
+
+  // Prettier needs to be turned off for now, there's too much code that doesn't conform to it
+  'prettier/prettier': ['off'],
 };
+
+/**
+ * Projen depends on TypeScript-eslint 7 by default.
+ *
+ * We want 8 for the parser, and 6 for the plugin (because after 6 some linter
+ * rules we are relying on have been moved to another plugin).
+ *
+ * Also configure eslint plugins & rules, which cannot be configured by props.
+ */
+export function configureEslint(x: typescript.TypeScriptProject) {
+  const isRoot = x instanceof yarn.Monorepo;
+  const isPrivate = x instanceof yarn.TypeScriptWorkspace && x.isPrivatePackage;
+
+  // configure deps and plugins
+  x.addDevDeps(
+    '@typescript-eslint/eslint-plugin@^8',
+    '@typescript-eslint/parser@^8',
+    '@stylistic/eslint-plugin@^3',
+    '@cdklabs/eslint-plugin',
+    'eslint-plugin-import',
+    'eslint-plugin-jest',
+    'eslint-plugin-jsdoc',
+  );
+  x.eslint?.addPlugins(
+    '@typescript-eslint',
+    'import',
+    '@cdklabs',
+    '@stylistic',
+    'jest',
+    'jsdoc',
+  );
+
+  // ignore files
+  x.eslint?.addIgnorePattern('*.generated.ts');
+
+  // base rules from plugins and our sets
+  x.eslint?.addExtends(
+    'plugin:jest/recommended',
+  );
+  x.eslint?.addRules(ESLINT_RULES);
+
+  // For our published packages, we need all type imports to be from a public dependency
+  if (!isRoot && !isPrivate && x.eslint) {
+    x.eslint.rules['import/no-extraneous-dependencies'][1].includeTypes = true;
+  }
+}